Architectural Information Modeling (AIM): Teaching Formal Concepts of Design Using Building Information Modeling (BIM)

Alassaf, Nancy Salman Mohammad Texas A&M University ProQuest Dissertations & Thes 2019 해외박사(DDOD)

This research focuses on overcoming the difficulties of using BIM in conceptual design. It suggests that incorporating formal knowledge with computational concepts within BIM enables the tool to support the conceptual design process. This research used a mixed-methods approach that comprised of historical-interpretive research, model-based inquiry, and quasi-experimental research. First, a computational framework called Architectural Information modeling (AIM) was developed. AIM is a computational design framework that uses BIM to represent a formal language explicitly and provide a generative description of an architectural style. It employs various strategies to define conceptual design vocabularies and syntactical rules. In AIM, a direct connection between the abstract diagram and the actual built form is established. Second, the formal language of Richard Meier was selected as a test case. AIM was used to code the language of the Douglas house and generate the Smith house from the same model. Moreover, various other options that have the same formal language were created using the same model. The notion of stylistic change was explored too. Second, architectural design pedagogy was selected as an area of exploration to validate AIM. A pedagogical framework to teach AIM was developed to conduct a quasi-experimental study in the form of a longitudinal study. At the College of Architecture at Texas A&M University, three second-year design studios (38 students) participated in this intervention study. Data were collected through observations, student survey, student writing assignments, and student projects. Descriptive and inferential statistical methods, content analysis, and a panel of experts were used to analyze the data. The findings of the study illustrate that AIM can provide a shift from BIM as a construction-oriented modeling environment to a design environment where the architect can think, design, and generate multiple design options that incorporate explicit aesthetic and intellectual values. This research has produced significant original contributions in four areas: Building Information Modeling (BIM), the theory of formal language and formal studies in architecture, architectural design education and the role of BIM in design studios, and conducting research through design.

A Nonhomogeneous Bulk Flow Model for Prediction of the Static and Dynamic Forced Performance of Two Phase Flow Annular Seals

Lu, Xueliang Texas A&M University ProQuest Dissertations & Thes 2020 해외박사(DDOD)

In the subsea oil and gas industry, multiphase pumps and wet gas compressors are preferred technologies as they eliminate a conventional liquid-gas separation station to save up to 30% of capital investment. Seals in multiple phase pumps must be able to operate without compromising the system efficiency and its rotordynamic stability. However, both field operation and laboratory tests show that seals operating with liquid-gas mixtures could cause rotordynamic instability issues in a turbomachinery.This dissertation advances a nonhomogeneous bulk flow model (NHBFM) for the prediction of the leakage and dynamic force coefficients of uniform clearance annular seals lubricated with gas in liquid mixtures. Compared to a homogeneous bulk flow model (HBFM) the NHBFM contains four diffusion coefficients in the inertia terms of the momentum equations, and a transport equation for the gas volume fraction (GVF).To validate the model, predictions on leakage and dynamic force coefficients are compared against published results for three test seals supplied with a two-phase flow mixture. Two seals with a supply pressure Ps = 44.8 bara and a discharge pressure Pa = 6.9 bara emulate operating conditions in a subsea multiphase pump. The seals have the same diameter D = 89.3 mm and length L = 57.8 mm (L/D = 0.65), but different radial clearances, i.e., c = 0.140 ± 0.005 mm and 0.163 ± 0.005 mm, respectively. The shaft speed is 7,500 rpm (surface speed = 35 m/s), and the seal inlet GVF increases from 0 to 0.1. The mixture consists of compressed air and a synthetic oil with a low viscosity 4.53 cp at 40ºC and density of 899 kg/m3. The flow Reynolds number is within the range of 870 to 1,100, representing a laminar flow.The third test seal operates in a very different operating condition with a low pressure (Ps = 2.6 bara, Pa = 1 bara) and low shaft speed 3,500 rpm (surface speed = 23.3 m/s). The flow is an air in ISO VG10 mineral oil mixture with an inlet GVF spans 0 to 0.2. The maximum flow Reynolds number is less than 300. Thus, the flow is in laminar flow regime. The small pressure drop ΔP = 1.6 bar emulates operating conditions of impeller eye seals in electrical submersible pumps. The seal has a diameter D = 127 mm, length L = 46 mm (L/D = 0.36) and radial clearance c = 0.274 ± 0.005 mm.For the first test seal operating with Ps = 44.8 bara and inlet GVF=0.1, the flow is mostly homogeneous as the maximum diffusion velocity at the seal exit plane is just ~0.1% of the liquid flow velocity. Thus, both the NHBFM and HBFM predict similar results for the pressure field, gas volume fraction field, leakage (mass flow rate) and shear drag torque. The difference between the predicted leakage and test data is less than 5%.For operation with a Ps = 44.8 bara the NHBFM predicted direct stiffness (K) reduces faster with inlet GVF than that predicted by the HBFM. Although the NHBFM delivers 30% larger added mass (M) than the HBFM does, both models do predict a drop in M with the increase of inlet GVF. Both models predict similar direct damping coefficient (C) and cross-coupled stiffness (k) with a maximum difference of ~5% in both C and k for operation with inlet GVF= 0.1. Compared to the test data, the two models generally under predict C and k by the same amount of ~ 25%. Both C and k increase with inlet GVF for operation with inlet GVF < 0.1. Closely matching the test data, both models deliver a whirl frequency ratio (WFR) ~ 0.3 for the pure liquid seal. WFR increases to ~0.35 as the inlet GVF increases to 0.1.For the third test seal operating with a low pressure (Ps = 2.6 bara) both the NHBFM and HBFM predict ~ 0 direct stiffness (K). For operation with inlet GVF=0.2, the NHBFM predicted M is 3.2 kg, about ~30 % below the test data 4 kg; the HBFM predicts a zero M. C and k predicted by both models are within uncertainty of the test data. For operation with a pure liquid or a mixture both models deliver accurate predictions in whirl frequency ratio (WFR ~ 0.5).The comparisons of the predictions against test data from two-phase flow uniform clearance annular seals demonstrate that the NHBFM shows an improvement in prediction of the seals dynamic forced performance; in particular in direct stiffness (K), as compared to a HBFM. The difference in the predictions from the two models is primarily due to the distinct approaches to model the perturbed density of the two-phase flow, as is addressed later in the main context.In contrast to commercial computational fluid dynamics (CFD) software packages that require hours or even several days to obtain the dynamics force coefficients, the current NHBFM only takes one or two minutes to complete a prediction.

