Records Added in August 2018
Records added in August 2018
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Showing records 1 to 25 of 45. [First] Page: 1 2 Last
Modeling the Dynamics of Human Liver Failure Post Liver Resection
Babita K. Verma, Pushpavanam Subramaniam, Rajanikanth Vadigepalli
August 28, 2018 (v1)
Keywords: cell death, Dynamic Modelling, liver failure, liver regeneration, liver resection, virtual patient
Liver resection is an important clinical intervention to treat liver disease. Following liver resection, patients exhibit a wide range of outcomes including normal recovery, suppressed recovery, or liver failure, depending on the regenerative capacity of the remnant liver. The objective of this work is to study the distinct patient outcomes post hepatectomy and determine the processes that are accountable for liver failure. Our model based approach shows that cell death is one of the important processes but not the sole controlling process responsible for liver failure. Additionally, our simulations showed wide variation in the timescale of liver failure that is consistent with the clinically observed timescales of post hepatectomy liver failure scenarios. Liver failure can take place either instantaneously or after a certain delay. We analyzed a virtual patient cohort and concluded that remnant liver fraction is a key regulator of the timescale of liver failure, with higher remnant li... [more]
Combining Petroleum Coke and Natural Gas for Efficient Liquid Fuels Production
Ikenna J Okeke, Thomas A Adams II
August 28, 2018 (v1)
This work explores the technical feasibility and economic profitability of converting petroleum coke (petcoke) and natural gas to liquid fuels via Fischer-Tropsch synthesis. Different petcoke conversion strategies were examined to determine the conversion pathway which can be competitive with current market prices with little or no adverse environmental impacts. Three main design approaches were considered: petcoke gasification only, combined petcoke gasification and natural gas reforming through traditional processing steps, and combined petcoke gasification and natural gas reforming by directly integrating the gasifier’s radiant cooler with the gas reformer. The designs investigated included scenarios with and without carbon capture and sequestration, and with and without CO2 emission tax penalties. The performance metrics considered included net present value, life cycle greenhouse gas emissions, and the cost of CO2 avoided. The design configuration that integrated natural gas refor... [more]
Modeling and simulation of an integrated steam reforming and nuclear heat system
Leila Hoseinzade, Thomas A Adams II
November 20, 2018 (v3)
Keywords: Carbonless heat, Dynamic Modelling, integrated systems, Steam methane reforming, Syngas
In this study, a dynamic and two-dimensional model for a steam methane reforming process integrated with nuclear heat production is developed. The model is based on first principles and considers the conservation of mass, momentum and energy within the system. The model is multi-scale, considering both bulk gas effects as well as spatial differences within the catalyst particles. Very few model parameters need to be fit based on the design specifications reported in the literature. The resulting model fits the reported design conditions of two separate pilot-scale studies (ranging from 0.4 to 10 MW heat transfer duty). A sensitivity analysis indicated that disturbances in the helium feed conditions significantly affect the system, but the overall system performance only changes slightly even for the large changes in the value of the most uncertain parameters.
