Al-Si based alloys are commonly used in the automobile industry due to their superior properties, high strength to weight ratio, corrosion resistance, recyclability, etc. These alloys are fabricated by casting and powder metallurgy techniques in which porosity is a common feature. The presence of pores is accompanied by a decrease in mechanical properties, i.e., a drop in hardness and ductility of the materials. In the present study, an attempt was made to understand the effect of surface porosity on the tribological property. A380M and Al-6wt% Si alloys were used to prepare specimens containing 2.6 to 6.9% porosity via casting and 1 to 6.7% porosity via powder metallurgy techniques, respectively. Dry sliding wear behavior was investigated in the load range 6-20 N against an AISI 52100 bearing steel ball using a reciprocating ball-on-flat configuration at a frequency range of 4-20 Hz for cast and 15 Hz for P/M samples.

In order to understand the complex fracture network that controls water movement in Sherrod Area of Spraberry Field in West Texas and to better manage the on-going waterflood performance, a field scale inter-well tracer test was implemented. This test presents the largest inter-well tracer test in naturally fractured reservoirs reported in the industry and includes the injection of 13 different tracers and sampling of 110 producers in an area covering 6533 acres. Sherrod tracer test generated a total of 598 tracer responses from 51 out of the 110 sampled producers. Tracer responses showed a wide range of velocities from 14 ft/day to ultra-high velocities exceeding 10,000 ft/day with same-day tracer breakthrough. Re-injection of produced water has caused the tracers to be re-injected and added an additional challenge to diagnose and distinguish tracer responses affected by water recycling. Historical performance of the field showed simultaneous water breakthrough of a large number of wells covering entire Sherrod area. This research investigate analytical, numerical, and inversion modeling approaches in order to categorize, history match, and connect tracer responses with water-cut responses with the objective to construct multiple fracture realizations based entirely on water-cut and tracers‟ profiles. In addition, the research highlight best practices in the design of inter-well tracer tests in naturally fractured reservoirs through lessons learned from Sherrod Area. The large number of tracer responses from Sherrod case presents a case of naturally fractured reservoir characterization entirely based on dynamic data. Results indicates that tracer responses could be categorized based on statistical analysis of tracer recoveries of all pairs of injectors and producers with each category showing distinguishing behavior in tracers‟ movement and breakthrough time. In addition, it showed that tracer and water-cut responses in the field are dominantly controlled by the fracture system revealing minimum information about the matrix system. Numerical simulation studies showed limitation in dual porosity formulation/solvers to model tracer velocities exceeding 2200 ft/day. Inversion modeling using Gradzone Analysis showed that east and north-west of Sherrod have significantly lower pore volume compared to south-west.

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Modeling of airflow resistance in grain bulk requires knowledge of the tortuosity and velocity of the air flow through the grain bulk. In this study, experiments were carried out to determine these characteristics of airflow paths by analyzing digital images of smoke-visualized airflow paths inside a grain bulk obtained with a high speed camera. Colored smoke with approximately the same density as air was introduced into the test box for the visualization of the airflow through the grain bulk. Soybeans with a moisture content of 8.82% on wet basis were used in this study. The high quality videos obtained by recoding the fast movement of the smoke through the grain bulk was first separated into frames using a commercial software, VirtualDub (CRIM, Montreal, Québec, Canada), and the 512× 384 pixel RGB image files (frames) extracted from the recorded videos and read into ImageJ an image processing Java-based software developed by the United State National institute of Health, to track the movement of the smoke in the images, frame by frame to determine lengths, tortuosities of the different flow paths, as well as their velocities.