Structure-Based Drug Discovery Against Human Enl Yeats Domain and Sars-CoV-2 Main Protease

Ma, Xinyu Texas A&M University ProQuest Dissertations & Thes 2021 해외박사(DDOD)

Structure-based drug design is a drug discovery strategy where rational design of drug molecules take place based on the structural information of therapeutic targets. With the development of structural biology technologies such as protein crystallography and cryo-electron microscopy, which results in the availability of more and more proteins in a higher and higher resolution, structure-based drug design has become one of the most useful drug discovery strategy in both academia and pharmaceutical industry. This dissertation discusses applying structure-based drug design strategies in inhibitor development targeting ENL (eleven-nienteen leukemia) protein, which is an important protein in the mix lineage leukemia (MLL)-rearranged leukemia, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease, a vital viral enzyme for its replication.Chapter I is a brief introduction to the topics of this dissertation. Starting with a short introduction of the concept of structure-based drug design, it then mainly discusses the molecular mechanism of the pathogenesis and potential therapeutic targets of the following two diseases: MLL-rearranged leukemia and COVID-19.Chapter II describes the development of a series of selective ENL YEATS domain inhibitors. ENL is a histone acetylation reader essential for disease maintenance in acute leukemias, especially the MLL-rearranged leukemia. The function of ENL is dependent on the recognition of histone acetylation by its YEATS domain, suggesting that inhibition of the ENL YEATS domain is a potential strategy to treat MLL-rearranged leukemia. In our study, high-throughput screening of a small molecule library was carried out to identify inhibitors for the ENL YEATS domain. Structureactivity relationship studies of the hits and structure-based inhibitor design led to two compounds with IC50 values below 100 nM in inhibiting the ENL-acetyl-H3 interaction. Both compounds and their precursor displayed strong selectivity toward the ENL YEATS domain over all other human YEATS domains. One of these compounds also exhibited on-target inhibition of ENL in cultured leukemia cells and a synergistic effect with the BET bromodomain inhibitor JQ1 in killing leukemia cells. Together, we have developed selective inhibitors for the ENL YEATS domain, providing the basis for further medicinal chemistry-based optimization to advance both basic and translational research of ENL.Chapter III and IV describes the development of SARS-CoV-2 main protease inhibitors and the assessment of their selectivity against host proteases. The COVID-19 pathogen, SARS-CoV-2, requires its main protease (SC2Mpro) to digest two of its translated long polypeptides to form mature viral proteins that are essential for viral replication and pathogenesis. Inhibition of this vital proteolytic process is effective in preventing the virus from replicating in infected cells and therefore provides a potential COVID-19 treatment option. Guided by previous medicinal chemistry studies about SARS-CoV main protease (SC1Mpro), we designed and synthesized a series of peptidyl aldehyde inhibitors that reversibly covalently bind to the active cysteine of SC2Mpro. The most potent compound has an IC50 of 8.3 nM. Crystallographic analysis confirmed the covalent linkage between the aldehyde inhibitors and active cysteine and showed structural rearrangement of the apoenzyme to accommodate the inhibitors. Two inhibitors completely prevented the SARS-CoV-2-induced cytopathogenic effect in Vero E6 cells at 2.5–5 μM and A549/ACE2 cells at 0.16–0.31 μM.Even though a number of inhibitors have been developed for the SARS-CoV-2 main protease as potential COVID-19 medications, little is known about their selectivity. Using enzymatic assays, we characterized inhibition of TMPRSS2, furin, and cathepsin B/K/L by 11 previously developed Mpro inhibitors. Our data revealed that all these inhibitors are inert toward TMPRSS2 and furin. Diaryl esters also showed low inhibition of cathepsins. However, all aldehyde inhibitors