An Integrated Mathematical Model of Cellular Cholesterol Biosynthesis and Lipoprotein Metabolism
Frances Pool, Peter K. Sweby, Marcus J. Tindall
August 28, 2018 (v1)
Keywords: ordinary differential equation, SREBP-2
Cholesterol regulation is an important aspect of human health. In this work we bring together and extend two recent mathematical models describing cholesterol biosynthesis and lipoprotein endocytosis to create an integrated model of lipoprotein metabolism in the context of a single hepatocyte. The integrated model includes a description of low density lipoprotein (LDL) receptor and cholesterol synthesis, delipidation of very low density lipoproteins (VLDLs) to LDLs and subsequent lipoprotein endocytosis. Model analysis shows that cholesterol biosynthesis produces the majority of intracellular cholesterol. The availability of free receptors does not greatly effect the concentration of intracellular cholesterol, but has a detrimental effect on extracellular VLDL and LDL levels. We test our model by considering its ability to reproduce the known biology of Familial Hypercholesterolaemia and statin therapy. In each case the model reproduces the known biological behaviour. Quantitative diff... [more]
Design and Implementation of an Optimal Travel Route Recommender System on Big Data for Tourists in Jeju
Lei Hang, Sang-Hun Kang, Wenquan Jin, Do-Hyeun Kim
August 28, 2018 (v1)
Keywords: association rule mining, mobile, route optimization, travel planning, travel route recommendation
A recommender system is currently applied in many different domains, seeking to provide users with recommendation services according to their personalized preferences to relieve rising online information congestion. As the number of mobile phone users is large and growing, mobile tourist guides have attracted considerable research interest in recent years. In this paper, we propose an optimal travel route recommender system by analyzing the data history of previous users. The open dataset used covers the travel data from thousands of mobile tourists who visited Jeju in a full year. Our approach is not only personalized to users’ preferences but also able to recommend a travel route rather than individual POIs (Points of Interest). An association rule mining-based approach, which takes into account contextual information (date, season and places already visited by previous users), is used to produce travel routes from the large dataset. Furthermore, to ensure the reasonability of the re... [more]
Dynamic Sequence Specific Constraint-Based Modeling of Cell-Free Protein Synthesis
David Dai, Nicholas Horvath, Jeffrey Varner
August 28, 2018 (v1)
Subject: Biosystems
Keywords: cell-free protein synthesis, dynamic constraint-based modeling, systems biology
Cell-free protein expression has emerged as an important approach in systems and synthetic biology, and a promising technology for personalized point of care medicine. Cell-free systems derived from crude whole cell extracts have shown remarkable utility as a protein synthesis technology. However, if cell-free platforms for on-demand biomanufacturing are to become a reality, the performance limits of these systems must be defined and optimized. Toward this goal, we modeled E. coli cell-free protein expression using a sequence specific dynamic constraint-based approach in which metabolite measurements were directly incorporated into the flux estimation problem. A cell-free metabolic network was constructed by removing growth associated reactions from the iAF1260 reconstruction of K-12 MG1655 E. coli. Sequence specific descriptions of transcription and translation processes were then added to this metabolic network to describe protein production. A linear programming problem was then sol... [more]
Experimental Study on the Reinforcement Mechanism of Segmented Split Grouting in a Soft Filling Medium
Zhipeng Li, Shucai Li, Haojie Liu, Qingsong Zhang, Yanan Liu
August 28, 2018 (v1)
Subject: Materials
Keywords: model experiment, reinforcement mechanism, rock-soil mechanics, segmented grouting, soft filling medium, split grouting
