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- Creators: Arizona State University
Description
In 1946 Felix Bloch first demonstrated the phenomenon of nuclear magnetic resonance using continuous-wave signal generation and acquisition. Shortly after in 1966, Richard R. Ernst demonstrated the breakthrough that nuclear magnetic resonance needed to develop into magnetic resonance imaging: the application of Fourier transforms for sensitive pulsed imaging. Upon this discovery, the world of research began to develop high power radio amplifiers and fast radio switches for pulsed experimentation. Consequently, continuous-wave imaging placed on the backburner.Although high power pulses are dominant in clinical imaging, there are unique advantages to low power, continuous-wave pulse sequences that transmit and receive signals simultaneously. Primarily, tissues or materials with short T2 time constants can be imaged and the peak radio power required is drastically reduced.
The fundamental problem with this lies in its nature; the transmitter leaks a strong leakage signal into the receiver, thus saturating the receiver and the intended nuclear magnetic resonance signal is lost noise.
Demonstrated in this dissertation is a multichannel standalone simultaneous transmit and receive (STAR) system with remote user-control that enables continuous- wave full-duplex imaging. STAR calibrates cancellation signals through vector modulators that match the leakage signal of each receiver in amplitude but opposite in phase, therefore destructively interfering the leakage signals. STAR does not require specific imaging coils or console inputs for calibration. It was designed to be general- purpose, therefore integrating into any imaging system. To begin, the user uses an Android tablet to tune STAR to match the Larmor frequency in the bore. Then, the user tells STAR to begin calibration. After self-calibrating, the user may fine-tune the calibration state of the system before enabling a low-power mode for system electronics and imaging may commence. STAR was demonstrated to isolate two receiver coils upwards of 70 dB from the transmit coil and is readily upgradable to enable the use of four receive coils.
Some primary concerns of STAR are the removal of transceivers for multichannel operation, digital circuit noise, external noise, calibration speed, upgradability, and the isolation introduced; all of which are addressed in the proceeding thesis.
ContributorsColwell, Zachary Allen (Author) / Sohn, Sung-Min (Thesis advisor) / Trichopoulos, Georgios (Thesis advisor) / Aberle, James (Committee member) / Sadleir, Rosalind (Committee member) / Arizona State University (Publisher)
Created2023
Description
This thesis is developed in the context of biomanufacturing of modern products that have the following properties: require short design to manufacturing time, they have high variability due to a high desired level of patient personalization, and, as a result, may be manufactured in low volumes. This area at the intersection of therapeutics and biomanufacturing has become increasingly important: (i) a huge push toward the design of new RNA nanoparticles has revolutionized the science of vaccines due to the COVID-19 pandemic; (ii) while the technology to produce personalized cancer medications is available, efficient design and operation of manufacturing systems is not yet agreed upon. In this work, the focus is on operations research methodologies that can support faster design of novel products, specifically RNA; and methods for the enabling of personalization in biomanufacturing, and will specifically look at the problem of cancer therapy manufacturing. Across both areas, methods are presented attempting to embed pre-existing knowledge (e.g., constraints characterizing good molecules, comparison between structures) as well as learn problem structure (e.g., the landscape of the rewards function while synthesizing the control for a single use bioreactor). This thesis produced three key outcomes: (i) ExpertRNA for the prediction of the structure of an RNA molecule given a sequence. RNA structure is fundamental in determining its function. Therefore, having efficient tools for such prediction can make all the difference for a scientist trying to understand optimal molecule configuration. For the first time, the algorithm allows expert evaluation in the loop to judge the partial predictions that the tool produces; (ii) BioMAN, a discrete event simulation tool for the study of single-use biomanufacturing of personalized cancer therapies. The discrete event simulation engine was designed tailored to handle the efficient scheduling of many parallel events which is cause by the presence of single use resources. This is the first simulator of this type for individual therapies; (iii) Part-MCTS, a novel sequential decision-making algorithm to support the control of single use systems. This tool integrates for the first-time simulation, monte-carlo tree search and optimal computing budget allocation for managing the computational effort.