displayed high potency in inhibiting three cathepsins. A cellular analysis indicated high potency of MPI5 and MPI8 in inhibiting lysosomal activity, which is probably attributed to their inhibition of cathepsins. Among all aldehyde inhibitors, MPI8 shows the best selectivity toward cathepsin L. With respect to cathepsin B and K. MPI8 is the most potent compound among all aldehyde inhibitors in inhibiting SARS-CoV-2 in Vero E6 cells. Cathepsin L has been demonstrated to play a critical role in the SARS-CoV-2 cell entry. By selectively inhibiting both SARS-CoV-2 MPro and the host cathepsin L, MPI8 potentiates dual inhibition effects to synergize its overall antiviral potency and efficacy. Due to its high selectivity toward cathepsin L that reduces potential toxicity toward host cells and high cellular and antiviral potency, we urge serious consideration of MPI8 for preclinical and clinical investigations for treating COVID-19.

Waveguide QED in the Squeezed Vacuum

You, Jieyu Texas A&M University ProQuest Dissertations & Thes 2020 해외박사(DDOD)

The well-known Purcell effect shows that the spontaneous decay rate of an emitter can be affected by the electromagnetic environment with which the emitters interact. One of the most famous and popular examples is the squeezed vacuum. Although the squeezed vacuum does not change the density of states of the electromagnetic modes, it can modify the decay rate as well as the dephasing rate of the emitters. The interaction between a single atom and the squeezed vacuum has been widely studied, while only a few publications deal with the multiple-atom system. Despite the fact that the dipole-dipole interaction induced by ordinary vacuum depends on the relative separation of atoms, there are only a few papers studying the impact of atomic separation in the squeezed vacuum. In this dissertation, we show that the interaction induced by the squeezed vacuum depends on the center of mass positions of the atoms, which is essentially different from that in the ordinary vacuum. We also illustrate how to choose the coordinate system to make the center of mass position reasonable and well-defined.Although the squeezed vacuum theory has been widely studied, it is impractical to generate a broadband squeezed vacuum reservoir which squeezes all modes in the 3-dimensional (3D) space. Recently, photon transport in a one-dimensional (1D) waveguide coupled to quantum emitters (well known as "waveguide-QED") has attracted much attention due to its possible applications in quantum device and quantum information. In contrast to the 3D case, squeezing in 1D is more experimentally feasible. Suppression of the spontaneous decay rate and the linewidth of the resonance fluorescence atom has been experimentally demonstrated in a 1D microwave transmission line coupled to a single artificial atom. However many-body interaction in a 1D waveguide QED system coupled to the squeezed vacuum has still not yet been studied. In this dissertation, we apply our theory to the 1D waveguide-QED system with the squeezed reservoir. Contrary to the traditional result that the dephasing rate of a single atom is a constant, our calculation shows that the dephasing rate is actually position-dependent. As the dipole-dipole interaction is involved in the atomic system, both the atomic separation and center of mass position have impacts on the decay rate, dephasing rate, and the emitted resonance fluorescence spectrum. Moreover, the stationary maximum entangled NOON state can be achieved if atomic transition frequency is resonant with the center frequency of the squeezed vacuum.In light of the fact that two qubits can be treated as a whole to be a four level atomic system, we also study the dynamics of Ξ-type atoms driven by a squeezed vacuum. We get the interesting result that the atomic system’s steady state is a pure state, and a complete population inversion can occur when the coupling between the atomic dipole and the squeezed vacuum satisfy some certain conditions. We also mathematically prove that the steady state of a many-body system is nothing else but the direct product of that in the single atom case even when dipole-dipole interaction is involved.

