Application of the Variational Fracture Model to Hydraulic Fracturing in Poroelastic Media

Hydraulic fracturing has persisted through the use of simple numerical models to describe fracture geometry and propagation. Field tests provide evidence of interaction and merging of multiple fractures, complex fracture geometry and propagation paths. These complicated behaviors suggest that the simple models are incapable of serving as predictive tools for treatment designs. In addition, other commonly used models are designed without considering poroelastic effects even though a propagating hydraulic fracture induces deformation of the surrounding porous media. A rigorous hydraulic fracturing model capable of reproducing realistic fracture behaviors should couple rock deformation, fracture propagation and fluid flow in the both the fracture and reservoir. In this dissertation, a fully coupled hydraulic fracturing simulator is developed by coupling reservoir-fracture flow models with a mechanical model for reservoir deformation. Reservoir-fracture deformation is modeled using the variational fracture model which provides a unified framework for simultaneous description of fracture deformation and propagation, and reservoir deformation. Its numerical implementation is based on a phase-field regularized model. This approach avoids the need for explicit knowledge of fracture location and permits the use of a single computational domain for fracture and reservoir representation. The first part of this work involves verification of the variational fracture model by solving the classical problem of fracture propagation in impermeable reservoirs due to injection of an inviscid fluid. Thereafter, the developed reservoir-fracture model is coupled to the mechanical model. Iterative solution of the variational fracture model and the coupled flow model provides a simplified framework for simultaneous modeling of rock deformation and fluid flow during hydraulic fracturing. Since the phase field technique for fracture representation removes the limitation of knowing a priori, fracture direction, the numerical solutions provide a means of evaluating the role of reservoir and fluid properties on fracture geometry and propagation paths. First, the proposed approach is validated for simple idealized scenarios for which closed form solutions exist in the literature. Further simulations highlight the role of fluid viscosity and reservoir properties on fracture length, fracture width and fluid pressure. Numerical results show stress shadowing effect on multiple hydraulic fracture propagation. Finally, the effect of in situ stress on fracture propagation direction is reproduced while the role of varying reservoir mechanical properties on fracture height growth is investigated

Shape Optimization for Drag Minimization Using the Navier-Stokes Equation

Fluid drag is a force that opposes relative motion between fluid layers or between solids and surrounding fluids. For a stationary solid in a moving fluid, it is the amount of force necessary to keep the object stationary in the moving fluid. In addition to fluid and flow conditions, pressure drag on a solid object is dependent on the size and shape of the object. The aim of this project is to compute the shape of a stationary 2D object of size 3.5 m2 that minimizes drag for different Reynolds numbers. We solve the problem in the context of shape optimization, making use of shape sensitivity analysis. The state variables are fluid pressure and velocity modeled by the Navier-Stokes equation with cost function given by the fluid drag which depends on the state variables. The geometric constraint is removed by constructing a Lagrangian function. Subsequent application of shape sensitivity analysis on the Lagrangian generates the shape derivative and gradient. Our optimization routine uses a variational form of the sequential quadratic programming (SQP) method with the Hessian replaced by a variational form for the shape gradient. The numerical implementation is done in Python while the open source finite element package, FEniCS, is used to solve all the partial differential equations. Remeshing of the computational domain to improve mesh quality is carried out with the open source 2D mesh generator, Triangle. Final shapes for low Reynolds numbers resemble an american football while shapes for moderate to high Reynolds numbers are more streamlined in the tail end of the object than at the front

Pore-scale lattice Boltzmann simulations of inertial flows in realistic porous media: a first principle analysis of the Forchheimer relationship

With recent advances in the capabilities of high performance computing (HPC) platforms and the relatively simple representation of complex geometries of porous media, lattice Boltzmann method (LBM) has gained popularity as a means of solving fluid flow and transport problems. In this work, LBM was used to obtain flow parameters of porous media, study the behavior of these parameters at varying flow conditions and quantify the effect of roughness on the parameters by relating the volume averaged flow simulation results to Darcy and Forchheimer equations respectively. To validate the method, flow was simulated on regular and random sphere arrays in cubic domains, for which a number of analytical solutions are available. Permeability and non-Darcy coefficients obtained from the simulation compared well with Kozeny and Ergun estimates while deviation from the observed constant permeability and tortuosity values occurred aroundRe≈1-10. By defining roughness as hemispherical protrusions on the smooth spheres in the regular array, it was observed from flow streamlines obtained at different roughness heights that the average length of the flow paths increased with increasing roughness height. As such, the medium tortuosity and non-Darcy coefficient increased while the permeability decreased as height of the roughness increased. Applying the method to a 3D computed tomography image of Castlegate sandstone, the calculated macroscopic permeability and beta factor components were in good agreement with reported experimental values. In addition, LBM beta factors were compared with a number of empirical models for non-Darcy coefficient estimation and were found to be of the same order of magnitude as most of the correlations, although estimates of the models showed wide variation in values. Resolution of the original sample was increased by infilling with more voxels and simulation in the new domain showed better flow field resolution and higher simulated flow regimes compared to those of the original sample, without significant change in the flow parameters obtained. Using the Reynolds number based on the Forchheimer coefficient, the range of transition from Darcy to non-Darcy regime was within the values reported by Ruth and Ma (1993) and Zeng and Grigg (2006).