ContributorsLiu, Menghan (Author) / Pedrielli, Giulia (Thesis advisor) / Bertsekas, Dimitri (Committee member) / Pan, Rong (Committee member) / Sulc, Petr (Committee member) / Wu, Teresa (Committee member) / Arizona State University (Publisher)
Created2023
Description
Obesity has consistently presented a significant challenge, with excess body fat contributing to the development of numerous severe conditions such as diabetes, cardiovascular disease, cancer, and various musculoskeletal disorders. In this study, different methods are proposed to study substrate utilization (carbohydrates, proteins, and fats) in the human body and validate the biomarkers enabling to investigation of weight management and monitor metabolic health. The first technique to study was Indirect calorimetry, which assessed Resting Energy Expenditure (REE) and measured parameters like oxygen consumption (VO2) and carbon dioxide production (VCO2). A validation study was conducted to study the effectiveness of the medical device Breezing Med determining REE, VO2, and VCO2. The results were compared with correlation slopes and regression coefficients close to 1. Indirect Calorimetry can be used to determine carbohydrate and fat utilization but it requires additional correction for protein utilization. Protein utilization can be studied by analyzing urinary nitrogen. Therefore, a secondary technique was studied for identifying urea and ammonia concentration in human urine samples. Along this line two methods for detecting urea were explored, a colorimetric technique and it was validated against the Ion-Selective method. The results were then compared by correlation analysis of urine samples measured with both methods simultaneously curves. The equations for fat, carb, and protein oxidation, involving VO2, VCO2 consumption, and urinary nitrogen were implemented and validated, using the above-described methods in a human subject study with 16 subjects. The measurements included diverse diets (normal vs. high fat/protein) in normal energy balance and pre-/post interventions of exercise, fasting, and a high-fat meal. It can be concluded that the indirect calorimetry portable method in conjunction with urine urea methods are important to help the understanding of substrate utilization in human subjects, and therefore, excellent tools to contribute to the treatments and interventions of obesity and overweighted populations.
ContributorsPradhan, Ayushi (Author) / Forzani, Erica (Thesis advisor) / Lind, Mary Laura (Committee member) / Wang, Shaopeng (Committee member) / Arizona State University (Publisher)
Created2023
Description
A key contribution of human factors engineering is the concept of workload: a construct that represents the relationship between an operator’s cognitive resources, the demands of their task, and performance. Understanding workload can lead to improvements in safety and performance for people working in critical environments, particularly within action teams. Recently, there has been interest in considering how the workload of a team as a whole may differ from that of an individual, prompting investigation into team workload as a distinct team-level construct. In empirical research, team-level workload is often considered as the sum or average of individual team members' workloads. However, the intrinsic characteristics of action teams—such as interdependence and heterogeneity—challenge this assumption, and traditional methods of measuring team workload might be unsuitable. This dissertation delves into this issue with a review of empirical work in action teams, pinpointing several gaps. Next, the development of a testbed is described and used to address two pressing gaps regarding the impact of interdependence and how team communications relate to team workload states and performance. An experiment was conducted with forty 3-person teams collaborating in an action team task. Results of this experiment suggest that the traditional way of measuring workload in action teams via subjective questionnaires averaged at the team level has some major shortcomings, particularly when demands are elevated, and action teams are highly interdependent. The results also suggested that several communication measures are associated with increases in demands, laying the groundwork for team-level communication-based measures of team workload. The results are synthesized with findings from the literature to provide a way forward for conceptualizing and measuring team workload in action teams.
ContributorsJohnson, Craig Jonathon (Author) / Cooke, Nancy J (Thesis advisor) / Gutzwiller, Robert S (Committee member) / Holder, Eric (Committee member) / Amazeen, Polemnia G (Committee member) / Arizona State University (Publisher)
Created2023
Description
In this dissertation, the nanofabrication process is characterized for fabrication of nanostructure on surface of silicon and gallium phosphide using silica nanosphere lithography (SNL) and metal assisted chemical etching (MACE) process. The SNL process allows fast process time and well defined silica nanosphere monolayer by spin-coating process after mixing N,N-dimethyl-formamide (DMF) solvent. The MACE process achieves the high aspect ratio structure fabrication using the reaction between metal and wet chemical. The nanostructures are fabricated on Si surface for enhanced light management, but, without proper surface passivation those gains hardly impact the performance of the solar cell. The surface passivation of nanostructures is challenging, not only due to larger surface areas and aspect ratios, but also has a direct result of the nanofabrication processes. In this research, the surface passivation of silicon nanostructures is improved by modifying the silica nanosphere lithography (SNL) and the metal assisted chemical etching (MACE) processes, frequently used to fabricate nanostructures. The implementation of a protective silicon oxide layer is proposed prior to the lithography process to mitigate the impact of the plasma etching during the SNL. Additionally, several adhesion layers are studied, chromium (Cr), nickel (Ni) and titanium (Ti) with gold (Au), used in the MACE process. The metal contamination is one of main damage and Ti makes the mitigation of metal contamination. Finally, a new chemical etching step is introduced, using potassium hydroxide at room temperature, to smooth the surface of the nanostructures after the MACE process. This chemical treatment allows to improve passivation by surface area control and removing surface defects. In this research, I demonstrate the Aluminum Oxide (Al2O3) passivation on nanostructure using atomic layer deposition (ALD) process. 10nm of Al2O3 layer makes effective passivation on nanostructure with optimized post annealing in forming gas (N2/H2) environment. However, 10nm thickness is not suitable for hetero structure because of carrier transportation. For carrier transportation, ultrathin Al2O3 (≤ 1nm) layer is used for passivation, but effective passivation is not achieved because of insufficient hydrogen contents. This issue is solved to use additional ultrathin SiO2 (1nm) below Al2O3 layer and hydrogenation from doped a-Si:H.
