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Records Added in August 2018
Records added in August 2018
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Showing records 26 to 45 of 45. [First] Page: 1 2 Last
A High-Order Numerical Manifold Method for Darcy Flow in Heterogeneous Porous Media
Lingfeng Zhou, Yuan Wang, Di Feng
August 28, 2018 (v1)
Keywords: Darcy flow, heterogeneity, high-order, numerical manifold method, refraction law
One major challenge in modeling Darcy flow in heterogeneous porous media is simulating the material interfaces accurately. To overcome this defect, the refraction law is fully introduced into the numerical manifold method (NMM) as an a posteriori condition. To achieve a better accuracy of the Darcy velocity and continuous nodal velocity, a high-order weight function with a continuous nodal gradient is adopted. NMM is an advanced method with two independent cover systems, which can easily solve both continuous and discontinuous problems in a unified form. Moreover, a regular mathematical mesh, independent of the physical domain, is used in the NMM model. Compared to the conforming mesh of other numerical methods, it is more efficient and flexible. A number of numerical examples were simulated by the new NMM model, comparing the results with the original NMM model and the analytical solutions. Thereby, it is proven that the proposed method is accurate, efficient, and robust for modeling... [more]
Experimental Study on the Creep Characteristics of Coal Measures Sandstone under Seepage Action
Ziheng Sha, Hai Pu, Ming Li, Lili Cao, Ding Liu, Hongyang Ni, Jingfeng Lu
August 28, 2018 (v1)
Subject: Materials
Keywords: coal measures sandstone, creep characteristics, microscopic morphology, seepage pressure, seepage-creep
The seepage action of underground water accelerates the deformation of roadway surrounding rock in deep mines. Therefore, the study of creep characteristics of surrounding rock under seepage action is the basis for the stability control of roadway surrounding rock in deep water-rich areas. In this paper, a seepage-creep coupling test system for complete rock samples was established. Combined with a scanning electron microscopy (SEM) test system, the seepage-creep law of coal measures sandstone and the damage mechanism were revealed. The study results showed that the maximum creep deformation of sandstone under natural and saturation state decreased gradually with the increase of confining pressure, and the maximum creep deformation under saturation state was greater than the corresponding value under natural state when the confining pressure was same. When the confining pressure was constant, the creep deformation, the constant creep deformation rate and the accelerated creep deformati... [more]
Numerical Simulation on the Dynamic Characteristics of a Tremendous Debris Flow in Sichuan, China
Yulong Chen, Zhenfeng Qiu, Bo Li, Zongji Yang
August 28, 2018 (v1)
Keywords: debris flow, debris-resisting barriers, dynamic characteristics, numerical analysis
The mega debris flow that occurred on 13 August 2010 in Zoumaling Valley in Mianzhu County, China has done great damage to the local inhabitants, as well as to the re-construction projects in the quake-hit areas. Moreover, it is of high possibility that a secondary disaster would reappear and result in worse consequences. In order to maximize risk reduction of this problem, the local government planned to construct seven debris-resisting barriers across each ditch for mitigation of debris flow hazards in the future. In this paper, the numerical simulation fields of flow velocity, pressure, and mud depth of the Zoumaling debris flow had been computed by using finite volume method software based on computational fluid dynamics (CFD). The Bingham fluid was chosen as the constitutive model of this debris flow. The debris flow geometry model was a 3D model. The initial conditions, boundary conditions, control equations, and parameters were determined and adjusted by the actual conditions an... [more]
Fabrication of New Liquid Crystal Device Using Layer-by-Layer Thin Film Process
Gitae Moon, Wonjun Jang, Intae Son, Hyun A. Cho, Yong Tae Park, Jun Hyup Lee
August 28, 2018 (v1)
Subject: Materials
Keywords: electrode, layer-by-layer, liquid crystal device, thin film
Indium tin oxide (ITO) transparent electrodes are troubled with high cost and poor mechanical stability. In this study, layer-by-layer (LBL)-processed thin films with single-walled carbon nanotubes (SWNTs) exhibited high transparency and electrical conductivity as a candidate for ITO replacement. The repetitive deposition of polycations and stabilized SWNTs with a negative surfactant exhibits sufficiently linear film growth and high optoelectronic performance to be used as transparent electrodes for vertically aligned (VA) liquid crystal display (LCD) cells. The LC molecules were uniformly aligned on the all of the prepared LBL electrodes. VA LCD cells with SWNT LBL electrodes exhibited voltage-transmittance (V-T) characteristics similar to those with the conventional ITO electrodes. Although the response speeds were slower than the LCD cell with the ITO electrode, as the SWNT layers increased, the display performance was closer to the LCD cells with conventional ITO electrode. This wo... [more]
