An investigation of chloride Ion levels In coarse colliery discards was undertaken because modem British Coal practice is to restore discard tips and lagoon embankments at an early stage in construction, commonly before much leaching has taken place. High chloride ion concentrations result in physiological drought and the failure of vegetation cover. Sites at two collieries were studied using grid and traverse (depth) sampling procedures. Results Indicate downward leaching of chloride ions into the embankment during Winter months and an increase in chloride levels towards the surface of the discard during dry, summer months. Salt hotspots occur on embankment surfaces during Summer months. These high chloride/sulphate concentrations represent the desiccation of seepages, most of which are related to embankment construction inadequacies, rather than to lagoons incorporated into the structure. Chlorides within the discard originate from formation waters intimately associated with Coal Measures sequences. In the eastern coalfields in particular, high chloride ion concentrations in the coal and waste rock from deep underground excavations are not removed by the coal washing processes. Consequently, they are retained in fresh colliery discards. Seasonal movements of chloride ions are associated with an increase In (negative) suction pressures within the near-surface layers of a colliery embankment. Suction pressures were monitored experimentally in two experimental tips and in the field at a third colliery site (Bilsthorpe Colliery). On an annual basis, suction pressures become operative early in April, reversing to residual negative or small positive pore pressures in mid-September. The leaching of chlorides from discard embankments is a function of the drainage characteristics of the materials and in clayey discards leaching to low levels is shown to take 5 to 7 years. Hotspots do not decrease significantly. The results of the present investigation can be applied to current embankment restoration schemes. In particular, the sowing of an embankment during the Autumn window, when electrolytes move downwards into the structure, would enable young vegetation to become established before being subjected to the higher Summer chloride concentrations. Hotspots require individual field drainage treatment.

Geomembranes (GMB) are normally used as part of the liner system in heap leach pads. There is a need to quantify tensile strains in the geomembrane that could affect short-term puncture and long-term performance of the GMB. In this thesis, short-term tensile strains arising from indentations caused from the material placed both below and above the geomembrane are quantified, and the potential for puncturing is investigated. Experiments were conducted on 1.5 mm high-density (HDPE) and liner low density polyethylene (LLDPE) geomembranes for applied pressures up to 3000 kPa. The geomembrane punctured from underliner material having gravel and sand placed directly beneath the geomembrane and a peak tensile strain of 40% was induced. Increasing the sand fraction to obtain a well graded gravel and sand underliner resulted in peak tensile strains of 14% in the geomembrane and caused no puncture. When geomembrane is underlain by geosynthetic clay liner (GCL) and compacted clay liner, the tensile strains increased with increasing deformability (due to higher water content) of the underlying material. Experiments were also conducted to examine the implications of overliner material and pressure on geomembrane strains. It was found that the overliner having gravel and some sand resulted in 18% tensile strain in the geomembrane at 2000 kPa and 27% for 3000 kPa. A gravelly sand overliner with some silt induced tensile strains of 9% and 12% at 2000 kPa and 3000 kPa respectively. None of the overliners was able to limit stains in the geomembrane to less the maximum recommended geomembrane strain proposed in the literature. A 150-mm-thick silty sand layer placed above coarsest overliner examined reduced the geomembrane strains to 2%, even when subjected to pressures of 3000 kPa. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-02-01 10:33:47.733

In this paper we explore Fibonacci heaps and their variants. The alternative versions of the Fibonacci heap, the thin and thick heaps, were introduced by H. Kaplan and R. E. Tarjan in 2008. We compare these heaps from both experimental and theoretical point of view and we also include some classic types of heaps, namely regular and pairing heap. In our experiments we will be most interested in the total time required to run an algorithm that works with heap. The results show that thin and thick heaps are usually faster than the Fibonacci heap and slower than the regular heap. In conclusion, we summarize the knowledge gained from experiments.

