Transport Phenomena Modelled on Pore-Space Images

Fluid flow and dispersion of solute particles are modelled directly on three-dimensional pore-space images of rock samples. To simulate flow, the finite-difference method combined with a standard predictor-corrector procedure to decouple pressure and velocity is applied. We study the permeability and the size of representative elementary volume (REV) of a range of consolidated and unconsolidated porous media. We demonstrate that the flow-based REV is larger than for geometry-based properties such as porosity and specific surface area, since it needs to account for the tortuosity and connectedness of the flow paths. For solute transport we apply a novel streamline-based algorithm that is similar to the Pollock algorithm common in field-scale reservoir simulation, but which employs a semi-analytic formulation near solid boundaries to capture, with sub-grid resolution, the variation in velocity near the grains. A random walk method is used to account for mixing by molecular diffusion. The algorithm is validated by comparison with published results for Taylor-Aris dispersion in a single capillary with a square cross-section. We then accurately predict experimental data available in the literature for longitudinal dispersion coefficient as a function of Peclet number. We study a number of sandpack, sandstone and carbonate samples for which we have good quality three-dimensional images. There is a power-law dependence of dispersion coefficient as a function of Peclet number, with an exponent that is a function of pore-space heterogeneity: the carbonates we study have a distinctly different behaviour than sandstones and sandpacks. This is related to the differences in transit time probabilities of solute particles travelling between two neighbouring voxels. We then study the non-Fickian behaviour of solute transport in porous media by modelling the NMR propagators and the time-dependent dispersion coefficients of different rock types. The behaviour is explained using Continuous Time Random Walk (CTRW) theory: transport is qualitatively different for the complex porous media such as carbonates compared to the sandstone or sandpack, with long tailing and an almost immobile peak concentration. We discuss extensions of the work to reactive transport and the simulation of transport in finely-resolved images with billions of voxels

Nonlinear enthalpy transformation for transient convective phase change in Smoothed Particle Hydrodynamics (SPH)

A three-dimensional model is presented for the prediction of solidification behavior using a nonlinear transformation of the enthalpy equation in a Smoothed Particle Hydrodynamics (SPH) discretization. The effect of phase change in the form of release and absorption of latent heat is implemented implicitly as variable source terms in the enthalpy calculation. The developed model is validated against various experimental, analytical, and numerical results from the literature. Results confirm accuracy and robustness of the new procedure. Finally, the SPH model is applied to a study of suspension plasma spraying (SPS) by predicting the impact and solidification behavior of molten ceramic droplets on a substrate

Developing Optical Imaging Tools to Investigate Metabolic and Structural Biomarkers in Rodent Injury Models

Optical fluorescence imaging is one of the vastly growing fields of imaging used in a broad variety of preclinical investigation with great interest in translating its principles into clinical applications. Optical fluorescence imaging provides images of functional and structural changes with cellular and subcellular resolution in tissues at a low-cost. This technique takes advantage of the absorption of light photons at a specific wavelength by intrinsic or extrinsic fluorophores and emission of photons at characteristic wavelengths. The characteristics of the emitted wavelengths such as their energy and illuminance give substantial information of the imaged tissue. In the research presented here, we probe two Krebs cycle intrinsic fluorescence metabolic coenzymes, reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavin adenine dinucleotide (FAD) to study metabolic status changes during a human disease. The objective of my research can be categorized into two themes; I) Designing an optical imaging instrument called an in vivo fluorescence imager to quantitatively investigate the metabolic changes in tissue and customizing it to be suitable for human/clinical studies. II) Using optical imaging techniques to quantitatively investigate the 3D anatomical structure changes in vessel structure of organs. in vivo fluorescence imager can image many intrinsic and extrinsic fluorophores. However, we used it to track mitochondria bioenergetics NADH and FAD in wounds of diabetic mice. We also define the redox ratio (NADH/FAD) as a biomarker to investigate the effect of 670 nm photo-biomodulation in those wounds. In another study, we have used 3D optical imaging system on the biopsy of diabetic wounds to confirm the results from the in vivo fluorescence imager. It showed that our in vivo fluorescence imager could successfully track the changes in the metabolic state of non-treated and treated diabetic wounds with 670 nm photobiomodulation. Additionally, I validated a 3D vessel segmentation method developed in our lab by employing Murray’s law. Furthermore, I used the 3D optical cryo-imaging system and the segmentation method to quantitatively study the 3D vessel structure changes in irradiated animal model. The result of this study showed that radiation can adversely change the vasculature in irradiated kidneys and negatively affect kidney perfusion. In summary, my major contribution has been in device implementation and applications of imaging and image processing in studies of animal model diseases of humans