Three Essays on Applied Microeconomics

Mosquera Moyano, Roberto Texas A&M University ProQuest Dissertations & Thes 2019 해외박사(DDOD)

This dissertation presents three essays on the effects of different institutions, technologies, and shocks on health, education, labor and information outcomes using experimental and quasi-experimental research designs. Specifically, I consider the effects of social media, vaccination, and natural resources.In the first essay “The Economic Effects of Facebook”, joint work with Mofioluwasademi Odunowo, Trent McNamara, Xiongfei Guo, and Ragan Petrie, we study the effects of Facebook on news awareness, subjective well-being, and daily activities. We use a large field experiment with a validated Facebook restriction to document the value of Facebook to users and its causal effect on news consumption and awareness, well-being, and daily activities. Those who are off Facebook for a week reduce news consumption, are less likely to recognize politically-skewed news stories, report being less depressed and engage in healthier activities. One week of Facebook is worth $67, and this increases by 19.6 percent after experiencing a Facebook restriction.In the second essay “Vaccines at Work”, joint work with Manuel Hoffmann and Adrian Chadi, we study how behavioral factors can affect the effectiveness of flu vaccination. Flu vaccination could be a cost-effective way to handle the costs of this disease, but low takeup rates, particularly of working adults, and vaccination unintendingly causing moral hazard may decrease its benefits. We ran a natural field experiment with employees of a large bank in Ecuador where we experimentally manipulated incentives to participate in a flu vaccination campaign. We find that reducing the opportunity costs of vaccination increased take-up by 112 percent. Also, we find that the effect of vaccination on health outcomes is a precise zero with no measurable health externalities from coworkers. Using administrative records on sickness diagnoses and surveys, we find evidence consistent with vaccination causing moral hazard.In the third essay “A Blessing or a Curse? The Long-term Effect of Resource Booms on Human Capital and Living Conditions”, I study if resource booms can reduce human capital accumulation. These booms can increase the opportunity costs of education by favoring low-skill jobs, which makes it optimal for some cohorts to interrupt their education. If these individuals do not resume their education, they may lose pecuniary and non-pecuniary benefits of education in their lifetime. For a country, lower human capital may constrain its long-term growth. I use proprietary individual-level data to study the long-term effects of exposure to the 1970s oil boom on human capital in a developing country. I exploit variation in the timing of the shock and geographic differences in the cost of college attendance and find that exposure to the boom decreased college completion and increased low-skill occupations - consistent with the idea that individuals shift into highly remunerative low skilled employment because the boom decreased college education returns. In line with this, I find no effects on wealth accumulation.

Experiments and Predictions with a Foil Thrust Bearing supported by Metal Mesh Screen

Cable, Travis Alexander Texas A&M University ProQuest Dissertations & Thes 2020 해외박사(DDOD)