Thesis advisor: Alan Kafka / Heap leach flow patterns are governed by hydrogeological parameters including, soil properties, saturated and unsaturated hydraulic conductivity, initial degree of saturation, and the method of irrigation. Optimizing production during leaching cycles requires knowledge of the hydrogeological parameters of the leach heap, and their effect on flow behavior. This thesis research involved quantifying the flow rates of unsaturated homogenous soil profiles. Finite element numerical modeling has been utilized to simulate 1-dimensional unsaturated transient vertical flow. A series of parametric studies were conducted to examine how various soil properties and differing initial and boundary conditions affect percolation and flow. Results indicate that flow and percolation are increased or impeded based on the saturated and unsaturated parameters of the soil profile. Sensitivity analysis illustrates that the initial degree of saturation affects hydraulic behaviour relative to soil hydraulic conductivity, matric potential (negative pressure head), and the method of irrigation. At the initial stage of the research, some analyses indicated that numerical instabilities may occur within simulations due to selected mesh density, initial time step length, error tolerance, and the selected form of the unsaturated Richards Equation. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

No description available.

The abiotic leaching behavior of a chalcopyrite ore, from Asarco’s Ray-Mine, was conducted in shake flasks and miniature columns at elevated temperatures. The shake flask tests, with an ore particle size of 1.18mm-2.38mm, found the highest Cu extraction was obtained using 1M NaCl in a 9.8g/L sulphuric acid solution at 60°C, with 69% Cu extracted in 16 days. The next highest extraction, 59% Cu extracted in 16 days, was achieved by adding fine pyrite at a 4:1wt ratio with the chalcopyrite content, in a 9.8g/L sulphuric acid solution at 60°C. Flask tests using other lixiviants and additions found copper extractions in the range of 30-40% Cu after 16 days. In the mini-column tests, the rates of copper extraction were similar for all test conditions. The rate of Cu extraction, even with a small particle size of 1.18mm-2.38mm and an elevated temperature of 50°C, was slow for all test conditions with an average rate of ~0.15% Cu per day. The conceptual engineering of a hot, abiotic heap-leach for low-grade chalcopyrite ore, including hypothetical heat and mass balances was conducted. The leaching time for a commercial operation was estimated from published data on laboratory column leaching of chalcopyrite ores and extrapolated to a commercial heap-leach by analogy with known leaching times for chalcocite ores. In commercial abiotic heap-leaches of chalcopyrite ore, the partial oxidation reactions generate insignificant heat to maintain an elevated heap temperature therefore the heat required to maintain the elevated temperature must be provided externally. In commercial biotic chalcopyrite heap-leaches, the in-situ total oxidation reaction generates more heat than the abiotic reactions but is still insufficient to rapidly raise and maintain an elevated heap temperature. For a low-grade Chalcopyrite heap-leach the most practical method of providing this heat is by injecting steam into the base of the heap using current air injection pipes. An external oxidant is required and for an abiotic heap-leach external ferric generation will be required. / Thesis (Master, Mining Engineering) -- Queen's University, 2011-02-15 15:59:38.15

As an alternative to the Fibonacci heap, and a variation of the 2-3 heap data structure by Tadao Takaoka, this research presents the 3-4 heap data structure. The aim is to prove that the 3-4 heap, like its counter-part 2-3 heap, also supports n insert, n delete-min, and m decrease-key operations, in O(m + nlog n) time. Many performance tests were carried out during this research comparing the 3-4 heap against the 2-3 heap and for a narrow set of circumstances the 3-4 heap outperformed the 2-3 heap. The 2-3 heap has got a structure based on dimensions which are rigid using ternary linking and this path is made up of three nodes linked together to form a trunk, and the trunk is permitted to shrink by one. If further shrinkage is required then an adjustment is made by moving a few nodes from nearby positions to ensure the heaps rigid dimensions are retained. Should this no longer be the case, then the adjustment will trigger a make-up event, which propagates to higher dimensions, and requires amortised analysis. To aid amortised analysis, the trunk is given a measurement value called potential and this is the number of comparisons required to place each node into its correct position in ascending order using linear search. The divergence of the 3-4 heap from the 2-3 heap is that the trunk maximum is increased by one to four and is still permitted to shrink by one. This modified data structure will have a wide range of applications as the data storage mechanism used by graph algorithms such as Dijkstra's 'Single Source Shortest Path'.