Permeability is that physical property of a porous medium that controls the flow of fluids through that medium. The flow of methane and water may be induced by the excavation of a mine opening in methane-bearing strata. Methane flow into a mine opening constitutes one of the biggest hazards in the coal mining industry. It is poisonous to humans and can ignite at concentrations as low as 5 % per volume and create explosions in the presence of coal dust from mining. If the flow of methane and/or water into the mine opening becomes blocked by an impervious layer, excessive pressures may develop, particularly in the roof strata of the mined seam, which can lead to roof falls. In order to characterize the flow of methane and water into and around the openings in a mine, that was plagued by roof falls suspected of being the result of excessive fluid pressure build-up, a large scale laboratory investigation of the permeability of the roof sediments of the working coal seam in the area was undertaken. The permeability was measured under atmospheric conditions by means of a modified Ohle permeameter, and under triaxial conditions with the aid of a modified Hoek cell. The permeability of the sediments towards methane and water was measured. Nitrogen was used as a control because it is much less reactive than methane towards the sediments used in this project. It was found that the permeability decreases with increasing gas pressure, in the case of gas being the permeating fluid, and increased with increasing water pressure, in the case of water being the permeating fluid. In some instances anomalous plots of permeability versus reciprocal mean gas pressure were obtained. These were attributed to the effects of methane adsorption or the Klinkenberg effect, and a possible method to determine which of the two processes is dominant is discussed. To characterize the flow in the roof strata of the coal seam being mined, the permeability was correlated to fades type. The different fades types were numbered from 1 to 14 with increasing grain size for ease of correlation. Due to the variable nature of the sediments, even in a fades type, no single permeability could be obtained for a fades type. Instead permeability ranges were obtained for each fades type. The definition of the lower and upper limits for each range were found to be dependant on the number of tests done on samples for that fades type. Nonetheless a relationship of increasing permeability with increasing grain size was found in the coarser grained fades (facies type 8 and higher). For the fIner grained fades types the permeability was found to decrease with increase in grain size. A graph could be constructed for use in predicting possible hazardous zones by identifying the fades type and then reading the permeability range that can be expected off the graph. Due to the variable nature of the sediments, the graph is, at this time, only applicable to the areas where the samples were obtained. A permeability prediction graph for all localities would be an ideal but is beyond the scope of this project. Such a graph, and the methods discussed have a wide range of applications in the coal mining and methane gas exploitation industries. / Thesis (M.Sc.)-University of Natal, Durban, 1994.

Nanocellulose has received considerable interest during the last decade because it is renewable and biodegradable, and has excellent mechanical properties, nanoscale dimensions and wide functionalization possibilities. It is considered to be a unique and versatile platform on which new functional materials can be based. This thesis focuses on nanocellulose from wood (NFC) and from Cladophora algae (CNC), functionalized with surface charges or coated with the conducting polymer polypyrrole (PPy), aiming to study the influence of synthesis processes on structural and electrochemical properties of such materials and assess their biocompatibility. The most important results of the work demonstrated that 1) CNC was oxidized to the same extent using electrochemical TEMPO-mediated oxidation as with conventional TEMPO processes, which may facilitate easier reuse of the reaction medium; 2) NFC and CNC films with or without surface charges were non-cytotoxic as assessed by indirect in vitro testing. Anionic TEMPO-CNC films promoted fibroblast adhesion and proliferation in direct in vitro cytocompatibility testing, possibly due to its aligned fibril structure; 3) Rinsing of PPy-coated nanocellulose fibrils, which after drying into free-standing porous composites are applicable for energy storage and electrochemically controlled ion extraction, significantly degraded the PPy coating, unless acidic rinsing was employed. Only minor degradation was observed during long-term ambient storage; 4) Variations in the drying method as well as type and amount of nanocellulose offered ways of tailoring the porosities of nanocellulose/PPy composites between 30% and 98%, with increments of ~10%. Supercritical CO2-drying generated composites with the largest specific surface area yet reported for nanocellulose/conducting polymer composites (246 m2/g). The electrochemical oxidation rate was found to be controlled by the composite porosity; 5) In blood compatibility assessments for potential hemodialysis applications, heparinization of CNC/PPy composites was required to obtain thrombogenic properties comparable to commercial hemodialysis membranes. The pro-inflammatory characteristics of non-heparinized and heparinized composites were, to some extent, superior to commercial membranes. The heparin coating did not affect the solute extraction capacity of the composite. The presented results are deemed to be useful for tuning the properties of systems based on the studied materials in e.g. energy storage, ion exchange and biomaterial applications.