Modern micro-turbomachines (MTM) often employ light weight rotors operating at speeds in excess of 50 krpm. These turbomachines require radial and thrust bearings capable of handling high speeds, while also often operating in extreme environments (high and low temperature). Flexible structure air bearings, or foil bearings, provide an economical and clean (no oil or contamination) means of rotor support in this niche.To date, the most commonly utilized foil bearing is the bump-type foil bearing, which utilizes thin corrugated foil strips to support a smooth top foil on which hydrodynamic pressure builds. Despite its widespread use, each bump-foil is complex to build and model, requiring of extensive engineering knowledge and experience. As such, researchers continue to search for cheaper and less complex alternatives to the traditional bump-foil structure. Metal mesh, readily available and relatively cheap, is a viable option for radial foil bearings, but has yet to be investigated for use in foil thrust bearings.The dissertation presents the design and manufacture of a novel Rayleigh-step thrust foil bearing, whose top foil is supported by a circular layer (or layers) of compliant metal mesh screen. Static and dynamic load excitation tests (no rotor speed) with the prototype bearing reveal a structural stiffness which increases with the mass ratio of the mesh screen and decreases with the number of mesh layers used to support the top foil. Dynamic load excitation tests, up to 300 Hz., give a material loss factor γ ~ 0.2 for the mesh structure which is relatively unaffected by frequency. Foil bearings rely on structural damping from material hysteresis, and bump-type foil bearings exhibit a material loss factor which decreases quickly with an increasing excitation frequency, thus lending credence to metal mesh screen as a bearing support structure.Despite the promise of the novel Rayleigh-step foil thrust bearing, experiments with rotor speed failed several of the prototype top foils, the root-cause of which is attributed to the waviness of the metal mesh layers. This waviness unevenly bulges the thin top foil towards the spinning collar, causing solid contact between the metal top foil and collar before hydrodynamic pressure builds over the pads to separate the surfaces. The failure of several prototype foils points to the need of a robust coating for foil bearings, which can not be ignored by designers.Tests with a redesigned prototype, incorporating a circumferential taper and segmented pads, proved the bearing concept. A single pad bearing with a 55° arc extent and three layers of 40 OPI (openings per inch) mesh achieved a modest specific load of W/A = 35 kPa (per pad) at a rotor speed Ω = 40 krpm (ω·Rmid ~ 160 m/s). Further tests with a six-pad circumferentially tapered metal mesh foil thrust bearing (MMFTB) determined an ultimate load capacity of W/A ~ 25 kPa for Ω = 40 krpm. At this load capacity, the bearing temperature rise (measured via a thermocouple on the top foil backside) exceeded 110°C. The decreased load capacity for the six-pad bearing, as compared to the single-pad bearing, results from an uneven distribution of the thrust load between the six pads, as confirmed by temperature measurements on three of the top foil undersides. Similar to the Rayleigh-step top foil, the circumferentially tapered MMFTB suffered from taper height disparities between the pads, attributed to the waviness of the mesh, which is exacerbated by stacking multiple layers.In addition to the experimental work with compliant surface thrust bearings supported by metal mesh screen, the dissertation provides a thermo-elastohydrodynamic model, validated (to some degree) with cases from the literature. However, bearing drag torque measurements and predictions for a six-pad MMFTB do not agree well. A simple Couette-flow approximation for the bearing drag torque shows that the bearing would need to operate with a uniform film thickness (hconst = 2.7 μm) to produce the measured bearing drag torque (Texp = 180 N.mm). This minute film thickness is within typical combined roughness (rotor collar + pad roughness) values, and as such likely does not produce a full fluid film during operation. The simple analysis, along with posttest photographs of the thrust collar surface, corroborates the notion that the test bearing operated in the mixed-lubrication regime, with continuous sliding contact between asperities on the rotor collar and the pads coated with a sacrificial lubricant (MoS2).A further analysis with the current model compares the steady-state performance of a MMFTB with 3 sheets of 40 OPI mesh to that of a well-known BFTB geometry from the literature. Predictions show that the MMFTB has a nearly identical drag toque to that of the BFTB for loads 10 ≤ W/A ≤ 50 kPa and a large rotor speed Ω = 70 krpm (ω·Rmid ~ 279 m/s), although it has a slightly smaller film thickness (and likely a lower ultimate load capacity).Predictions with Ω = 70 krpm (ω·Rmid ~ 279 m/s) and a specific load W/A ≤ 30 kPa show that that the MMFTB operates slightly cooler than the BFTB (ΔTmax ~ 105 vs 115 K) when no cooling flow applies to the bearing. Applying cooling flow (0 ≤ Qcf ≤ 900 LPM) through the bearing center can decrease the peak film and top-foil temperatures by ~ 40°C, while decreasing the collar temperature by up to 10°C. For the bearing geometry utilized in the current predictions (see Table 14), a cooling flow rate Qcf ≥ 100 LPM fully supplies the pad leading edge, such that the bearing draws no fluid from the ambient air surrounding the bearing. Increasing the cooling flow beyond this point cools the pads via forced convection in the areas beneath the pad tapers (albeit little). For the MMFTB, the mesh screens under the pad and in the land section obstruct cooling flow, such that the cooling is less effective (when compared to the BFTB). Importantly, utilizing an aluminum collar (with a high thermal conductivity, κ = 130 W/m2K) limits the thermal gradient through the collar thickness to 5°C, reducing the possibility of thermal bending and a corresponding thermal runaway event.The dissertation adds to the archival literature on gas foil thrust bearings and provides a model for prediction of their performance. The failures detailed herein provide important lessons for foil bearing designers and researchers. Further research is needed to either qualify or disqualify metal mesh sheets as a viable underspring structure for gas foil thrust bearings, although the following document provides several cautions against their use.