Subsection split grouting technology can effectively improve the grouting efficiency and homogeneity of grouting in a target reinforcement area. It is therefore necessary to clarify the reinforcement mechanism and characteristics of the soft filling medium under the condition of split grouting. A three-dimensional grouting simulation test of segmented split grouting in a soft filling medium was conducted. The distribution characteristics and thicknesses of the grouting veins were obtained under the condition of segmented grouting. The mechanical mechanism of segmented split grouting reinforcement, based on the distribution characteristics of different grouting veins, was revealed. After grouting, a uniaxial compression test and an indoor permeation test were conducted. Based on the method of the region-weighted average, the corresponding permeability coefficient and the elastic modulus of each splitting-compaction region were obtained. The quantitative relationship between the mechanic... [more]
Choosing the Optimal Multi-Point Iterative Method for the Colebrook Flow Friction Equation
Pavel Praks, Dejan Brkić
August 28, 2018 (v1)
Keywords: Colebrook equation, Colebrook–White, explicit approximations, hydraulic resistances, iterative methods, pipes, three-point methods, turbulent flow
The Colebrook equation is implicitly given in respect to the unknown flow friction factor λ; λ = ζ ( R e , ε * , λ ) which cannot be expressed explicitly in exact way without simplifications and use of approximate calculus. A common approach to solve it is through the Newton⁻Raphson iterative procedure or through the fixed-point iterative procedure. Both require in some cases, up to seven iterations. On the other hand, numerous more powerful iterative methods such as three- or two-point methods, etc. are available. The purpose is to choose optimal iterative method in order to solve the implicit Colebrook equation for flow friction accurately using the least possible number of iterations. The methods are thoroughly tested and those which require the least possible number of iterations to reach the accurate solution are identified. The most powerful three-point methods require, in the worst case, only two iterations to reach the final solution. The recommended representativ... [more]
Comparison of a Novel Miniaturized Screening Device with Büchi B290 Mini Spray-Dryer for the Development of Spray-Dried Solid Dispersions (SDSDs)
Aymeric Ousset, Joke Meeus, Florent Robin, Martin Alexander Schubert, Pascal Somville, Kalliopi Dodou
August 28, 2018 (v1)
Keywords: amorphous solid dispersions, downscaling, miniaturization, miscibility, Polymers, screening, spray-dryer
Spray-drying is an increasingly popular technology for the production of amorphous solid dispersions (ASDs) in the pharmaceutical industry that is used in the early evaluation and industrial production of formulations. Efficient screening of ASD in the earliest phase of drug development is therefore critical. A novel miniaturized atomization equipment for screening spray-dried solid dispersions (SDSDs) in early formulation and process development was developed. An in-depth comparison between the equipment/process parameters and performance of our novel screening device and a laboratory Büchi B290 mini spray-dryer was performed. Equipment qualification was conducted by comparing the particle/powder attributes, i.e., miscibility/solid state, residual solvent, and morphological properties of binary SDSDs of itraconazole prepared at both screening and laboratory scales. The operating mode of the miniaturized device was able to reproduce similar process conditions/parameters (e.g., outlet t... [more]
Modelling Nutrients and Organics Removal by Biological Slow Filtration in Micro-Polluted Water Source Treatment
Chengjin Zhang, Jian He, Zheng Zheng
August 28, 2018 (v1)
Keywords: biological slow filter, degradation mechanism, influencing factors, nutrients, organics
The biological slow filtration (BSF) system as a simple and efficient environmental technology has been widely applied in treatment of ‘micro-polluted’ water. At present, many related studies have focused on the removal efficiency of biological indicators (such as bacteria and viruses). However, there is less research on the removal performance of nutrients and organics in the BSF system. In this paper, we employed a lab-scale biological slow filter to study the removal efficiency and degradation mechanism of nutrients and organics. We proved through adsorption of filter layer at the early running stage and biodegradation at the later stage, the BSF system could achieve effective removal of NH₃-N, TN, TP, CODMn and turbidity and the corresponding removal rates are 83.65%, 42.45%, 42.94%, 60.41% and 83.55%, respectively. Furthermore, we also explored the influence of four main factors (filtration rate, filter depth, hydraulic head and temperature) and their interactions on removal rates... [more]
A Strain-Based Percolation Model and Triaxial Tests to Investigate the Evolution of Permeability and Critical Dilatancy Behavior of Coal