Stimulated Biodegradation of Spent Lubricating Motor oil in Soil Amended with Animal droppings.

The potentials of organic wastes from animal droppings as bioremediation alternative for soils spiked with waste-lubricating motor oil (spent oil) was evaluated. The rate of biodegradation of the spent oil was studied for a period of 6 months under laboratory condition. The result of the microbial counts for soils spiked with 5000 mgkg-1(0.5%) spent oil has its total heterotrophic bacterial count in  unamended control soil ranging from 2.71±0.09 to 7.21±0.25 x 106 CFU/g  of soil, while those of soil amended with cow droppings (CD) ranged from 16.0±1.01 to 47.90±0.36x 106 CFU/g of soil and those of soil amended with goat droppings (GD) and  poultry manure(PM) ranged from 16.6±0.6 to 57.9±0.15 x 106 and 18.00±0.20×106 to 60.80± 1.19 ×106 CFU/g of soil respectively. The counts of hydrocarbon-utilizing bacteria (HUB) in unamended control soil ranged from 0.93±0.11 to 2.10±0.15 ×106 CFU/g of soil. The count of HUB in PM amended soil was significantly higher than those amended with goat droppings (GD), while those of goat dropping were higher than those of cow dung. The HUB count in GD amended soil ranged from 8.07±0.12x106 to 67.70±0.68 x 106 cfu/g of soil. The THB and HUB counts for soils spiked with 25000 mg/kg (2.5%) spent oil exhibited a similar trend as was observed for soil spiked with 0.5% spent oil. Evaluation by the first-order kinetic model which utilized combined data for the entire period revealed that PM with biodegradation rate constant of 0.2332 day-1 and half-life of 2.97days was better in stimulating biodegradation of oil at higher concentration, while GD with a biodegradation constant of 0.3253day-1 and half-life of 2.13 days performed better at low pollution when compared to that of PM and CD. Keywords: Biodegradation, waste-lubricating oil, Bacteria, Organic waste, Hydrocarbon

Quantitative Techniques’ and Production Planning and Control: An Empirical Analysis of Practice by Selected Nigerian Small-Scale Industries (2002-2006)

Empirically, analysis was made from results of 160 randomly chosen companies from eight purposively selected Nigerian small-scale industries to assess the available quantitative techniques (QTs) applicable to Production Planning and Control (PPC). It also examined whether, Qualitative Techniques are applied by the studied companies and the actual number of these companies that apply Qualitative Techniques, as well as factors inhibiting the use of Qualitative Techniques.A wide range of 11 Qualitative Techniques (QTs) tools were found to be applicable to Production Planning and Control with 35(23.2%) of the companies actually applying QTs. 3 factors were also found as inhibiting factors. Keywords: Quantitative Technique, Production Planning and Control, Small-scale Industry

Hepatoprotective effect of the ethanolic extract of Jatropha tanjorensis on acetaminophen-induced toxicity in rat model

The hepatoprotective activity of ethanolic leaf extract of Jatropha tanjorensis (ELEJT) against acetaminophen induced hepatotoxicity using Swiss albino rats was ascertained. The animals were grouped into six with five animals each. Hepatoprotection against acetaminophen-induced toxicity was evaluated using standard methods. Effect on genotoxicity using micronucleus test and spermatogenesis was ascertained. ELEJT significantly (p˂0.05) decreased the levels of serum liver enzymes. At 800 mgkg-1, ELEJT significantly (p˂0.05) reduced triacylglycerol and LDL levels but significantly (p˂0.05) increased the level of HDL compared to the toxin control group. Administration of ELEJT resulted in a dose-dependent increase in the total protein level. Sperm head abnormality was observed more at 800 mgkg-1 while at 400 mgkg-1 binucleated cell and micronuclei cells were detected. ELEJT exhibited hepatoprotective activity against Acetaminophen-induced liver damage using Swiss albino rats. This validates the traditional use of Jatropha tanjorensis in management of liver ailments and improvement of spermatogenesis. However, more work is needed to ascertain its mode of action.Keywords: Spermatogenesis, Hepatoprotective, Genotoxicity, Acetaminophe

Sociodemographic characteristics, distance to the clinic, and breast cancer screening results

Timely detection and follow-up of abnormal cellular changes can aid in early diagnosis of breast cancer, thus leading to better treatment outcomes. However, despite substantial breast cancer screening initiatives, the proportion of female breast cancer cases diagnosed at late stages remains high. Distance to screening clinics may affect access to care, particularly for women living in impoverished areas with limited means of reliable transportation. Utilizing breast cancer screening data collected by the Illinois Breast and Cervical Cancer Program between 1996 and 2010, we examined the effect of travel distance to the clinic from which women received breast cancer screening tests on stage of diagnosis. The proportion of abnormal mammograms in White women (1.6%) was higher than in Black women (1.1%) or Hispanic women (0.5%). The average distance traveled to a clinic was also farthest among White women (6.7 mi) than for Hispanic (5.3 mi) or Black women (4.4 mi). Distance to a clinic was significantly associated with increased odds of having abnormal results. When distance to clinic was controlled for, the observed disparity in odds of having an abnormal mammogram between White and Black women was no longer statistically significant. Individual and neighborhood sociodemographic characteristics were significantly associated with distance to clinic, but were not associated with increased odds of having an abnormal mammogram, controlling for distance to the clinic. Findings showed that individual and neighborhood sociodemographic characteristics are directly and indirectly associated with abnormal mammogram results, and that distance to a clinic may mediate, in part, the effects of individual characteristics and neighborhood disadvantage on the probability of having an abnormal mammogram