Effect of Pore Fluid Pressure on the Normal Deformation of a Matched Granite Joint
Qiang Zhang, Xiaochun Li, Bing Bai, Shaobin Hu, Lu Shi
August 28, 2018 (v1)
Subject: Materials
Keywords: constitutive model, effective stress, fracture closure, hydro-mechanical coupling, laboratory experiment, pore pressure
The influence of pore fluid pressure on the normal deformation behaviors of joints is vital for understanding the interaction between hydraulic and mechanical processes of joints. The effect of pore fluid pressure on the normal deformation of a granite matched joint was investigated by laboratory experiments. Experimental results indicate pore fluid pressure significantly affects the normal deformation of jointed sample, and the relative normal deformation of jointed sample during fluid injection consists of the opening of the joint and the dilation of host rock. The action of pore fluid pressure on the joint follows the Terzaghi’s effective stress law. The normal deformation of the joint can be well quantitated by the generalized exponential model. The relative normal deformation of host rock during fluid injection would have a linear relationship with pore fluid pressure, and if affected by gas is more pronounced than water.
GEKKO Optimization Suite
Logan D. R. Beal, Daniel C. Hill, R. Abraham Martin, John D. Hedengren
August 28, 2018 (v1)
Subject: Optimization
Keywords: algebraic modeling language, dynamic optimization, Model Predictive Control, moving horizon estimation
This paper introduces GEKKO as an optimization suite for Python. GEKKO specializes in dynamic optimization problems for mixed-integer, nonlinear, and differential algebraic equations (DAE) problems. By blending the approaches of typical algebraic modeling languages (AML) and optimal control packages, GEKKO greatly facilitates the development and application of tools such as nonlinear model predicative control (NMPC), real-time optimization (RTO), moving horizon estimation (MHE), and dynamic simulation. GEKKO is an object-oriented Python library that offers model construction, analysis tools, and visualization of simulation and optimization. In a single package, GEKKO provides model reduction, an object-oriented library for data reconciliation/model predictive control, and integrated problem construction/solution/visualization. This paper introduces the GEKKO Optimization Suite, presents GEKKO’s approach and unique place among AMLs and optimal control packages, and cites several example... [more]
Comparison between Two Solid-Liquid Extraction Methods for the Recovery of Steviol Glycosides from Dried Stevia Leaves Applying a Numerical Approach
Monica Gallo, Andrea Formato, Gaetano Formato, Daniele Naviglio
August 28, 2018 (v1)
Keywords: maceration, mathematical modeling, rebaudioside A, RSLDE, steviol glycosides, stevioside
Stevia rebaudiana Bertoni is a perennial shrub belonging to the Asteraceae family. The leaves contain a mixture of steviol glycosides with extraordinary sweetening properties, among which the most important are stevioside and rebaudioside A. These components have a high sweetening power, which is about 300 times that of sucrose, and a negligible calorie content. However, their extraction and purification are not easy. In this paper, the extraction technique under cyclic pressure, known as rapid solid-liquid dynamic extraction (RSLDE), was compared using a Naviglio extractor (NE) with conventional maceration. The aim was to identify an efficient and economically viable method for obtaining high amounts of steviol glycosides in a short time. Furthermore, a numerical model was set up for the solid-liquid extraction process of value-added compounds from natural sources. Several parameters must be evaluated in relation to the characteristics of the parts of the plant subjected to extraction... [more]
Coal Anisotropic Sorption and Permeability: An Experimental Study
Yulong Chen, Xuelong Li, Bo Li
August 28, 2018 (v1)
Subject: Materials
Keywords: adsorption–desorption, anisotropy, bedding plane orientation, Coal, gas
Knowledge of the bedding plane properties of coal seams is essential for the coalbed gas production because of their great influence on the inner flow characteristics and sorption features of gas and water. In this study, an experimental study on the anisotropic gas adsorption⁻desorption and permeability of coal is presented. The results show that during the adsorption⁻desorption process, an increase in the bedding plane angle of the specimen expands the length and area of the contact surface, thereby increasing the speed and quantity of adsorption and desorption. With an increase in the bedding angle, the number of pores and cracks was found to increase together with the volumetric strain. The evolution of permeability of coal heavily depended on stress⁻strain stages. The permeability decreased with the increase of stress at the initial compaction and elastic deformation stages, while it increased with the increase of stress at the stages of strain-hardening, softening and residual st... [more]