A Thermo-Elasto-Hydrodynamic (Tehd) Computational Analysis for the Force Performance of Self-Equalizing Tilting Pad Thrust Bearings

Koosha, Rasool Texas A&M University ProQuest Dissertations & Thes 2020 해외박사(DDOD)

A self-equalizing tilting pad thrust bearing (TPTB) improves operation reliability by adjusting its pads to accommodate thrust collar tilt, and hence removing a source of frequent wearing. Although recent literature states the need, predictive models for self-equalizing TPTBs are not available due to the complexity of their geometry. To date published analyses limit to a few highly simplified analytical models. Nonetheless, a bearing manufacturer recently presented a complicated finite element model but excluded the fluid film analyses. The dissertation builds a thermo-elasto-hydrodynamic (TEHD) analysis tool and couples with a model for the pads leveling mechanism to deliver load performance predictions for self-equalizing TPTBs.The dissertation presents predictions for an example self-equalizing TPTB operating with a 0.01 thrust collar static misalignment and which equals to 75% of the nominal minimum film thickness when the bearing operates under 2 MPa/pad load and with a perfectly aligned thrust collar. The bearing has six pads with 63 mm in inner diameter (ID) and 126 mm in outer diameter (OD), operates at 4krpm (maximum surface speed = 26 m/s) and under a specific load/pad ranging from 0.5 to 3.5 MPa. Compared to a regular (non-equalizing) TPTB, a self-equalizing TPTB operates with up to 50% larger minimum film thickness and a roughly 1/2 of peak elastic deformation. Friction forces acting at the contact points of the leveling plates show a significant effect on the performance of the pad leveling system as they reduce the film clearance and increase a pad peak pressure. Predictions show a significantly large peak pressure at the contact points of the leveling plates (> 0.9 GPa) when the bearings operate under a 3 MPa/pad specific load. The present work thus shows the importance of performing a comprehensive multiple-pad analysis to accurately evaluate the performance of self-equalizing TPTBs hence assuring their safe operation.This dissertation further implements a flow starvation model into the TEHD computational analysis tool to deliver load performance predictions for TPTB operating with reduced flow rate. The work builds a model for the groove flow thermal mixing that determines the temperature of the lubricant entering a thrust pad for bearings operating with either reduced or over-flooded flow conditions. Unlike the hot oil carry-over model, the present model accounts for the churning oil in bearings with end-seals configuration. Under a starved flow condition, the analysis iteratively reduces the effective arc length of a wetted pad until matching the available flow.The analysis considers an example TPTB with ID= 122 mm and OD=267 mm, 38° pad arc length, operating at 4 krpm and 10 krpm (maximum surface speed ROΩ = 54-135 m/s), and under a specific load per pad from 0.7 MPa to 3.4 MPa. The bearing is supplied with 25% to 150% of the predicted nominal flow rate as well as with a flow rate recommended in the literature (~170% to 420% nominal).A supply flow rate above the nominal rate, increases the bearing drag torque but has little effect on the pad peak temperature rise or the pad minimum film thickness. A reduced flow, below the nominal rate, produces areas denuded of oil at both the pad leading edge and trailing edge, and thus the pad minimum film thickness substantially decreases while the film peak pressure largely increases. At 4 krpm and under a heavy load of 3 MPa/pad, the pad subsurface temperature rise almost doubles with a 30% nominal flow and exceeds the Babbitt critical temperature = 130°C. Also, compared to a flooded flow bearing, a starved flow bearing shows a larger axial stiffness coefficient but a much lesser axial damping coefficient. Despite a significant increase in the bearing drag torque, the recommended flow rate does not lead to either a notable increase in the minimum film thickness nor to a decrease in the maximum pad temperature rise.At a high rotor speed of 10 krpm, the example TPTB with a flooded configuration (with end-seals) operates with up to 11 μm lesser minimum film thickness, a 10°C larger pad maximum temperature rise, and a 11% larger bearing axial stiffness compared to those in an identical bearing but with evacuated configuration (without end-seals). The bearing ends configuration, however, shows marginal influence on the bearing performance at a low speed of 4 krpm.In sum, the dissertation introduces simple and effective models to deliver load performance predictions for self-equalizing TPTBs and TPTBs supplied with reduced flow rates. In particular, the dissertation advances the state-of-the-art by pioneering a computational analysis model for self-equalizing TPTBs and produces unique knowledge on their load performance characteristics.

