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Design & Manufacture of Additive Manufactured Polymer-Metal Interfaces
No full textThis research investigates the design and manufacture of additively manufactured polymer-metal interfaces while correlating their processing, structure, properties, and performance (PSPP). Our primary goal is to tailor interface design and manufacture to effectively withstand tensile, shear, and combined loading, while fulfilling the constraints of avoiding adhesives or fasteners between the components. To achieve this goal, this study employs mechanical interlocking between polymer and metal surfaces (at a specific size-scale) that includes repeated geometry features (unit-cells) additively manufactured onto the metal surface, and the polymer additively ���infilled��� onto them. The geometrical designs were tailored taking into consideration the advantages and limitations of ���PBF-LB��� for the metal printing (316L stainless-steel), and ���MEX-TRB��� for the polymer printing (PCABS). The study includes the evaluation of various factors affecting the interface ���quality���, including unit-cell shape/size/distribution designs and their implications for polymer filling vs. load capability, the effect of manufacturing process parameters on the interface, and their impact on stress distribution and eventually performance under various loading scenarios. FEA simulations were employed to tailor designs and to parametrically predict the stress-based performance of the interfaces; insights into stress distributions, load capacity and critical points were obtained. Finally, candidate interface designs were additively manufactured, and their performance analyzed under various loading conditions. Altogether, this research strives to facilitate the use of polymer-metal interfaces within additive manufactured components
Isla Piedra: Coastal Shoreline Change of an Ancient Human Settlement on the Gulf of Mexico
No full textAlong the Gulf of Mexico, on the northwest corner of the Yucat��n Peninsula, sits the northern coastal plain of the State of Campeche. The shoreline of this plain is impacted by coastal processes and ecological succession based on low-energy waves that transport and deposit sediment. These processes form a muddy shoreline with extensive wetlands, characterized by estuaries, mangrove forests, floodplains (ci��nagas) and islands of vegetation known as hardwood hammocks (petenes). This dynamic ecological frontier is a transition zone between marine and terrestrial environments, perpetually undergoing change. Ancient human settlements of varying levels of complexity have been documented along this shoreline, all of which were subject to dynamic coastal processes���such as the case of Isla Piedra. However, there has been limited exploration into whether these dynamics have modified the landscape of these settlements over time. This research seeks to determine if the ancient inhabitants of Isla Piedra experienced a different coastal landscape compared to today and how this influenced their adaptive behaviors. First, the relationship between coastal geomorphology and ancient human settlements is established. Then, through change detection methods, a series of remote sensing satellite images of the coastline are analyzed to identify differences indicative of landscape changes. Based on the detected alterations, this research proposes potential shoreline changes that Isla Piedra inhabitants may have experienced during its primary period of ancient occupation. This change provides a foundation for future research about site formation and adaptive strategies developed by the island���s inhabitants
Effect of Overnight Storage Conditions on Dimensional Stability of Conventional Injection Molded, 3D Printed and Milled Complete Dentures
No full textStatement of problem: In modern prosthodontics the fabrication method of complete dentures has become more diverse than ever with the introduction of 3D printing and milling manufacturing. Despite the variety of manufacturing methods developed, the storage recommendations have remained virtually unchanged and untested for new manufacturing methods. Water storage has traditionally been advised at nighttime to prevent denture base distortion through the loss of moisture in the acrylic resin matrix. With the advent of CAD/CAM 3D printed denture bases and Milled denture bases from solid pucks of preprocessed acrylic the necessity to store dentures in liquid when not in use to the authors knowledge has remained untested.
Purpose: The aim of this study was to evaluate whether there is any typical deformation pattern of Injection molded, 3D printed and milled complete dentures stored in different overnight storage conditions for 14 days.