Dongjie Xue, Jie Zhou, Yintong Liu, Sishuai Zhang
August 28, 2018 (v1)
Keywords: CH4 seepage, deviatoric stress, enhanced permeability, mechanical behavior transition, strain-based percolation model, volumetric strain
Modeling the coupled evolution of strain and CH₄ seepage under conventional triaxial compression is the key to understanding enhanced permeability in coal. An abrupt transition of gas-stress coupled behavior at the dilatancy boundary is studied by the strain-based percolation model. Based on orthogonal experiments of triaxial stress with CH₄ seepage, a complete stress-strain relationship and the corresponding evolution of volumetric strain and permeability are obtained. At the dilatant boundary of volumetric strain, modeling of stress-dependent permeability is ineffective when considering the effective deviatoric stress influenced by confining pressure and pore pressure. The computed tomography (CT) analysis shows that coal can be a continuous medium of pore-based structure before the dilatant boundary, but a discontinuous medium of fracture-based structure. The multiscale pore structure geometry dominates the mechanical behavior transition and the sudden change in CH₄ seepage. By the... [more]
A Cybernetic Approach to Modeling Lipid Metabolism in Mammalian Cells
Lina Aboulmouna, Shakti Gupta, Mano R. Maurya, Frank T. DeVilbiss, Shankar Subramaniam, Doraiswami Ramkrishna
August 28, 2018 (v1)
Keywords: cybernetic modeling, lipids, metabolic objective functions, omics data, Optimization, prostaglandin metabolism
The goal-oriented control policies of cybernetic models have been used to predict metabolic phenomena such as the behavior of gene knockout strains, complex substrate uptake patterns, and dynamic metabolic flux distributions. Cybernetic theory builds on the principle that metabolic regulation is driven towards attaining goals that correspond to an organism’s survival or displaying a specific phenotype in response to a stimulus. Here, we have modeled the prostaglandin (PG) metabolism in mouse bone marrow derived macrophage (BMDM) cells stimulated by Kdo2-Lipid A (KLA) and adenosine triphosphate (ATP), using cybernetic control variables. Prostaglandins are a well characterized set of inflammatory lipids derived from arachidonic acid. The transcriptomic and lipidomic data for prostaglandin biosynthesis and conversion were obtained from the LIPID MAPS database. The model parameters were estimated using a two-step hybrid optimization approach. A genetic algorithm was used to determine the p... [more]
Preparation and Characterization of Polyaluminum Titanium Silicate and its Performance in the Treatment of Low-Turbidity Water
Lina Liao, Peng Zhang
August 28, 2018 (v1)
Subject: Materials
Keywords: coagulant, low turbidity, polyaluminum titanium silicate chloride, zeta potential
Using conventional coagulant, low turbidity water is difficult to achieve standard. This research uses aluminum chloride, titanium tetrachloride, and sodium silicate as raw materials for the preparation of polyaluminum titanium silicate chloride (PATC). PATC is used to treat low turbidity. The synthetic PATC showed the best coagulating effect in treated water under the following experimental conditions: Reaction temperature of 50 °C, and n(Ti)/n(Al), n(-OH)/n(Ti+Al), and n(Si)/n(Ti+Al) were 0.3, 0.2, and 1.0, respectively. The species distribution and the transformation of PATC showed that the interaction between titanium tetrachloride, sodium silicate, and the hydrolysate of Al influenced the morphology distribution of Al. Temperature and -OH greatly affected the distribution of Alb in PATC. The analysis of infrared spectra and X-ray diffraction indicated that both titanium tetrachloride and sodium silicate had complex chemical reactions with aluminum chloride. Si-O-Ti and Si-O-Al pro... [more]
Computational Molecular Modeling of Transport Processes in Nanoporous Membranes
Kevin R. Hinkle, Xiaoyu Wang, Xuehong Gu, Cynthia J. Jameson, Sohail Murad
August 28, 2018 (v1)
Keywords: ion-transport, membrane separations, molecular simulation