Underground Risk Index Assessment and Prediction Using a Simplified Hierarchical Fuzzy Logic Model and Kalman Filter
Muhammad Fayaz, Israr Ullah, Do-Hyeun Kim
August 28, 2018 (v1)
Keywords: fuzzy inference system, hierarchical fuzzy logic (HFL), membership functions (MFs), risk assessment, simplified hierarchical fuzzy logic (SHFL), underground risk
Normally, most of the accidents that occur in underground facilities are not instantaneous; rather, hazards build up gradually behind the scenes and are invisible due to the inherent structure of these facilities. An efficient inference system is highly desirable to monitor these facilities to avoid such accidents beforehand. A fuzzy inference system is a significant risk assessment method, but there are three critical challenges associated with fuzzy inference-based systems, i.e., rules determination, membership functions (MFs) distribution determination, and rules reduction to deal with the problem of dimensionality. In this paper, a simplified hierarchical fuzzy logic (SHFL) model has been suggested to assess underground risk while addressing the associated challenges. For rule determination, two new rule-designing and determination methods are introduced, namely average rules-based (ARB) and max rules-based (MRB). To determine efficient membership functions (MFs), a module named th... [more]
The Role of Immune Response in Optimal HIV Treatment Interventions
Hernán Darío Toro-Zapata, Angélica Caicedo-Casso, Sunmi Lee
August 28, 2018 (v1)
Subject: Biosystems
Keywords: anti-retroviral treatment, cytotoxic immune response, HIV transmission dynamics within a host, optimal control theory
A mathematical model for the transmission dynamics of human immunodeficiency virus (HIV) within a host is developed. Our model focuses on the roles of immune response cells or cytotoxic lymphocytes (CTLs). The model includes active and inactive cytotoxic immune cells. The basic reproduction number and the global stability of the virus free equilibrium is carried out. The model is modified to include anti-retroviral treatment interventions and the controlled reproduction number is explored. Their effects on the HIV infection dynamics are investigated. Two different disease stage scenarios are assessed: early-stage and advanced-stage of the disease. Furthermore, optimal control theory is employed to enhance healthy CD4+ T cells, active cytotoxic immune cells and minimize the total cost of anti-retroviral treatment interventions. Two different anti-retroviral treatment interventions (RTI and PI) are incorporated. The results highlight the key roles of cytotoxic immune response in the HIV... [more]
Experimental Study on the Damage of Granite by Acoustic Emission after Cyclic Heating and Cooling with Circulating Water
Dong Zhu, Hongwen Jing, Qian Yin, Guansheng Han
August 28, 2018 (v1)
Subject: Materials
Keywords: acoustic emission, cyclic heating and cooling, damage, failure mode, physical and mechanical parameters
Hot dry rock is developed by injecting cold water into high-temperature rock mass. At the same time, cold water is heated in contact with the rock mass. With the continuous influx of cold water, the surrounding rock will undergo a rapid cooling process, which results in several cycles of heating and cooling. However, there is little research on the influence of cycles of heating and cooling with circulating water on the mechanical properties of rock, which is of great importance to the stability of rock mass engineering in the process of energy development. In this paper, the effects of cyclic heating and cooling with circulating water on the damage of granite are studied using uniaxial compressive, Brazilian and acoustic emission (AE) tests. The results show that heat treatment temperature and number of cycles have important effects on the mechanical properties of granite as follows: (1) at the same treatment temperature, an increase in the number of cycles means that the distribution... [more]
Sequential Parameter Estimation for Mammalian Cell Model Based on In Silico Design of Experiments
Zhenyu Wang, Hana Sheikh, Kyongbum Lee, Christos Georgakis
August 28, 2018 (v1)
Subject: Biosystems
Keywords: Design of Experiments, Mammalian Cell Culture, parameter estimation, Pharmaceutical Processes, sensitivity analysis