Materials & Methods: One edentulous maxillary typodont model was used as reference for fabrication of n=60 samples of identical digitally designed denture bases. Each denture base was approximately 2 mm thick and n= 20 samples were fabricated from each respective material; Ivobase injection molded pink hybrid denture base resin, Sprintray denture base EU 3D printed resin and Avadent Milled denture bases PMMA Puck LIGHT ��� Universal Shoulder. n=10 samples from each material group were randomly assigned to either a wet or dry storage group. All denture bases were submerged in 37 ��C Water bath for 12 hrs. and alternated for 14 days between their respective storage conditions and heated water bath simulating the oral cavity. Samples were scanned at 3-time intervals time ���0��� (T0), on the 7th day (T1), on the 14th day (T2). Scans were measured for deviations from the reference scan. Statistical analysis performed using Kruskal-Wallis with Bonferroni corrections (����=0.05) for between group differences and Related Samples Friedmans Two-way analysis of variance by ranks for within group differences.
Results: The Group 2 denture bases fabricated from the Ivobase and placed in the dry storage conditions demonstrated greater dimensional change with statistically significant differences in RMS value compared to the Group 1 Ivobase wet storage conditions (p< 0.003). In addition, the Group 3 & 4 Sprintray (wet/dry) demonstrated lower RMS values (p<0.007 & p<0.015) and better stability over time compared to the Group 2 Ivobase dry storage at time points T0-T2. The Avadent milled dentures demonstrated greater RMS value and distortion than the Group 1 Ivobase wet (p<.001), Group 3 Sprint ray wet (p<.001) and Group 4 Sprintray dry (p<.001). There was no significant difference in RMS value between the dry storage and wet storage of the Avadent denture bases.
Conclusions: Statistically greater dimensional changes were found in the dry storage group of Ivobase denture bases compared to the wet denture bases. Sprintray 3D printed denture bases exhibited no statistically significant dimensional changes in 14 days when stored in wet or dry conditions. Avadent milled denture bases exhibited no statistically significant dimensional changes in 14 days when stored in wet or dry conditions, but experienced greater dimensional change compared to Ivobase wet and Sprintray wet/dry storage conditions. All groups regardless of timepoint or storage conditions experience dimensional changes less than <1mm
Multi-Cycle Dynamic Compaction of At-Speed Tests for Reduction in Test Data Volume, Test Application Time, and Power Supply Noise
No full textThe semiconductor industry has made great strides over the last few decades. Chip makers taking advantage of Moore���s law have pushed the limits of physics to shrink feature sizes on Silicon (Si) wafers. Delay test is an essential structural manufacturing test used to determine the maximal frequency at which the chip can run without incurring any functional failures. Small delay defects that were previously benign now manifest as delay faults due to the reduced timing margins. Another challenge is achieving better delay correlation with functional test, which is dominated by power supply noise (PSN). Differences in PSN between functional and structural tests can lead to differences in chip operating frequencies of 30% or more. Pseudo functional test (PFT), based on a multicycle clocking scheme, has better PSN correlation with functional test compared with traditional two-cycle at-speed test. This research focuses on the development of new test. methods for small delay defects, within the limits of affordable test generation cost, pattern count and power supply noise.
First, this work proposes a new Dynamic Compaction algorithm to generate compacted test sets for K Longest paths per gate (KLPG) in scan based sequential circuits. The algorithm uses a greedy approach to compact paths with non-conflicting assignments together over multiple at-speed cycles during test generation. Reductions in pattern counts of as much as 67% are observed with the greedy approach.
Second, compression is introduced to the test flow and the ATPG engine to observe the combined effect of compression and compaction. Multi-cycle at-speed test has around 60% reduction in pattern count over single-cycle at-speed test with similar compression rates. Higher compression rates are required for single cycle test to achieve similar test data volume and test application time which indicates more DFT effort required for single cycle at-speed tests. The compression framework is built inside the CodGen ATPG to make this process more seamless.
Third, a simulation-based test relaxation algorithm is designed for CodGen ATPG as the patterns generated by the final justification SAT Engine assigns all the bits in the pattern. This algorithm implemented inside CodSim is able to produce similar don���t care bit density compared to the previous justification algorithms inside CodGen such as FAN and PODEM. Power supply noise (PSN) estimation using weighted switching activity (WSA) is then done for these partially specified patterns (with random or adjacent fill) to compare the single and multi-cycle test power. The multi-cycle test has very similar power profile and even lower in some cases to that of single-cycle test even though the patterns are more compacted.