In this report we have discussed the important role of molecular modeling, especially the use of the molecular dynamics method, in investigating transport processes in nanoporous materials such as membranes. With the availability of high performance computers, molecular modeling can now be used to study rather complex systems at a fraction of the cost or time requirements of experimental studies. Molecular modeling techniques have the advantage of being able to access spatial and temporal resolution which are difficult to reach in experimental studies. For example, sub-Angstrom level spatial resolution is very accessible as is sub-femtosecond temporal resolution. Due to these advantages, simulation can play two important roles: Firstly because of the increased spatial and temporal resolution, it can help understand phenomena not well understood. As an example, we discuss the study of reverse osmosis processes. Before simulations were used it was thought the separation of water from sal... [more]
Deformation and Hydraulic Conductivity of Compacted Clay under Waste Differential Settlement
Sifa Xu, Cuifeng Li, Jizhuang Liu, Mengdan Bian, Weiwei Wei, Hao Zhang, Zhe Wang
August 28, 2018 (v1)
Subject: Materials
Keywords: bentonite-sand mixtures, crack, deformation, differential settlement, geogrid, hydraulic conductivity
Landfill is still the most important process to dispose of municipal solid waste in China, while landfill closure aims for pollution control, security control, and better land reuse. However, uneven settlement of landfill cover system is very likely to cause deformation and cracking. The objective of this paper is to examine the effects of geogrid reinforcement on the deformation behaviour and hydraulic conductivity of the bentonite-sand mixtures that are subjected to differential settlement. The laboratory model tests were performed on bentonite-sand mixtures with and without the inclusion of geogrid reinforcement. By maintaining the type and location of the geogrid within the liner systems as constant, the thickness of the bentonite-sand mixtures is varied. The performation of the liner systems with and without the inclusion of geogrid reinforcement was assessed by using jack to control differential settlement. Un-reinforced bentonite-sand mixtures of 100 mm and 200 mm thickness were... [more]
Technology for the Remediation of Water Pollution: A Review on the Fabrication of Metal Organic Frameworks
Yongning Bian, Nana Xiong, Guocheng Zhu
August 28, 2018 (v1)
Subject: Materials
Keywords: Adsorption, metal organic frameworks, remediation, water pollution
The ineffective control of the release of pollutants into water has led to serious water pollution. Compared with conditions in the past, the polluting components in aquatic environments have become increasingly complex. Some emerging substances have led to a new threat to the safety of water. Therefore, developing cost-effective technologies for the remediation of water pollution is urgently needed. Adsorption has been considered the most effective operational unit in water treatment processes and thus adsorption materials have gained wide attention. Among them, metal organic frameworks (denoted as MOFs) have been rapidly developed in recent years due to their unique physicochemical performance. They are characterized by larger porosity and larger specific surface area, easier pore structure designing, and comfortable structural modification. In many fields such as adsorption, separation, storage, and transportation, MOFs show a better performance than conventional adsorption material... [more]
Effect of Particle Size on Carbon Nanotube Aggregates Behavior in Dilute Phase of a Fluidized Bed
Sung Won Kim
August 28, 2018 (v1)
Subject: Materials
Keywords: aggregates, carbon nanotube, fluidized bed, laser sheet technique, particle size
Fluidized bed reactors have been increasingly applied for mass production of Carbon Nanotube (CNT) using catalytic chemical vapor deposition technology. Effect of particle size (dp = 131 μm and 220 μm) on fluidization characteristics and aggregation behavior of the CNT particles have been determined in a fluidized bed for its design and scale-up. The CNT aggregation properties such as size and shape were measured in the dilute phase of a fluidized bed (0.15 m-ID × 2.6 m high) by the laser sheet technique for the visualization. Two CNT particle beds showed different tendency in variations of the aggregates factors with gas velocity due to differences in factors contributing to the aggregate formation. The CNT particles with a larger mean size presented as relatively larger in the aggregate size than the smaller CNT particles at given gas velocities. The aggregates from the large CNT particles showed a sharp increase in the aspect ratio and rapid decrease in the roundness and the solidit... [more]
A Coupled Thermal-Hydraulic-Mechanical Nonlinear Model for Fault Water Inrush
Weitao Liu, Jiyuan Zhao, Ruiai Nie, Yuben Liu, Yanhui Du
August 28, 2018 (v1)