Moreover, the nanostructure is creased on gallium phosphide (GaP) by SNL and MACE process. The fabrication process is modified by control of metal layer and MACE solution.
ContributorsKim, Sangpyeong (Author) / Honsberg, Christiana (Thesis advisor) / Bowden, Stuart (Committee member) / Goryll, Michael (Committee member) / Augusto, Andre (Committee member) / Arizona State University (Publisher)
Created2021
Description
The world faces significant environmental and social challenges due to high economic development, population growth, industrialization, rapid urbanization, and unsustainable consumption. Global communities are taking the necessary measures to confront these international challenges and applying sustainable development principles across all sectors. Construction is a critical driving instrument of economic activity, and to achieve sustainable development, it is vital to transform conventional construction into a more sustainable model. The research investigated sustainable construction perceptions in Kuwait, a rapidly growing country with a high volume of construction activities. Kuwait has ambitious plans to transition into a more sustainable economic development model, and the construction industry needs to align with these plans. This research aims to identify the characteristics of sustainable construction applications in the Kuwaiti construction market, such as awareness, current perceptions, drivers and barriers, and the construction regulations' impact. The research utilized a qualitative approach to answer research questions and deliver research objectives by conducting eleven Semi-structured interviews with experienced professionals in the Kuwaiti construction market to collect rich data that reflects insights and understandings of the Kuwaiti construction industry. The Thematic analysis of the data resulted in six themes and one sub-theme that presented reflections, insights, and perspectives on sustainable construction perceptions in the Kuwaiti construction market. The research findings reflected poor sustainable construction awareness and poor environmental and social application in the construction industry, the determinant role of construction regulations in promoting sustainable construction. and barriers and drivers to sustainable construction applications. The research concluded with answers to research questions, delivery of research objectives, and an explanation of sustainable construction perceptions in the Kuwaiti construction market.
Contributorsalsalem, mohammad salem (Author) / Duran, Melanie (Thesis advisor) / Chong, Oswald (Committee member) / Sullivan, Kenneth (Committee member) / Grau, David (Committee member) / Arizona State University (Publisher)
Created2023
Description
Delamination of solar module interfaces often occurs in field-tested solar modules after decades of service due to environmental stressors such as humidity. In the presence of water, the interfaces between the encapsulant and the cell, glass, and backsheet all experience losses of adhesion, exposing the module to accelerated degradation. Understanding the relation between interfacial adhesion and water content inside photovoltaic modules can help mitigate detrimental power losses. Water content measurements via water reflectometry detection combined with 180° peel tests were used to study adhesion of module materials exposed to damp heat and dry heat conditions. The effect of temperature, cumulative water dose, and water content on interfacial adhesion between ethylene vinyl acetate and (1) glass, (2) front of the cell, and (3) backsheet was studied. Temperature and time decreased adhesion at all these interfaces. Water content in the sample during the measurement showed significant decreases in adhesion for the Backsheet/Ethylene vinyl acetate interface. Water dose showed little effect for the Glass/ Ethylene vinyl acetate and Backsheet/ Ethylene vinyl acetate interfaces, but there was significant adhesion loss with water dose at the front cell busbar/encapsulant interface. Initial tensile test results to monitor the effects of the mechanical properties ethylene vinyl acetate and backsheet showed water content increasing the strength of ethylene vinyl acetate during plastic deformation but no change in the strength of the backsheet properties. This mechanical property change is likely inducing variation along the peel interface to possibly convolute the adhesion measurements conducted or to explain the variation seen for the water saturated and dried peel test sample types.
ContributorsTheut, Nicholas (Author) / Bertoni, Mariana (Thesis advisor) / Holman, Zachary (Committee member) / Chan, Candace (Committee member) / Arizona State University (Publisher)
Created2020