Finally, CodGen ATPG is improved to handle larger industrial designs by updating the SAT engine MiniSat that runs all binary justifications during the ATPG process. It is replaced with CaDiCaL a much modern SAT engine which has been able to provide significant speedup to the test generation process
Sustainable Plastic Waste Recycling: Economics and Circularity Metrics
No full textOver the past few decades, the surge in plastic waste has created an urgent need for sustainable recycling methods to align with the Circular Economy (CE) goals. Process systems engineering (PSE) models have emerged as invaluable tools in plastic waste recycling, facilitating sustainability-driven problem-solving, optimizing process frameworks, and guiding the journey toward environmentally conscious circular solutions. This work proposes a robust mathematical model to optimize different recycling technologies, including pyrolysis, gasification, mechanical recycling, and incineration, striking a balance between economic feasibility and contribution to circular economy objectives. The model recognizes the potential of chemical recycling derivatives as versatile raw materials for various applications, including methanol synthesis, ammonia synthesis, hydrogen production, and more. It reveals the possibility of plastic waste yielding energy and valuable products through open- and closed-loop recycling pathways. A novel degree of circularity metric (DOCI) is enlisted to assess these pathways' contributions to the CE critically. It integrates various vital metrics, ensuring a holistic evaluation of each recycling route, encompassing material utilization, energy demand, water usage, waste generation, carbon footprint, economic viability, co-product utilization, recyclability, quality of the product, and technology maturity. An illustrative case study involving 20 scenarios for recycling plastic waste was evaluated and analyzed against incineration as a base case. The optimization results reveal that pyrolysis refinery technology offers promising avenues for producing sustainable fuels and olefins by tripling the base case profitability and more than 25% improvement in the total degree of circularity. Moreover, seeking the maximum possible circularity can be achieved by combining methanol synthesis and the pyrolysis refinery. This will provide an overall net profit of $29 M USD/y and a 44% enhancement of the DOCI of the base case. The flexible weight allocation for DOCI individual indicators in the optimization process emphasizes the significance of tailored solutions aligned with system-specific needs. Comparisons between plastic waste and conventional feedstocks are carried out, unveiling a product-dependent cost-effectiveness landscape. Capacity-level sensitivity analysis reveals that the optimal solutions consistently outperform the base case regarding circularity and profitability
Essays in Monetary Policy and Household Expectations
No full textThis dissertation focuses on the formation and implications of household beliefs and expectations with respect to monetary policy.
In the first chapter, I investigate whether consumer sentiment (analogously referred to as confidence) matters for monetary policy. Specifically, I consider whether consumer sentiment responds to monetary policy shocks, as well as whether the responses of output, inflation, and unemployment depend on the state of consumer sentiment. Although various methods of measuring confidence/sentiment exist, the underlying goal of each is to gauge how the normative economic attitudes of households change over time. As such, asking whether consumer sentiment responds to monetary policy shocks can alternatively be viewed as whether monetary policy shocks change households��� perceptions of the current/future state of the economy. Additionally, while some of the variation in sentiment reflects movement in aggregate fundamentals, a number of papers have established that the unaccounted for portion has predictive power for a variety of macroeconomic variables. This observation motivates considering whether the state of consumer sentiment suggests different macroeconomic impacts of monetary policy shocks.
Using an external identification scheme in a local projections (LP) approach, I find that contractionary monetary policy shocks have only minor negative effects on consumer sentiment. Consumer sentiment is measured by the headline index published by the Michigan Survey of Consumers. Further, I find that this minor response persists across various states of inflation, business cycles, and interest rates. In contrast, I do find evidence that the state of consumer sentiment matters for how output, inflation, and unemployment respond to these shocks. Specifically, positive interest rate shocks during periods of depressed consumer sentiment have quicker and more contractionary effects on output and unemployment, while inflation is not responsive over short nor long term horizons.