Surface mining of the Athabasca Oil Sands of Canada is occurring at an unparalleled rate resulting in large scale disturbances over vast areas. Soil water availability for plants is one of the key issues faced when reclaiming the landscape. A factor which limits the soil water availability is soil water repellency (SWR). Soil water repellency is found on both natural and disturbed sites in this region and can cause reduced infiltration, reduced soil water storage, enhanced runoff, increased preferential flow, and reduced ecosystem productivity. Effective characterization of SWR, determination of the causes of SWR and understanding how it affects soil pores and water flow are important for environmental management. The main objective of this study is to examine the effect of SWR and fungal hydrophobicity on soil water dynamics in Athabasca Oil Sands. This was accomplished by determining the relationship between the measurement of severity and persistence of SWR and the critical water content (CWC) where SWR is greatest between different soils in the region. Examining how the water conducting porosity and soil pores are affected by SWR. Developing methods to quantify fungal strains that cause SWR and testing of these fungal strains for their ability to alter the SWR and infiltration into soil. Results show that a high severity (Contact angle) of repellency does not necessarily denote long persistence (Water Drop Penetration Time) or high CWC in soils from the region. A high severity of SWR in larger diameter pores decreased the water conducting porosity due to the larger pore contribution to the total liquid flux. The modified microscopy approach and the alcohol percentage test (APT) resulted in improved characterization of fungal hydrophobicity. Fungal strains were classified as hydrophilic, hydrophobic and chrono-amphililic based on their surface properties from these measurements. The surface property of selected fungi strains can alter the SWR in both a repellent and wettable soil and can also change the water infiltration rate. This research highlights the importance of characterization of SWR, the effects on water flow, and how fungal hydrophobicity can alter the SWR and infiltration. This will aid in improving our understanding of SWR and improve remediation efforts on water repellent soils in the Athabasca Oil Sands region.

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The purpose of this study was to investigate the velocity distribution through an annular bed packed randomly with equal sized spheres. Extensive research has been conducted on the velocity distribution inside packed beds packed with equal sized spheres, different sized spheres, deformed spheres, cylinders and Raschig-rings. A majority of these experimental and numerical studies focused on the cylindrical packed bed. These studies and numerical models are all confined to the velocity profile once the fluid flow is fully developed. The development of the velocity through the inlet region of the bed and the fluid flow redistribution in the outlet of the bed is thus neglected. The experimental investigation into the velocity distribution down stream of the annular packed bed of the HTTU indicated that the velocity profile was independent of the mass flow rate for a particle Reynolds number range of 439 £ Re £ 3453 . These velocity profiles did not represent the distribution of the axial velocity due to shortcomings associated with the single sensor hot wire anemometry system used to measure the velocity distribution. A numerical investigation, using the RANS CFD code STAR-CCM+®, into the velocity distribution downstream of an explicitly modelled bed of spheres indicated that the axial velocity distribution could be extracted from the experimental velocity profiles by using an adjustment factor of 0.801. This adjusted velocity profile was used in the verification of the implicit bed simulation model. The implicit bed simulation model was developed in STAR-CCM+®. The resistance of the spheres was modelled using the KTA (1981) pressure drop correlation and the structure of the bed was modelled using the porosity correlation proposed by Martin (1978), while the effective viscosity model of Giese et al. (1998), adjusted by a factor of 0.8, was used to model the velocity distribution in the near wall region. It was found that the structure in the inlet region of the bed, where two walls disturb the packing structure, can be modelled as the weighted average of the radial and axial porosity while the structure in the outlet regions can be modelled by letting the radial porosity increase linearly to unity. The basic shape of the velocity profile is established immediately when the fluid enters the bed. The amplitude of the velocity peaks however increase in magnitude until the velocity profile is fully developed at a distance approximately of five sphere diameters from the bed inlet. The profile remains constant throughout the bed until the outlet region of the bed is reached. In the outlet region a significant amount of fluid redistribution is observed. The amplitude of the velocity peaks is reduced and the position of the velocity peaks is shifted inwards towards the centre of the annular region. The fully developed velocity profile, predicted by the simulation model is in good agreement with profiles presented by amongst others Giese et al. (1998). The current model however also offers insight into the development of the profile through the inlet of the bed and the fluid redistribution, which occurs in the outlet region of the bed. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.