Browsing by Subject "In-situ"
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Item Direct in-situ evaluation of liquefaction susceptibility(2014-05) Roberts, Julia Nicole; Stokoe, Kenneth H.Earthquake-induced soil liquefaction that occurs within the built environment is responsible for billions of dollars of damage to infrastructure and loss of economic productivity. There is an acute need to accurately predict the risk of soil liquefaction as well as to quantify the effectiveness of soil improvement techniques that are meant to decrease the risk of soil liquefaction. Current methods indirectly measure the risk of soil liquefaction by empirically correlating certain soil characteristics to known instances of surficial evidence of soil liquefaction, but these methods tend to overpredict the risk in sands with silts, to poorly predict instances of soil liquefaction without surface manifestations, and fail to adequately quantify the effectiveness of soil improvement techniques. Direct in-situ evaluation of liquefaction susceptibility was performed at a single site at the Wildlife Liquefaction Array (WLA) in Imperial Valley, California, in March 2012. The project included a CPT sounding, crosshole testing, and liquefaction testing. The liquefaction testing involved the measurement of water pressure and ground particle motion under earthquake-simulating cyclic loading conditions. The objective of this testing technique is to observe the relationship between shear strain in the soil and the resulting generation of excess pore water pressure. This fundamental relationship dictates whether or not a soil will liquefy during an earthquake event. The direct in-situ evaluation of liquefaction susceptibility approach provides a more accurate and comprehensive analysis of the risks of soil liquefaction. It also has the ability to test large-scale soil improvements in-situ, providing researchers an accurate representation of how the improved soil will perform during a real earthquake event. The most important results in this thesis include the identification of the cyclic threshold strain around 0.02% for the WLA sand, which is very similar to results achieved by other researchers (Vucetic and Dobry, 1986, and Cox, 2006) and is a characteristic of liquefiable soils. Another key characteristic is the 440 to 480 ft/sec (134 to 146 m/s) shear wave velocity of the soil, which are well below the upper limit 656 ft/sec (200 m/s) and an indication that the soil is loose enough for soil liquefaction to occur. The third significant point is that the compression wave velocity of the sand is greater than 4,500 ft/sec (1,370 m/s), indicating that it is at least 99.9% saturated and capable of generating large pore water pressure due to cyclic loading. These three conditions (cyclic threshold strain, shear wave velocity, and compression wave velocity) are among the most important parameters for characterizing a soil liquefaction risk and must all be met in order for soil liquefaction to occur.Item In-situ characterization of lanthanide electrodepositions(2021-01-25) Phelps, Clarice; Landsberger, Sheldon; Myhre, KristianThe electrodeposition process has been the standard method for producing actinide and lanthanide thin films for decades. The major benefits of the technique include high reproducibility, simple equipment set up, and high material utilization. The latter is important when producing actinide thin films of rare materials, which is the case for many actinide thin film targets for Super Heavy Element (SHE) research. Many techniques besides electrodeposition have been used for non-radioactive lanthanides and have shown to be most useful for radioactive lanthanides as well as enriched stable lanthanides due to the amount of available material. Despite its use for several decades, there is still a significant amount that is unknown about the actinide electrodeposition process. Consequently, it has become apparent that a deeper understanding of the electrodeposition process is necessary to produce films with improved properties. For example, greater adhesion could increase the lifetime of thin film targets irradiated on high current particle accelerators. For this reason, there are ongoing efforts to gain an understanding of the actinide electrodeposition process utilizing in-situ characterization techniques of lanthanide depositions. For rare actinide thin films, a lanthanide surrogate is desired to understand the morphology of the deposited material without depleting the amount of the rare actinide desired. This master’s thesis project will focus on the development of optical spectroscopy techniques for online monitoring of the electrodeposition process as well as address the proposed chemical form for the deposition of a lanthanide, and in turn, actinide electrodepositionItem Indirect selective laser sintering of ceramics(2021-12-08) Sassaman, Douglas Maxwell; Beaman, Joseph