No description available.

Heap leaching is a hydrometallurgical process used for the extraction of minerals within complex and typically low-grade ores. An important factor in the mineral dissolution process is the contact efficiency between the irrigation fluid (lixiviant) and the targeted mineral, which is influenced by both the solid and fluid properties of the system. One of the principal challenges related to the contact efficiency is preferential flow, cited to result in low extraction rates and in extreme cases, heap failure. Preferential flow reveals itself on two scales in drip irrigated heaps, referred to as the bed and solution scale. The bed scale takes a macro view of the heap and deals with uneven wetting profiles characterized by the presence of wet and dry sections. Linked to this is capillary suction effects which play an important role in the establishment of fluid flow profiles within the heap. The solution scale focuses on preferential flow behaviour in the wetted sections of the heap characterized by variations in the residence times of fluid elements. Such variations produce fast flowing, slow flowing and stagnant solution pools. Therefore, ideal solution flow behaviour in a heap result in uniform wetting at the bed scale and plug flow behaviour with similar fluid residence times at the solution scale. Though bed scale preferential flow can be visually observed, diagnosing symptoms at the solution scale typically requires the generation, analysis, and modelling of residence time distribution (RTD) curves. The main objectives of this study were to firstly explore the effects that important material and fluid properties have on the steady state fluid flow profiles in drip irrigated beds characteristic of those used in laboratory scale column leaching studies and quantified using step tracer tests. This is based on the underlying principle that the movement of inert tracer molecules within an irrigated bed at steady state is identical to the solution flow path within the bed. The second objective was to test the ability of nine empirical and semi-empirical solute transport models to adequately fit the generated flow profiles or RTD curves. The third was to compare the magnitudes of the quantified model parameters to ascertain the level of solution scale preferential flow in the different beds and determine the adequate level of model complexity needed to describe their flow profiles which facilitates identifying the controlling variables within the system. Properties of the loading material that were identified as potentially most impactful with respect to heap operations were: porosity, wettability, particle shape and size distribution. Therefore, four different materials with unique inherent characteristics were selected for this study: glass beads (GB - spherical and non-porous), glass shards (GS - irregularly shaped and non-porous), greywacke (GW - irregularly shaped, porous, and highly wettable) and malachite ore (MO - irregularly shaped, highly porous, low wettability and non-uniform composition). In terms of fluid properties, current models have already established a correlation between the concentration of dissolved chemical species within a fluid and its viscosity. This was relevant due to the variety of lixiviant compositions used in previous heap hydrology studies and the fact that the composition also varies with time within a reactive heap. To study the effects of this parameter on the establishment of flow profiles, glycerol was used as a viscosity modifier to formulate solutions with viscosities ranging from 0.8 to 2.2 cP, representative of the range experienced in heap leaching systems due to varying SO4 2- concentrations. The packed beds were characterized using their bulk densities, void age, total liquid holdups, total bed saturations, 24-hour drain-down moisture percentages, solution and tracer breakthrough times. Beds containing both narrow and mixed particle size fractions were tested. The nine solute transport models used for RTD modelling included three compartmental model configurations (CM-1, CM-2, CM-3) and the tanks-in-series (TIS) model, all empirical in nature. The five semi-empirical models selected were the advection-dispersion (AD), piston exchange (PE), piston exchange-diffusion variant (PE-D) and piston dispersion and exchange (PDE) models. A novel model formulation called the piston dispersion and exchange-diffusion variant (PDE-D) model was also coded and tested, which incorporated both the longitudinal dispersion coefficient as well as a diffusional flux mass transfer mechanism. The CM-2, AD and TIS were mono porosity models assuming all solution volumes within the beds were actively flowing which limited their ability to account for solution scale preferential flow. The CM-1, CM-3, PE, PE-D, PDE, PDE-D models were dual porous, accounting for the presence of either dead or stagnant solution volumes. The model parameters used to account for preferential flow in the RTD profiles included: the fraction of dead to total solution volume, dynamic to total saturation fraction, number of TIS, ratio of parallel continuously stirred tank volumes, longitudinal dispersion coefficient, overall mass transfer coefficient and maximum diffusional pore length. The cumulative RTD responses for the bed systems composed of narrow size fractions were noticeably impacted by particle size. These systems displayed symptoms of increased solution channelling behaviour at steady state, based on their relatively short tracer breakthrough times, as the average particle size was increased from ∼1 to 15 mm. The incorporation of semi-empirical models which could account for stagnant volumes. The main comparative modelling results across all systems studied showed that the PDE and PDE-D models were the top performers, based on a model fit analysis. This was due to their dual porous nature and relatively higher levels of complexity. The mono porosity models (CM-2, TIS and AD) performed the worst due to their inability to account for isolated and immobile liquid volumes. However, when 10 mm during agglomeration will aid in increasing the fraction of mobile (actively flowing) liquid within the heap due to the increased presence of macro voids. High levels of particle porosities (>2.5 m2/g) will also aid in this aspect. This is proposed to be due to greater void network connectivity with an increase in porosity facilitating better mass transfer. These insights were obtained through the analysis of experimentally generated data and model simulations. They have provided a better understanding of the movement of fluid molecules within drip irrigated beds, which is essential for improved leaching performance. Building on this, the next step is to consider the effects of scale up and reactive systems on both empirical and simulated data.