In the second chapter, I utilize a novel feature of the Michigan Survey of Consumers (MSC) to identify whether respondent expectations change within tight windows around macroeconomic data releases. This feature of the data is the interview dates of respondents between June 1979 ��� May 2019. Over this period, I include releases of the Employment Situation Summary (ESS), Consumer Price Index (CPI), Industrial Production (IP), and Gross Domestic Product (GDP), as well as Federal Open Market Committee (FOMC) meetings and calls. Incorporating the interview dates of each respondent alleviates a major identification problem that has prevented previous empirical work from using the MSC data to address such a question. Without them, one would only know which survey the person was interviewed for, but not when it was conducted. Thus, it was not possible to discriminate between the different information sets of the respondents, thereby preventing identification of the change in inflation expectations in response to a particular release.
My work in this paper furthers our understanding of household inflation expectations along a number of dimensions. First, I find that expectations significantly respond to information about the unemployment rate and CPI inflation, indicating that these are more salient to households than the other releases. I measure the information being conveyed by the releases by using the size and sign of changes in the release relative to the previous periods value. Second, I consider whether the relevance of these releases differs during recessions, the first paper to empirically address such a question. I find that information about the unemployment rate is particularly salient preceding, during, and following recessions. The final contribution I make in this paper is the finding that, over a shorter subsample, unanticipated changes in output growth prompt households to adjust their inflation expectations. Here, unanticipated refers to the difference between the realized value and Bloomberg consensus forecast value for each release, wherein inflation expectations respond to such deviations in IP and real GDP growth
Investigating Vaccinia Virus D10 and Its Homologs
No full textRNA decapping is a fundamental step in eukaryotic mRNA metabolism facilitating the regulation of gene expression by initiating mRNA decay or translational repression. Poxviruses and other nucleocytoplasmic large DNA viruses (NCLDV) encode mRNA decapping enzymes to modulate host and viral RNA levels during infection. The decapping activity is catalyzed by the nudix motif in the protein, which removes the 5��� end m7G cap structure of eukaryotic mRNA by hydrolysis. The prototype poxvirus, vaccinia virus (VACV), encodes two mRNA decapping enzymes: D9 and D10. Previous research has demonstrated the importance of these enzymes by showing a reduction in viral replication when the nudix motif is disabled by mutating key amino acids. Our lab recently showed that VACV D10 colocalizes with mitochondria and that colocalization is also required for VACV replication, hinting at important regulatory mechanisms for D10���s decapping function. Here, we characterized a recombinant VACV with both D9 and D10 knocked out (v���D9���D10). We compared the viral replication dynamics and plaque sizes between v���D9���D10 and the nudix mutant virus (vD9muD10mu). We found that v���D9���D10 showed a significant decrease in both plaque size and viral replication as compared to vD9muD10mu. This result suggests critical regulatory mechanisms of D9/D10 decapping activity that are required for efficient VACV replication. The v���D9���D10 recombinant virus was then used to investigate the ability of D10 homologs to compensate for the loss of D9 and D10. Our findings suggest that the ability of mRNA decapping enzymes to compensate for lack of D10 is unlikely to correlate to the overall sequence similarity, suggesting a more complex regulation mechanism of decapping enzyme���s functions. Additionally, investigation into structural homology led to the discovery that the mitochondrial localization motif recently identified in D10 is structurally conserved in many of the tested homologs. These findings also indicate the possibility that decapping enzymes homologous to D10 may also possess unique functions which aid in their effectiveness
Linking Cardiovascular and Neuromotor Responses to an Orthostatic Challenge
No full textHuman physiology has adapted few responses to changes in the orthostatic gradient typically caused by gravity and postural changes. Sustained alterations to our gravitational environment, whether through bedrest or during human spaceflight missions, are known to elicit multi-system physiological decrements. Previous work has identified potential differences in the responses of males and females.
The current work delivered an acute bout of orthostatic stress to 24 sex-balanced subjects via step-wise increases in lower-body negative pressure (LBNP) levels. During this intervention, subjects performed one of four bimanual coordination tasks. Measures of systemic hemodynamics, autonomic indices, and bimanual coordination task performance were performed. Orthostatic dose-response curves were generated, and a correlation analysis between the metrics of the two systems was performed. Additionally, statistical models were selected that best predict tolerance to the orthostatic challenge using baseline cardiovascular metrics. Models using cardiovascular metrics to best predict task performance were also selected.