Due to the complicated metabolism of mammalian cells, the corresponding dynamic mathematical models usually consist of large sets of differential and algebraic equations with a large number of parameters to be estimated. On the other hand, the measured data for estimating the model parameters are limited. Consequently, the parameter estimates may converge to a local minimum far from the optimal ones, especially when the initial guesses of the parameter values are poor. The methodology presented in this paper provides a systematic way for estimating parameters sequentially that generates better initial guesses for parameter estimation and improves the accuracy of the obtained metabolic model. The model parameters are first classified into four subsets of decreasing importance, based on the sensitivity of the model’s predictions on the parameters’ assumed values. The parameters in the most sensitive subset, typically a small fraction of the total, are estimated first. When estimating the... [more]
Experimental Study of the Microstructural Evolution of Glauberite and Its Weakening Mechanism under the Effect of Thermal-Hydrological-Chemical Coupling
Shuzhao Chen, Donghua Zhang, Tao Shang, Tao Meng
August 28, 2018 (v1)
Subject: Materials
Keywords: brine concentration, gas, glauberite cavern for storing oil &, micro-CT, microstructure, temperature, thermal-hydrological-chemical interactions
The microstructures of rock gradually evolve with changes in the external environment. This study focused on the microstructure evolution of glauberite and its weakening mechanism under different leaching conditions. The porosity were used as a characteristic index to study the effect of brine temperature and concentration on crack initiation and propagation in glauberite. The research subjects were specimens of ϕ3 × 10 mm cylindrical glauberite core, obtained from a bedded salt deposit buried more than 1000 m underground in the Yunying salt formation, China. The results showed that when the specimens were immersed in solution at low temperature, due to hydration impurities, cracks appeared spontaneously at the centre of the disc and the solution then penetrated the specimens via these cracks and dissolved the minerals around the crack lines. However, with an increase of temperature, the dissolution rate increased greatly, and crack nucleation and dissolved regions appeared simultaneou... [more]
Alternatives for Chemical and Biochemical Lignin Valorization: Hot Topics from a Bibliometric Analysis of the Research Published During the 2000⁻2016 Period
Ricardo Abejón, Heriberto Pérez-Acebo, Leonardo Clavijo
August 28, 2018 (v1)
Subject: Biosystems
Keywords: bibliometric analysis, lignin uses, lignin valorization, lignocellulosic biomass, research trends
A complete bibliometric analysis of the Scopus database was performed to identify the research trends related to lignin valorization from 2000 to 2016. The results from this analysis revealed an exponentially increasing number of publications and a high relevance of interdisciplinary collaboration. The simultaneous valorization of the three main components of lignocellulosic biomass (cellulose, hemicellulose, and lignin) has been revealed as a key aspect and optimal pretreatment is required for the subsequent lignin valorization. Research covers the determination of the lignin structure, isolation, and characterization; depolymerization by thermal and thermochemical methods; chemical, biochemical and biological conversion of depolymerized lignin; and lignin applications. Most methods for lignin depolymerization are focused on the selective cleavage of the β-O-4 linkage. Although many depolymerization methods have been developed, depolymerization with sodium hydroxide is the dominant pr... [more]
Modelling and Simulation of Biochemical Processes Using Petri Nets
Safae Cherdal, Salma Mouline
August 28, 2018 (v1)
Subject: Biosystems
Keywords: biochemical processes, diseases, HFPN, metabolic pathway, Methionine cycle, Petri nets, Simulation
Systems composed of many components which interact with each other and lead to unpredictable global behaviour, are considered as complex systems. In a biological context, complex systems represent living systems composed of a large number of interacting elements. In order to study these systems, a precise mathematical modelling was typically used in this context. However, this modelling has limitations in the structural understanding and the behavioural study. In this sense, formal computational modelling is an approach that allows to model and to simulate dynamical properties of these particular systems. In this paper, we use Hybrid Functional Petri Net (HFPN), a Petri net extension dedicated to study and verify biopathways, to model and study the Methionine metabolic pathway. Methionine and its derivatives play significant roles in human bodies. We propose a set of simulations for the purpose of studying and analysing the Methionine pathway’s behaviour. Our simulation results have sh... [more]
Supply Chain Optimization of Flare-Gas-To-Butanol Processes in Alberta
Leila Hoseinzade, Thomas A Adams II
August 15, 2018 (v1)
Subject: Optimization
Keywords: Portable technology, Supply chain optimization, Sustainability