ADIABATIC SHEAR LOCALIZATION IN AISI 1340 AND 4340 STEELS: THE INFLUENCE OF MICROSTRUCTURE AND GEOMETRY

The mechanical behaviour of AISI 1340 and 4340 steel under high strain-rate loading in compression and in torsion were investigated using direct impact Hopkinson bar and torsion split Hopkinson bars. Both alloys contained 0.40 wt. % C, but different amounts and types of alloying additions. The materials are commonly used in high performance structural applications, where they could be subjected to dynamic shock loading. The objective of this study was to study the effects of microstructure, strain rates and specimen geometry on the occurrence and failure of adiabatic shear bands in these alloys under dynamic shock loading. Cylindrical specimens of the AISI 1340 alloys were heat treated to produce martensitic, dual-phase or pearlitic structure and subjected to impact loading at strain rates ranging between 1000 and 8000 /s. The martensitic test specimens were tempered at 205, 315 and 425 ºC to determine the effects of tempered condition on the adiabatic shear failure of the alloy. The effects of geometry on strain localization and adiabatic shear banding in both alloys were investigated by subjecting cylindrical-, cubical-, and truncated conical-shaped specimens to high velocity impact. The dynamic torsion test involved rapidly twisting of heat-treated thin-walled tubular specimens of the alloys and determining the damage evolution during the high strain torsional loading. Both optical and scanning electron microscopes were used to evaluate the damage evolution in the specimens after high strain rate loading. The types of shear band formed in the alloys depended on the microstructure and strain rate. Deformed bands were formed at low strain rates and there was a minimum strain rate required for formation of transformed band in both alloys. This minimum strain rate was highest in the specimens with pearlitic structure and lowest in the specimen with martensitic structure. The susceptibility of the martensitic specimens to the occurrence of transformed shear band decreased with increasing tempering temperature. Cracks were initiated and propagated along transformed bands leading to fragmentation under the impact loading. The susceptibility of the adiabatic shear bands to cracking was markedly influenced by strain-rates, initial microstructure and the specimens̕ geometry. The geometry of the impacted specimen determined the shape of the adiabatic shear band and the topography of the fracture surface of fragmented specimens. Fractographic investigation of fragmented specimens showed ductile shear failure and knobby fracture mode along the transformed band. Investigations of the transformed band using X-ray Photo Emission Electron Microscopy and Near Edge X-ray Absorption Fine structure Spectroscopy showed more nickel and less chromium inside the transformed bands in impacted AISI 4340 steel than in the region outside the shear band

Assessment of Combined Modality Therapy for Non-Small-Cell Lung Carcinoma: A Simulation Study Concerning Concurrent Chemo-Brachytherapy

Although surgery is the treatment of choice for early-stage non-small-cell lung carcinoma, almost two-thirds of patients do not have acceptable pulmonary function for extensive surgeries. The alternative approach for this large group of patients is sublobar resection along with low-dose-rate (LDR) brachytherapy (BT). However, patients with resected lungs have a high risk of recurrence and are often treated with platinum-based (Pt-based) chemotherapy (CT). In this study, we aimed to evaluate the absorbed doses of lung and other thoracic organs, considering concurrent chemo-BT with LDR sources in two modalities: conventional vs. unconventional Pt-based CT. We used the MCNPX code for simulations and to obtain the lung absorbed dose, dose enhancement factor (DEF), and Pt threshold concentration for the abovementioned modalities. Our results indicate that DEF correlates directly with Pt concentration at prescription point and is inversely correlated with depth. Dose enhancement for conventional CT concurrent with BT is \u3c 2%, while it is \u3e 2% in case of unconventional Pt-based CT wherein the Pt concentration exceeds 0.2 mg/g lung tissue. Also, the absorbed dose of healthy thoracic organs decreased by 2-11% in the latter approach. In conclusion, the concurrent chemo-BT in the lung environment could enhance the therapeutic doses merely by using unconventional CT methods, while lung Pt accumulation exceeds 0.2 mg/g

The feasibility of subirrigation systems on claypan soils in the Midwest

This was a study to evaluate the suitability of subirrigation along with alternative soil and water trujlnagement practices on claypan soil. Crop yields on these soils are usually low because of limited water management for crop production. Several years of crops, soil and weather data collected on a claypan soil in Illinois were used to study performance of subirrigation and conventional irrigation on these soils. Various drain spacings and depth combinations for both good and poor· quality surface drainage were simulated. Results indicated that optimum drain spacing for subirrigation on these soils would be 6 m under good surface drainage, and a weir setting depth of 35 cm on a 5-year recurrence interval basis. However, such a close drain spacing may not be economically feasible.U.S. Geological SurveyU.S. Department of the InteriorOpe

Comparison of Best Management Practice Adoption Between Virginia\u27s Chesapeake Bay Basin and Southern Rivers Watersheds

Producers in two regions of Virginia (Chesapeake Bay basin and Southern Rivers region) were surveyed to compare farming practices and agricultural best management practice (BMP) adoption. Objectives were to assess farming operations and determine the extent of cost-share and non-cost-share BMP implementation and gain insight into the impact of selected socioeconomic factors on the BMP adoption. Although farming characteristics and producer attitudes toward pollution and water quality were similar, BMP implementation differed between the two regions. Differences in BMP implementation may be due to a more focused, longer-term NPS pollution control educational effort in the Bay basin

Impact of medical scribes on dermatology trainee and attending experience

Background: Medical scribe integration into academic dermatology practices results in decreased attending documentation time, improved physician efficiency, and positive patient satisfaction. However, scribes' impact on dermatology education has not been explored. Methods: We conducted a cross-sectional survey at the Brigham and Women's Hospital Dermatology Department and its associated residency program assessing trainee and attending perceptions of scribe impact on documentation time, teaching time, and quality of teaching. Results: Thirty-nine surveys (67% of eligible population) were analyzed. The majority of faculty and trainees perceived that scribes decreased documentation time (92% attendings, 88% trainees), increased attendings' direct teaching time (57% attendings, 76% trainees), increased attending availability to answer questions (57% attendings, 68% trainees), and improved overall education (57% attendings, 80% trainees). Trainees generally perceived educational benefits of scribes more strongly than attendings. Trainees and attendings had discordant views regarding number of patients that the trainee sees (29% attendings, 72% trainees, P<0.05) and the amount of supervision provided for procedures (43% attendings, 56% trainees). Conclusions: The positive impact of scribes on dermatology education is consistent with results in other disciplines. Although hospitals typically invest in scribes to increase physician efficiency, this study suggests that scribes can also improve the educational experience