Department of Ocean and Mechanical Engineering

In this research, we use calcite and celestite inorganic model systems to better understand biological crystallization in the presence of organic biomolecules. Our goal is to understand what happens when biomolecules occlude into crystals and how that affects the structural organization. Specifically, we focus on the role the respective biomolecule chemistry plays in regulating the incorporation into a crystal. To visualize and characterize the biomolecule/mineral role in crystallization, a variety of techniques were used to image and analyze the respective model systems. The synthesized single crystals were characterized by light microscopy (LM). Scanning electron microscopy (SEM) and field-emission SEM (FE-SEM) were used to examine the morphology of the crystals. Structural and topographical analyses were carried out using atomic force microscopy (AFM). Fourier transform infrared spectroscopy (FTIR) and confocal Raman microscopy were both used to characterize functional groups, where Raman spectroscopic mappings provided the region-specific chemical composition of the crystal.

This research studied the effects of mooring line pretension, spring safe working load, and spring response curve on peak loads and platform surge. The maximum tension load from the optimized assembly was applied to a modelled section of 8-strand multiplait rope to study stress concentrations. The analyses yielded a mooring line pretensioned at 1250 kN with a 4500 kN safe working load degressive spring was optimal. Fatigue damage from 12-hour duration of 50-year storm conditions was 8.04 × 10−6. Infinite life is predicted at annual average conditions. The peak tension from 50-year storm conditions of 3671 kN and annual average conditions of 1388 kN was applied to the section model, yielding a maximum stress of 3.70 × 108 Pa and 2.01 × 108 Pa, respectively, from friction and longitudinal compression of the rope’s cross section. The maximum stress from the static structural analysis was 33.5% of polyester’s ultimate strength, based on the maximum stress failure criterion.

Traditional techniques of observing cracking within reinforced structures can be invasive, leading to an increased risk of added corrosion to structures already undergoing corrosive processes. The research presented in this document improves upon a nondestructive method for detecting early crack formation in reinforced concrete. This method includes using acoustic signaling to add a layer of salt water between the sensor and analyzed sample. Following the collection of surface and rebar echo responses, an adapted version of the novel Biot-Stoll method is used to model sound propagation for poro-elastic mediums. Testing of model parameters and variables has improved the root mean square error (RMSE) by up to 63.7% when studying the full signal, and up to 62.6% for the rebar echo locations. These improvements signify better curve fitting between simulated and measured responses, which lead to increased accuracy in the model parameter outputs.

Reinforced concrete (RC) is the building block of modern architecture and industry. The failure of which is costly and dangerous. Typically made with carbon steel rebars, corrosion resistant alloys provide an alternative method of delaying failure. Stainless steels, while more expensive than carbon steels, provide excellent corrosion resistance, but less is known about the long term monitoring of corrosion activity for stainless steel than for carbon steel. This study looks at samples prepared between 2005 and 2009 using 304SS, 316SS, and 2304SS rebars, as well as SMI and Stelax stainless steel clad carbon steel reinforcements embedded in three different concrete mixes. These selected samples are split into two exposure environments, inside humidity chambers within the laboratory and outdoor exposure. Measurements reported here were made monthly over the course of 250 plus days using the Galvanostatic Pulse method, Electrochemical Impedance Spectroscopy, and a Gecor 8 device. These methods were used to determine corrosion current, isolated corrosion current density, and solution resistance.
Corrosion current density values calculated from measurements by the Galvanostatic Pulse and Electrochemical Impedance Spectroscopy method are too small to indicate corrosion, based on value ranges provided by Andrade. However, Gecor 8 corrosion current density values indicate low levels or moderate levels of corrosion for all samples compared to the Andrade’s value ranges. The area used by the Gecor is unknown, so it’s possible this is driving up the measured values.

The lack of physiologically relevant human esophageal cancer models has as a result that many esophageal cancer studies are encountering major bottleneck challenges in achieving breakthrough progress. To address the issue, here a 3D esophageal tumor tissue model was engineered using a biomimetic decellularized esophageal matrix in a customized bioreactor. To obtain a biomimetic esophageal matrix, a detergent-free, rapid decellularization method was developed to decellularize porcine esophagus. The decellularized esophageal matrix (DEM) was characterized and the DEM was utilized for the growth of esophageal cancer cell KYSE30 in well plates and the bioreactor. Then the expression of cancerrelated markers of KYSE30 cells was analyzed and compared with formalin-fixed, paraffin-embedded (FFPE) esophageal squamous cell carcinoma (ESCC) tissue biospecimens. Results show that the detergent-free decellularization method preserved the esophageal matrix components and effectively removed cell nucleus. KYSE30 cancer cells proliferated well on and inside the DEM. KYSE30 cells cultured on the DEM in the dynamic bioreactor show different cancer marker expressions than those in the static well plate, and also share some similarities to the FFPE-ESCC biospecimens.