In this work, the economic feasibility of combining a novel portable gas-to-methanol process with a novel methanol-to-butanol process is examined. The gas-to-methanol process converts waste flare gas into methanol using a series of truck-mounted devices deployed at oil production wellheads. The methanol-to-butanol process uses a new proprietary catalyst which produces butanol via a diketene intermediate at a large centralized facility. The goal of this work is to identify the best ways of commercializing this technology in Alberta. To do this, a supply chain optimization model is formulated which considers specifically how many gas-to-methanol trucks should be used and where specifically in Alberta they should be deployed, the specific suppliers of CO2 to use, where the location of the central methanol-to-butanol facility should be chosen, and the costs of transportation of materials between locations. The model framework also considers the possibility of getting methanol in full or in... [more]
Dynamic modeling of the integrated methane reforming and nuclear heat systems
Leila Hoseinzade, Thomas A Adams II
August 15, 2018 (v1)
Keywords: Carbonless Heat, Dynamic Modelling, Methane Reforming, Process integration
In this study, a dynamic and two-dimensional model for a steam methane reforming process integrated with nuclear heat production was developed. The model is based on first principals and considers the conservation of mass, momentum and energy within the system. Very few model parameter needed to be fit based on the experimental data reported in the literature. Using the fitted model and existing data, an industrial scale design for the integrated steam reforming and nuclear heat process is proposed. The system performance was analyzed by studying the dynamic behaviour of the key variables of the system. It has been shown that the methane conversion in the SMR tubes are generally lower than conventional reforming processes due to the low temperature of the gas flows in the shell side. Several options were investigated to increase the conversion of the methane in the SMR tubes, we found that combining steam reforming with dry reforming processes together can provide significant improveme... [more]
Combining Biomass, Natural Gas, Carbonless Heat to produce liquid fuels
Leila Hoseinzade, Thomas A Adams II
August 15, 2018 (v1)
Keywords: Biomass, Carbonless Heat, Natural Gas, Polygeneration
In this study, a new Biomass-Gas-Nuclear heat-To-Liquid fuel (BGNTL) process is presented which uses high-temperature nuclear heat as the heat source for steam methane reforming (SMR). This process co-produces liquid fuels (Fischer-Tropsch liquids, methanol and DME) and power. The BGNTL process was simulated using a combination of different software packages including gPROMS, MATLAB, ProMax, and Aspen Plus. This included the use of a rigorous multi-scale model for the nuclear-heat-powered SMR reactor which was developed in a prior work in gPROMS. Energy efficiency and cradle-to-grave life cycle inventory and life-cycle impact analyses of greenhouse gas (GHG) emissions were accomplished to analyze the environmental impacts of the BGNTL system. Plant performance was compared with a base case Biomass-Gas-To-Liquid (BGTL) process at the same size. In both processes, a carbon capture and storage (CCS) option is considered. It has been found that both processes result in negative total life... [more]
Aspen Plus Simulation of Biomass-Gas-and-Nuclear-To-Liquids (BGNTL) Processes (Using CuCl Route)
James Alexander Scott, Thomas Alan Adams II
August 7, 2018 (v1)
These are Aspen Plus simulation files for a Biomass-Gas-and-Nuclear-To-Liquids chemical plant (a conceptional design), which uses the Copper-Chloride route for hydrogen production. This is a part of a larger work (see linked LAPSE record for pre-print and associated publication in Canadian J Chem Eng). Process sections and major units in this simulation include: Gasification, Integrated-Gasification-Methane-Reforming, Pre-Reforming, Water Gas Shift, Autothermal Reforming, Syngas Blending and Upgrading, Solid Oxide Fuel Cell power islands, Fischer-Tropsch Synthesis, Methanol Synthesis, Dimethyl Ether Synthesis, Heat Recovery and Steam Generation, CO2 Compression for Sequestration, Cooling Towers, and various auxiliary units for heat and pressure management. See the linked work for a detailed description of the model.
Biomass-Gas-and-Nuclear-To-Liquids (BGNTL) Processes Part I: Model Development and Simulation
James Alexander Scott, Thomas Alan Adams II
August 7, 2018 (v1)
New polygeneration processes for the co-production of liquid fuels (Fischer-Tropsch liquids, methanol, and dimethyl ether) and electricity are presented. The processes use a combination of biomass, natural gas, and nuclear energy as primary energy feeds. Chemical process models were created and used to simulate candidate versions of the process, using combinations of models ranging from complex multi- scale models to standard process flowsheet models. The simulation results are presented for an Ontario, Canada case study to obtain key metrics such as efficiency and product conversions. Sample Aspen Plus files are provided in the supplementary material to be used by others.
Showing records 26 to 45 of 45. [First] Page: 1 2 Last
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