Keywords: coupled THM model, fault water inrush, nonlinear flow in fractured porous media, numerical model, warning levels of fault water inrush
A coupled thermal-nonlinear hydraulic-mechanical (THM) model for fault water inrush was carried out in this paper to study the water-rock-temperature interactions and predict the fault water inrush. First, the governing equations of the coupled THM model were established by coupling the particle transport equation, nonlinear flow equation, mechanical equation, and the heat transfer equation. Second, by setting different boundary conditions, the mechanical model, nonlinear hydraulic-mechanical (HM) coupling model, and the thermal-nonlinear hydraulic-mechanical (THM) coupling model were established, respectively. Finally, a numerical simulation of these models was established by using COMSOL Multiphysics. Results indicate that the nonlinear water flow equation could describe the nonlinear water flow process in the fractured zone of the fault. The mining stress and the water velocity had a great influence on the temperature of the fault zone. The temperature change of the fault zone can r... [more]
Effects of Pulse Interval and Dosing Flux on Cells Varying the Relative Velocity of Micro Droplets and Culture Solution
Zhanwei Wang, Kun Liu, Jiuxin Ning, Shulei Chen, Ming Hao, Dongyang Wang, Qi Mei, Yaoshuai Ba, Dechun Ba
August 28, 2018 (v1)
Subject: Materials
Keywords: cell dosing, convective diffusion, interdiffusion, microdroplet, numerical simulation
Microdroplet dosing to cell on a chip could meet the demand of narrow diffusion distance, controllable pulse dosing and less impact to cells. In this work, we studied the diffusion process of microdroplet cell pulse dosing in the three-layer sandwich structure of PDMS (polydimethylsiloxane)/PCTE (polycarbonate) microporous membrane/PDMS chip. The mathematical model is established to solve the diffusion process and the process of rhodamine transfer to micro-traps is simulated. The rhodamine mass fraction distribution, pressure field and velocity field around the microdroplet and cell surfaces are analyzed for further study of interdiffusion and convective diffusion effect. The cell pulse dosing time and drug delivery efficiency could be controlled by adjusting microdroplet and culture solution velocity without impairing cells at micro-traps. Furthermore, the accuracy and controllability of the cell dosing pulse time and maximum drug mass fraction on cell surfaces are achieved and the dr... [more]
Input Shaping Predictive Functional Control for Different Types of Challenging Dynamics Processes
Muhammad Abdullah, John Anthony Rossiter
August 28, 2018 (v1)
Keywords: input shaping, integrating, predictive control, underdamped, unstable
Predictive functional control (PFC) is a fast and effective controller that is widely used for processes with simple dynamics. This paper proposes some techniques for improving its reliability when applied to systems with more challenging dynamics, such as those with open-loop unstable poles, oscillatory modes, or integrating modes. One historical proposal considered is to eliminate or cancel the undesirable poles via input shaping of the predictions, but this approach is shown to sometimes result in relatively poor performance. Consequently, this paper proposes to shape these poles, rather than cancelling them, to further enhance the tuning, feasibility, and stability properties of PFC. The proposed modification is analysed and evaluated on several numerical examples and also a hardware application.
A New Concept of Stirred Multiphase Reactor Using a Stationary Catalytic Foam
Nassima Benamara, Didier Assoua, Louis Jaffeux, Laurent Vanoye, Florica Simescu-Lazar, Marie-Line Zanota, Frédéric Bornette, Valérie Meille, Isabelle Pitault
August 28, 2018 (v1)
Keywords: basket reactor, foam, mass transfer, structured reactors
Developing new stirred gas⁻liquid⁻solid reactors with high mass transfer capabilities is still a challenge. In this publication, we present a new concept of multiphase reactor using a stationary catalytic foam and a gas-inducing impeller. The gas⁻liquid (GL) and liquid⁻solid (LS) mass transfer rates in this reactor were compared to a stirred reactor with basket filled with beads. Batch absorption of hydrogen and measurement of α-methylstyrene hydrogenation rate on Pd/Al2O3 catalyst were used to evaluate kGLaGL coefficients and kLS coefficients, respectively. With similar LS transfer rates to the basket-reactor and much higher GL transfer rates, the new reactor reveals a very promising tool for intrinsic kinetics investigations.