Prediction Games: Encouraging Engagement with Data

Dzodom, Gabriel Serge Texas A&M University ProQuest Dissertations & Thes 2020 해외박사(DDOD)

Prediction games, data-driven games modeled after fantasy sports, are aimed to motivate people to explore, analyze, and develop their own understanding of large data sets. They revolve around activities where players examine historical data and information resources to make predictions about future events. As a result, they may help improve the players’ domain knowledge and data interpretation skills. But what matters in the design of such games? And, as we envision prediction games created by instructors in an educational environment, what forms of support aid the authoring of prediction activities yet involve very little to no programming? To answer these questions, we first conducted a survey of fantasy sports players which showed that many seek out information including news and data. They analyze this content to make predictions, resulting in them learning more about the sport. Next, we developed Fantasy Forecaster, a prediction game prototype to gather system requirements and user feedback. Lessons from the survey and development of the prototype informed our prediction games framework and its implementation in the climate domain: Fantasy Climate.Fantasy Climate is a prediction game based on weather data where players select a location among a set of choices based on whether their assessment of upcoming weather. In particular, they are asked to select which location will be warmest and coolest compared to their historic norms on an upcoming date. The game also featured communication tools, integrated climate-related news, and historical weather data with visualizations to make sense of them. User studies of Fantasy Climate revealed that social interaction, particularly asynchronous discussions made the game more engaging and helped players gather information for prediction making. Also, the in-game presentation of domain-related news had an effect on engagement and players' performance.From our prediction games framework and the implementation of Fantasy Climate, we identified a set of necessary and valuable prediction activity specifications which led to the development of the Activity Creation Wizard (ACW). The ACW is an environment that guides the author through a series of steps to author their prediction activity. Features of the ACW included a help system that provides the author with explanations, tutorials and examples during the authoring process. Also included were a template component that allows the author to reuse the customizations of a previously created prediction activity, and tools to automate repetitive and tedious tasks such as building the prediction schedule.The evaluation of the ACW showed no background knowledge was required to use the ACW to author a prediction activity. The help system was in general adequate in assisting the participants in their information needs, templates were found useful by many, and automation reduced the time taken for repetitive tasks. Some authors did not want to use templates or automation in order to have more control over the design of their activity. However, the help system, templates, and automation tools of the ACW were not sufficient in helping the participants understand the consequences of their customization on the prediction activity. Reasoning about the effects of their choices on gameplay was noted as the primary challenge during the authoring task by several participants. Additionally, the evaluation identified alternative ways of authoring the prediction activity that challenged our current design of the ACW, including the potential value of co-dependent customizations and collaborative authoring.Finally, the ACW evaluation also involved a task where participants created a prediction game in the domain of their choice. Interviews with participants on their created prediction games revealed two major findings. One finding was that educational, social, and socio-cultural factors play an important role in what makes prediction games engaging. The other finding was authoring resulted in a recognition by the participants of the educational benefits of prediction games which align well with the primary motives of this research work.

Development of a Processing Aid Containing Sodium Lactate, Sodium Erythorbate and Sodium Bicarbonate Applied to Beef Trimmings to Assess Their Impact on Quality of Ground Beef Patties

Wu, Chi-Heng Texas A&M University ProQuest Dissertations & Thes 2019 해외박사(DDOD)