Programmers increasingly rely on managed languages (e.g. Java and C#) to develop applications faster and with fewer bugs. Managed languages encourage allocating objects in the heap and rely on automatic memory management (garbage collection) to reclaim objects the program can no longer access. With more objects in the heap, the heap encodes more program state than ever before and offers new opportunities for optimization and analysis. This dissertation shows how to efficiently leverage the managed runtime to perform dynamic heap analysis. Previous heap analysis approaches significantly slow down programs, require special hardware, and/or increase memory consumption by 75% or more. We presents two synergistic techniques—dynamic object sampling (DOS) and heap summarization (HSG)—that mine program state embedded in the heap efficiently enough to use in production and effectively enough to improve performance, find bugs, and increase program understanding. We use these techniques to address three problems: (1) Performance of managed language. Because some objects live for a long time, they incur disproportionate collection costs. We optimize these costs with dynamic pretenuring. Dynamic pretenuring uses DOS to accurately predict allocation site survival rates and uses these predictions to improve performance. (2) Finding bugs. Memory leaks in managed languages occur when a program inadvertently maintains references to objects that it no longer needs. Along with degrading performance and resulting in program crashes, memory leaks cause systematic heap growth. We introduce Cork which uses the simplest type of HSG, a class points-from summary graph (CPFG), to detect systematic heap growth. Cork quickly identifies growing data structures observed in three popular benchmarks (fop, jess, and jbb2000) while adding an average of only 2.3% to total time. Additionally, we use Cork to debug a reported memory leak in Eclipse. (3) Program understanding. For a long time, static analysis has sought to statically summarize the shape of dynamic data structures to aid in program verification and understanding. Unfortunately, it only works on small programs. We introduce ShapeUp which instead characterizes recursive data structures dynamically by discovering data structure shape and degree invariants at runtime. ShapeUp uses DOS and a class field-wise summary graph (CFSG) to track in- and out-degree invariants of data structure nodes. We show how ShapeUp automatically identifies recursive data structures and likely shape invariants. Finally, we monitor discovered shape invariants to detect when a data structure becomes malformed. In summary, this dissertation is the first to leverage the managed runtime to perform dynamic heap analysis both accurately and efficiently. Our results show that the heap contains an enormous amount of program state and that there is much potential for dynamically mining heap characteristics for optimization, debugging, and program understanding. / text