Flotation in Water and Wastewater Treatment
George Z. Kyzas, Kostas A. Matis
August 28, 2018 (v1)
Keywords: Biomass, dispersed-air flotation, metals, particles, separation
Flotation constitutes a separation process that originated from mineral processing. Nowadays, wider applications have been found and compared to flotation for water and wastewater treatment. Stress in the present review paper was mainly applied to heavy metal ions recovery by flotation and the respective mechanism followed, being either ion, precipitate, or sorptive flotation. In the latter case, the use of adsorbents is included (such as powdered activated carbon, zeolites, and goethite), as well as various biosorbents. The flotation of the following metals was reviewed: copper, zinc, nickel, lead, iron, chromium, arsenic, gold, and others. The bubble generation method could be applied for typical dispersed-air flotation column, electroflotation, or dissolved-air flotation; the latter being the most appropriate established technique in water treatment. The role of particle size (for example, studying flotation of salt-type mineral fines) was also examined.
Dynamic Optimization of a Subcritical Steam Power Plant Under Time-Varying Power Load
Chen Chen, George M. Bollas
August 28, 2018 (v1)
Subject: Optimization
Keywords: dynamic optimization, dynamic simulation, power plants, supervisory control
The increasing variability in power plant load in response to a wildly uncertain electricity market and the need to to mitigate CO₂ emissions, lead power plant operators to explore advanced options for efficiency optimization. Model-based, system-scale dynamic simulation and optimization are useful tools in this effort and are the subjects of the work presented here. In prior work, a dynamic model validated against steady-state data from a 605 MW subcritical power plant was presented. This power plant model was used as a test-bed for dynamic simulations, in which the coal load was regulated to satisfy a varying power demand. Plant-level control regulated the plant load to match an anticipated trajectory of the power demand. The efficiency of the power plant’s operation at varying loads was optimized through a supervisory control architecture that performs set point optimization on the regulatory controllers. Dynamic optimization problems were formulated to search for optimal time-varyi... [more]
Numerical Simulation of Hydraulic Fracture Propagation in Coal Seams with Discontinuous Natural Fracture Networks
Shen Wang, Huamin Li, Dongyin Li
August 28, 2018 (v1)
Keywords: coal seams, cohesive element method, discontinuous natural fracture, fracture propagation, hydraulic fracture network, secondary fracture
To investigate the mechanism of hydraulic fracture propagation in coal seams with discontinuous natural fractures, an innovative finite element meshing scheme for modeling hydraulic fracturing was proposed. Hydraulic fracture propagation and interaction with discontinuous natural fracture networks in coal seams were modeled based on the cohesive element method. The hydraulic fracture network characteristics, the growth process of the secondary hydraulic fractures, the pore pressure distribution and the variation of bottomhole pressure were analyzed. The improved cohesive element method, which considers the leak-off and seepage behaviors of fracturing liquid, is capable of modeling hydraulic fracturing in naturally fractured formations. The results indicate that under high stress difference conditions, the hydraulic fracture network is spindle-shaped, and shows a multi-level branch structure. The ratio of secondary fracture total length to main fracture total length was 2.11~3.62, sugge... [more]
Separation of Ag(I) by Ion Exchange and Cementation from a Raffinate Containing Ag(I), Ni(II) and Zn(II) and Traces of Cu(II) and Sn(II)
Wei Dong Xing, Man Seung Lee, Seung Hoon Choi
August 28, 2018 (v1)
Keywords: cementation, copper sheet, ion exchange, silver, silver particles
Ion exchange and cementation experiments were done to separate silver(I) from a raffinate containing silver(I), nickel(II), and zinc(II) and small amounts of copper(II) and tin(II). The raffinate resulted from the recovery of gold(III), tin(II) and copper(II) by solvent extraction from a leaching solution of anode slime. Ion exchange with anionic resins was not effective in separating silver(I) because tin(II) and zinc(II) were selectively adsorbed into the anionic resins. It was possible to separate silver(I) by cementation with copper sheet. Treatment of the cemented silver with nitric acid solution increased the purity of silver(I) in the solution from 50.9% to 99.99%. Adjusting the pH of the AgNO₃ solution to higher than 6, followed by adding ascorbic acid as a reducing agent, led to the synthesis of silver particles with micron size.
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