A significant portion of fresh beef trimmings are distributed aerobically under refrigeration from large beef fabrication plants to further processors to use as the raw material source for products such as beef patties. Time from fabrication to arrival at further processing facilities may be anywhere from 0 to 5 days, or longer due to inclement weather conditions. This variation impacts the overall condition (color, odor/flavor/spoilage) of these trimmings destined for further processing, i.e, beef patty manufacture. The economic loss due to meat discoloration was estimated to be 1 billion/year. Most researches utilized single ingredient to address a specific problem, such as myoglobin oxidation, lipid peroxidation, etc. Hence, we proposed to develop a processing aid containing multiple selected ingredients to resolve the myoglobin oxidation, lipid peroxidation, off odor, and microbial spoilage which reduce the shelf life of aerobically stored beef trimmings. Phase 1 and 2 were conducted to investigate the effect of sodium lactate (NaL), potassium lactate (KL), sodium erythorbate (NaE), and sodium bicarbonate (NaB) on fresh beef trimmings for ground beef production within and exceeding federal regulations. For phase 1 and 2, a full factorial design was used to generate treatment combinations containing NaL (0.1 to 1.5 M), NaE (1 mM to 0.6 M), and NaB (0.1 to 1.5 M) with water used as a control in both studies. Based on phase 1 and 2, a 23 central composite response surface design (RSM), which generated 15 treatment combinations containing NaL (0.1 to 1.5 M), NaE (0.1 to 0.6 M), and NaB (0.1 to 1.5 M) with water used as a control was used to optimize the concentration level of treatment combinations. All phases used the same the procedure for treatment preparation, sample preparation, treatment application, sample collection and analysis. Beef trimmings fabricated from 14-day-postmortem carcasses were aerobically stored for 6 days at 5 °C. After storage, beef trimmings were coarse ground, treated with various treatments, reground, and formed into beef patties wrapped with oxygen permeable films. The patties were stored under simulated retail conditions: 5°C, cool white fluorescent light (200 to 300 lux) and analyzed at day 0, 3, 6, and 9 of storage to assess the effectiveness of each treatment in preventing further quality deterioration. Objective color (L*, a*, and b*), 2- thiobarbituric acid (TBA) determinations, GC-MS for off-odor assessment and aerobic plate counts (APC) were measured. The treated beef patties with NaB (1.5 M), NaE (0.1 to 0.8 M) and NaL (1 M) had the greatest effect on enhancing the color stability, reducing the lipid peroxidation and controlling the microbial spoilage compared to the control upon storage day 6 for phase 1 and 2, respectively. Based on these results, we optimized the concentration levels of NaL, NaE, and NaB which were active ingredients using response surface methodology (RSM) to develop a processing aid. The treated beef patties showed improved a* values, MMb formations, TBA values and total ion counts of hexanal compared to the control upon storage day 6 (P < 0.05). Based on the results, a* and TBA values were used to conduct multivariate RSM analyses for day 3 and 6. The predicted value of hexanal was 0 for all treatments. Multivariate RSM was conducted to overlap the contour plots of predicted a* and TBA values at day 3 and 6 to better approximate the optimal ingredient concentrations for a* values. The optimum concentration ranges of solutions based on this analysis were NaL (0.43 to 0.57 M), NaE (0.35 M) and NaB (1 M) with predicted a* values > 11 and TBA values < 0.52. Results of the research suggested that a combination of NaL, NaE and NaB (0.43 to 0.57, 0.35 and 1 M, respectively) could be applied into ground beef patties generated from aerobically 6-days-stored (5 °C) beef trimmings to improve color stability, reduce lipid oxidation and mitigate off-odor upon 6 days storage with retail display condition.

Measurement of self-efficacy, predisposition for collaboration, and project scores in architectural design studios

Luhan, Gregory Anthony Texas A&M University ProQuest Dissertations & Thes 2016 해외박사(DDOD)

The design of high-performance, sustainable, built environments in architectural practice is becoming more collaborative, and the demands on architectural education to provide measurable learning outcomes that more successfully prepare students to contribute in a practice setting are increasing. Since educational experts assert that self-efficacy is a key attribute of successful students and architectural education relies heavily upon project-based learning in design studios, it is a reasonable expectation that the character and quality of architectural design studio courses may affect the development of Design Self-Efficacy. This research has developed instruments by which instructional methods, self-efficacy, and student projects may be measured and scored, enabling reliable and valid investigation of the relationships among these factors. This dissertation has three primary foci: (1) developing an instrument to measure student Design Self-Efficacy and predisposition to collaboration in design studios; (2) developing a framework for better understanding how studio type and project type impact Design Self-Efficacy, and (3) developing an instrument employing an assessment rubric to measure student learning outcomes through end results of a Project Score. Data was collected from Texas A&M University, the University of Kentucky, and the University of Kansas via content analysis of studio syllabi; focus groups and interviews with faculty; electronic surveys of students enrolled in architectural design studios; and the assessment of projects using a validated rubric. This research included the development and calibration of measurement instruments to determine if correlation exists between Design Self-Efficacy (DSE), disposition for collaboration (PD), studio-type (ST), project-type (PT), and project score (PS). Research revealed that PD is sensitive to different students and different moments in time. The DSE instrument produced results that aligned to self-efficacy theory and data analysis revealed increased self-efficacy from undergraduate through graduate studies, and theoretical groupings that parallel the processes of design studio problem solving, project development, iteration, evaluation, and communication. The PS data analysis revealed gaps in architectural design studio evaluations that can be addressed with an assessment rubric. The results of this dissertation serve as a foundation for a future research agenda to improve design education, inform the accreditation process of professional architecture programs in North America and by extension, impact the practice of architecture.