In this thesis, feasibility of a concept for launch and recovery of the Remus AUV from WAM-V USV is investigated. A modular recovery system which can be added to the WAM-V payload tray was designed, and based on a review of previous literature a CONOPS was developed for the launch and recovery process. The first phase of the CONOPS, which pertains to the position of the REMUS initially on the free surface prior to sling engagement is simulated using ANSYS AQWA. Preprocessing for the simulation involved simplification of the model in ANSYS SpaceClaim to achieve a proper mesh as well as theoretical calculations of the input parameters for wave environment and point masses etc. The simulation was evaluated by taking into consideration two wave environment scenarios: beam sea’s (-90 degrees) and head seas (0 degrees). The wave environment was based on a linear frequency range for the waves which considered wavelengths that correspond to half and double the length of the WAM-V 16’. The significance of the simulation is characterized through identifying the ideal direction and wave frequency range for recovery based on the RAOs of the two vehicles.

Rapid and efficient vascularization is still a considerable challenge of a tissue engineered β-tricalcium phosphate (β-TCP) scaffold. To overcome this challenge, branched channels were created in the porous scaffold to stimulate the instant flow of blood supply. The branched channeled porous β-TCP scaffold was fabricated using 3D printing and template-casting method. Human bone mesenchymal stem cells (hBMSC) and human umbilical vein endothelial cells (HUVEC) were seeded in the scaffolds and characterized through double-stranded DNA (dsDNA) assay, alkaline phosphatase (ALP) assay and cell migration. Scaffolds were then implanted in the subcutaneous pockets in mice. Hematoxylin and eosin staining and Immunohistochemical staining on vascularization, bone-related markers were carried out. Results showed that branched channels significantly promoted HUVECs’ infiltration, migration, proliferation, and angiogenesis and also promote the proliferation and osteogenesis differentiation of hBMSCs. Scaffolds did not show significant pro-inflammatory effects. In vivo results showed that in the early stage after implantation, cells significantly migrated into branched channeled scaffolds compared to non-channeled and straight channeled scaffolds. More and matured blood vessels formed in the branched channeled scaffolds compared to in non-channeled and straight channeled scaffolds. Besides promoting vascularization, the branched channels also stimulated the infiltration of bone-related cells into the scaffolds. These results suggested that the geometric design of branched channels in the porous β-TCP scaffold promoted rapid vascularization and potentially stimulated bone cell recruitment. To further enhance the function of the scaffold to promote the MSCs differentiation, MnO2 hollow and solid nanoparticles were doped into the scaffold with different concentrations.

The sensation of touch is an integral part of using our hands. As different researchers work toward the restoration of afferent sensation in prosthetic hands, it becomes urgent to better understand how an artificial hand’s afferent inputs are affected by the efferent muscular outputs, and vice-versa. Current methods of neuroprosthetic research have many regulatory hurdles, time, cost, and associated risk to the patient. To circumvent these hurdles, we developed a non-invasive, closed-loop (CL) neuroprosthetic research platform, integrating artificial tactile signals from an artificial hand with biomimetically-stimulated biological neuronal networks (BNNs) cultured in a multielectrode array (MEA) chamber. These living embodied biological computers (EBCs) can provide a non-invasive alternative for investigating invasive neuroprosthetic interfaces. With them we can explore a variety of control techniques, tactile sensation encoding methods, and neural decoding methods to increase the rate of research in this area with minimal regulatory approval, greatly reduced cost and time, and no risk to the patients. In the first stage of this integration, our EBC was programmed to embody neuronal spiking from spontaneously active “efferent” receptive fields in cultured BNNs as intentional signals for movement. Bursts were transferred to a robotic hand and initiated a tapping motion of the index finger laid in proximity to a surface. Contact elicited artificial sensations, which were registered by a biotac tactile sensor array fit to the robotic fingertip.

Characterization of the distribution and biophysical interactions of oceanic planktonic organisms is crucial to address fundamental science questions associated with climate change, marine ecology, pollution, and ocean optics. Thus, development of instrumentation techniques for monitoring plankton at high spatial and temporal resolutions is important. This dissertation deals with the advancements made in applying digital holography – a 3-D non-intrusive, freestream imaging technique – to address three different applications associated with marine plankton monitoring and ecology. In the first project, an autonomous in-line digital holographic microscope was successfully deployed for rapid in situ detection of the harmful dinoflagellate, Karenia brevis in the coastal Gulf of Mexico. Monitoring K. brevis abundance and distribution are crucial for early warning systems and implementing preventative measures to limit potential damage. The holographic system was successfully paired with a convolutional neural network for automated data processing to ensure rapid and accurate K. brevis detection.

The elevated energy demand and high dependency on fossil fuels have directed researchers’ attention to promoting and advancing hydraulic fracturing (HF) operations for a sustainable energy future. Previous studies have demonstrated that the particle suspension and positioning in slick water play a vital role during the injection and shut-in stages of the HF operations. A significant challenge to HF is the premature particle settling and uneven particle distribution in a formation. Even though various research was conducted on the topic of particle transport, there still exist gaps in the fundamental particle-particle interaction mechanisms. This dissertation utilizes both experimental and numerical approaches to advance the state of the art in particle-particle interactions in various test conditions. Experimentally, the study utilizes high-speed imaging coupled with particle tracking velocimetry (PTV) and particle image velocimetry (PIV) to provide a space and time-resolved investigation of both two-particle and multi-particle interactions during gravitational settling, respectively.