J.; Kovar, Desiderio; Seepersad, Carolyn; Ide, MatthewCeramics with intricate geometries are useful in a wide range of technical applications, but current manufacturing techniques limit the geometric complexity. Additive manufacturing (AM) is a viable approach to surmount these limitations and produce complex tailored structures. However, ceramic materials are not easily processed with AM technologies because of their high melting temperature and sensitivity to thermal shock. Because of this, an indirect approach is taken where a transient binder is added to effectively glues the ceramic particles together during shaping. Selective Laser Sintering (SLS) is capable of producing small complex polymer features, but how this capability translates to indirect SLS of ceramics is an open question. This dissertation aims to systematically investigate the limitations of using indirect SLS to produce intricate ceramic geometries. The investigation is first approached from a phenomenological perspective, where a variety of geometries are manufactured using indirect SLS and then compared to similar polymer parts produced with direct SLS. The geometry comparison is paired with a mechanistic study of particle-scale interactions using in-situ microscopy, and an analytical model is developed to describe these observations. Guidelines for the geometries possible with polymer SLS turn out to be a good starting place for the design and manufacture of ceramic geometries using indirect SLS. However, indirect SLS is further limited by the heterogeneity of the blended powder. In-situ microscopy shows that, in mixed polymer/ceramic powders, the binding mechanisms are different at different laser scan speeds and also different from polymer SLS or selective laser melting of metals. A permeation model is used to describe the binding mechanisms specific to indirect SLS and correctly predicted all of the trends observed in experiments. The settings (laser power and scan speed) that produced parts strong enough to be removed from the SLS machine were predicted by the model to produce permeation distances large enough for particle bonding. Conversely, settings which resulted in failed parts during the experiments were predicted by the model to not permeate far enough for particle bondingItem An integrated computational-experimental approach for the in situ estimation of valve interstitial cell biomechanical state(2016-05) Buchanan, Rachel Marie; Sacks, Michael S.; Baker, Aaron B; Stachowiak, Jeanne C; Moon, Tess J; Guilak, FarshidMechanical forces are known to regulate aortic valve interstitial cell (AVIC) functional state by modulating their biosynthetic activity, translating to differences in tissue composition and structure and, potentially, leading to aortic valve (AV) dysfunction. While advances have been made toward the understanding of AVIC behavior ex-situ, the AVIC biomechanical state in its native extracellular matrix (ECM) remains largely unknown. Consequently, changes in AVIC behaviors, such as stiffness and contractility, resulting from pathological cues in-situ remain unidentified. We hypothesize that improved descriptions of AVIC biomechanical state in-situ, obtained using an inverse modeling approach, will provide deeper insight into AVIC interactions with the surrounding ECM, revealing important changes resulting from pathological state, and possibly informing pharmaceutical therapies. To achieve this, a novel integrated numerical-experimental framework to estimate AVIC mechanobiological state in-situ was developed. Flexural deformation of intact AV leaflets was used to quantify the effects of AVIC stiffness and contraction at the tissue level. In addition to being a relevant deformation mode of the cardiac cycle, flexure is highly sensitive to layer-specific changes in AVIC biomechanics. As a first step, a tissue-level bilayer model that accurately captures the bidirectional flexural response of AV intact layers in a passive state was developed. Next, tissue micromorphology was incorporated in a macro-micro scale framework to simulate layer-specific AVIC-ECM interactions. The macro-micro AV model enables the estimation of changes in effective AVIC stiffness and contraction in-situ that are otherwise grossly inaccessible through experimental approaches alone. Finally, microindentation studies examining AVIC activation were run in parallel with in-situ studies to emphasize the necessity of an in-situ approach, and the advantage it affords over existing ex-situ methodology. In conclusion, the developed numerical-experimental methodology can be used to obtain AVIC properties in-situ. Most importantly, it can lead to further understanding of AVIC-ECM mechanical coupling under various pathophysiological conditions and the investigation of possible treatment strategies targeting the myofibroblast phenotype characteristic of early signs of sclerotic valvular disease.