The orthostatic challenge was successful in eliciting early and robust cardiovascular responses, especially in metrics related to sympathetic drive. Neuromotor performance changes to the orthostatic challenge, where they occurred, were usually only detectable in the final levels of the LBNP intervention. The most consistent neuromotor responses were increases in the pace of motor inputs, and increases in the variability of forces applied. Baseline cardiovascular health metrics were the best predictors of tolerance. Time-domain autonomic indices of heart rate variability were shown to be the strongest predictors of the increases in the pace of motor inputs. No differences were detected between male and female Index of Tolerance scores.
These results inform our understanding of cardiovascular and neuromotor responses to an orthostatic challenge both in a dose-response manner and an integrative manner. They suggest that neuromotor decrements may occur at the point during an orthostatic challenge at which sympathetic drive becomes the dominant factor in further cardiovascular responses. Data also suggest that sex differences in orthostatic tolerance may not be the result of anatomical and anthropometric differences. Finally, it is proposed that the discovered linkages between the two studied systems may reside in the insula, a structure deep in the brain with functions in both systems
Biological Roles of Bone Morphogenetic Protein 1 (BMP1) in Periodontium
No full textThis thesis explores the pivotal role of Bone Morphogenetic Protein 1 (BMP1) in the development and maintenance of the periodontium, employing Bmp1 conditional knockout (cKO) mouse models. The research involved creating a unique lineage of mice with a targeted deletion of the Bmp1 gene in dental follicle cells during early embryonic development, specifically in the progenitor cells destined to differentiate into alveolar bone osteoblasts, cementoblasts, and periodontal ligament (PDL) fibroblasts, known as Osr2-Cre;Bmp1^flox/flox mice. This study provides a detailed comparative analysis of the alveolar bone, cementum, and PDL structures in these Bmp1 cKO mice against normal control mice through various analytical methods, including plain x-ray radiography, histological examination, and immunohistochemical (IHC) analysis. Our findings reveal significant disruptions in PDL collagen fiber organization and bone matrix development, leading to substantial alveolar bone loss in Bmp1 cKO mice at both 6 and 24 weeks of age. Histological and IHC analyses highlighted a reduction in PDL integrity, abnormal protein distributions, and significant decreases in Dentin Matrix Protein 1 (DMP1) levels, suggesting BMP1's essential role in collagen synthesis and the overall mineralization process. Notably, irregular distribution patterns of periostin and fibrillin, underscore the profound impact of BMP1 deletion on dental morphology and periodontal health. The study conclusively demonstrates that BMP1 is critical for the structural integrity and functional maintenance of the periodontium, influencing various proteins involved in the development and health of the periodontal ligament and alveolar bone. The observed defects in Bmp1 cKO mice highlight the importance of BMP1 in collagen network maintenance and alveolar bone formation, with significant implications for periodontal disease pathology and treatment strategies. This research underlines the complex interplay between BMP1 and other proteins in periodontal development, providing invaluable insights into the mechanisms underpinning periodontal health and disease
A Numerical Study on the Multiline Ring Anchor in Sand
No full textThe Multiline Ring Anchor is an anchor solution designed to meet the growing demands of the offshore renewable energy sector in the country. It has been presented as an alternative to conventional anchor systems with its enhanced engineering efficiency and financial sustainability. The present doctoral work offers an assessment of the geotechnical performance of the anchor, to aid its transition from theory to practice.
A numerical study was undertaken to achieve a comprehensive understanding of the behavior of the anchor as a support system for arrays of offshore floating wind turbines. Its response under monotonic load conditions from different mooring systems is simulated using finite element analysis. The study was primarily divided into two phases ��� the first focused on the purely vertical capacity of the MRA in drained sand, with an emphasis on its end bearing behavior; and the second studied the response of the MRA when subjected to an inclined tensile pull while exploring the effects of the combination of loading conditions on it. Additionally, as a preliminary step in the analysis of the anchor under partial drainage conditions, a hypoplastic constitutive law is explored as an alternative to the Mohr Coulomb model.
The study finally presents a simple empirical model to estimate the vertical and the inclined ultimate capacities of the MRA in drained sands, along with a means to determine the optimum loading conditions, as functions of the padeye location and load inclination angle