Racial Disparities in Breast Cancer Survival: The Mediating Effects of Macro-Social Context and Social Network Factors

ABSTRACT This study attempts to clarify the associations between macro-social and social network factors and continuing racial disparities in breast cancer survival. The study improves on prior methodologies by using a neighborhood disadvantage measure that assesses both economic and social disadvantage and an ego-network measurement tool that assesses key social network characteristics. Our population-based sample included 786 breast cancer patients (nHWhite=388; nHBlack=398) diagnosed during 2005-2008 in Chicago, IL. The data included census-derived macro-social context, self-reported social network, self-reported demographic and medically abstracted health measures. Mortality data from the National Death Index (NDI) were used to determine 5-year survival. Based on our findings, neighborhood concentrated disadvantage was negatively associated with survival among nHBlack and nHWhite breast cancer patients. In unadjusted models, social network size, network density, practical support, and financial support were positively associated with 5-year survival. However, in adjusted models only practical support was associated with 5-year survival. Our findings suggest that the association between network size and breast cancer survival is sensitive to scaling of the network measure, which helps to explain inconsistencies in past findings. Social networks of nHWhites and nHBlacks differed in size, social support dimensions, network density, and geographic proximity. Among social factors, residence in disadvantaged neighborhoods and unmet practical support explained some of the racial disparity in survival. Differences in late stage diagnosis and comorbidities between nHWhites and nHBlacks also explained some of the racial disparity in survival. Our findings highlight the relevance of social factors, both macro and inter-personal in the racial disparity in breast cancer survival. Findings suggest that reduced survival of nHBlack women is in part due to low social network resources and residence in socially and economically deprived neighborhoods. Our findings indicate that, to improve survival among breast cancer patients, policies need to focus on continued improvement of access to care and reduction of racially patterned social and economic hardship. Additionally, our findings support the need for health care providers to assess social support resources of breast cancer patients at the time of diagnosis

Social Support Needs of Minority Breast Cancer Patients: Significance of Racial Homogeneity and Kin Composition of Social Networks

Social support from family and friends assists breast cancer patients navigate a life crisis, but more needs to be understood about specific social network characteristics that can benefit breast cancer patients. To address this need, the primary aim of this study was to identify social network factors that facilitate or reduce social support. Given racially patterned gaps in social support among breast cancer patients, a secondary goal was to identify network characteristics that are linked to gaps in support. We examined these research questions using data from a sample of 915 breast cancer patients (NHWhite=373; NHBlack=377; Hispanic=165) and 4,021 of their network members. To improve on prior research, we collected detailed social network data using a personal-network measurement tool and assessed needed and received support on five support components. Study findings identified specific network characteristics that facilitate these social support components. Network size was associated with increased practical, informational, emotional, and spiritual support. Network density was associated with increased practical support. Racial homogeneity in networks were associated with reduced informational support while a higher number of daughters in support networks was associated with increased emotional support. Compared to NHWhite patients, NHBlack patients were more likely to experience inadequate practical and financial support. Additionally, compared to NHWhite patients, Hispanic patients were more likely to experience inadequate informational and emotional support. The study found that network density, racial homogeneity, and gender composition of NHWhite, NHBlack and Hispanic social networks contributed to the racially patterned disparities in social support. Findings in this study could inform interventions aimed at increasing social support through greater mobilization of existing network ties as well as policy-driven, formal community building initiatives aimed at replicating benefits of naturally occurring networks

Influence of Personality and Educational Level on Nigerian Consumers Preference for Foreign Goods

This study examined the Influence of Educational Level and Personality on Nigerian Consumer for Foreign Goods. The study used 253 final year students of Nnamdi Azikiwe University, Ordinary National Diploma Students (OND) and Higher National Diploma Students (HND) of Federal Polytechnic Oko, both in Anambra State of Nigeria. The sample was selected through convenient sampling technique. The participants were composed of 51% male and 49% female students; between the age ranges of 19 to 30 years. The mean and standard deviation of their ages were 23.31 and 4.67. The study used Eysenck Personality Questionnaire (E.P.Q) (adult form) and Consumer Perception Scale (C.P.S) to measure the variables of interest. A two-way Analysis of Variance (ANOVA) statistics was used to analyse data gathered from the scales administered. The study found that personality traits and educational level individually, have significant influence on Nigerian consumers’ preference for foreign goods, at .05 level of significance. Keywords: Personality, Educational level, Consumers, Foreign Good