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Processes, Volume 6, Issue 8 (August 2018)

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Open AccessFeature PaperArticle An Integrated Mathematical Model of Cellular Cholesterol Biosynthesis and Lipoprotein Metabolism
Processes 2018, 6(8), 134; https://doi.org/10.3390/pr6080134
Received: 29 June 2018 / Revised: 8 August 2018 / Accepted: 10 August 2018 / Published: 18 August 2018
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Abstract
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
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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 differences in response to statin therapy are discussed in the context of the need to extend the work to a more in vivo setting via the incorporation of more dietary lipoprotein related processes and the need for further testing and parameterisation of in silico models of lipoprotein metabolism. Full article
(This article belongs to the Special Issue Methods in Computational Biology)
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Open AccessArticle Design and Implementation of an Optimal Travel Route Recommender System on Big Data for Tourists in Jeju
Processes 2018, 6(8), 133; https://doi.org/10.3390/pr6080133
Received: 24 July 2018 / Revised: 7 August 2018 / Accepted: 8 August 2018 / Published: 17 August 2018
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Abstract
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
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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 recommendation, a genetic algorithm optimization approach is proposed to find the optimal route among them. Finally, a mobile tourist case study is implemented in order to verify the feasibility and applicability of the proposed system. This application embeds a graphic map for plotting the travel route and provides detailed information of each travel spot as well. The results of this work indicate that the proposed system has great potential for travel planning preparation for mobile users. Full article
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Open AccessFeature PaperArticle Dynamic Sequence Specific Constraint-Based Modeling of Cell-Free Protein Synthesis
Processes 2018, 6(8), 132; https://doi.org/10.3390/pr6080132
Received: 8 June 2018 / Revised: 7 August 2018 / Accepted: 9 August 2018 / Published: 17 August 2018
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Abstract
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
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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 solved over short time intervals to estimate metabolic fluxes through the augmented cell-free network, subject to material balances, time rate of change and metabolite measurement constraints. The approach captured the biphasic cell-free production of a model protein, chloramphenicol acetyltransferase. Flux variability analysis suggested that cell-free metabolism was potentially robust; for example, the rate of protein production could be met by flux through the glycolytic, pentose phosphate, or the Entner-Doudoroff pathways. Variation of the metabolite constraints revealed central carbon metabolites, specifically upper glycolysis, tricarboxylic acid (TCA) cycle, and pentose phosphate, to be the most effective at training a predictive model, while energy and amino acid measurements were less effective. Irrespective of the measurement set, the metabolic fluxes (for the most part) remained unidentifiable. These findings suggested dynamic constraint-based modeling could aid in the design of cell-free protein expression experiments for metabolite prediction, but the flux estimation problem remains challenging. Furthermore, while we modeled the cell-free production of only a single protein in this study, the sequence specific dynamic constraint-based modeling approach presented here could be extended to multi-protein synthetic circuits, RNA circuits or even small molecule production. Full article
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Open AccessArticle Experimental Study on the Reinforcement Mechanism of Segmented Split Grouting in a Soft Filling Medium
Processes 2018, 6(8), 131; https://doi.org/10.3390/pr6080131
Received: 25 July 2018 / Revised: 10 August 2018 / Accepted: 13 August 2018 / Published: 17 August 2018
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Abstract
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
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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 mechanical properties and the impermeability of the soft filling medium before and after grouting was established. The results revealed that three different types of veins were formed as the distance from the grouting holes increased; namely, skeleton veins, cross-grid grouting veins, and parallel dispersed grouting veins. The thicknesses of the grouting veins decreased gradually, whereas the number of grouting veins increased. Moreover, the strikes of the grouting vein exhibited increased randomness. The reinforcement effect of segmental split grouting on soft filling media was mainly confirmed by the skeleton support and compaction. The elastic modulus of the grouting reinforcement solid increased on average by a factor that was greater than 100, and the permeability coefficient decreased on average by a factor that was greater than 40 in the direction of the parallel grouting vein with the most impermeable solid. The research results may be helpful in the investigation of the split grouting reinforcement mechanism under the condition of segmented grouting. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessConcept Paper Choosing the Optimal Multi-Point Iterative Method for the Colebrook Flow Friction Equation
Processes 2018, 6(8), 130; https://doi.org/10.3390/pr6080130
Received: 24 July 2018 / Revised: 10 August 2018 / Accepted: 14 August 2018 / Published: 16 August 2018
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Abstract
The Colebrook equation is implicitly given in respect to the unknown flow friction factor λ; λ=ζ(Re,ε*,λ) which cannot be expressed explicitly in exact way without simplifications and use of approximate calculus.
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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 representatives are Sharma–Guha–Gupta, Sharma–Sharma, Sharma–Arora, Džunić–Petković–Petković; Bi–Ren–Wu, Chun–Neta based on Kung–Traub, Neta, and the Jain method based on the Steffensen scheme. The recommended iterative methods can reach the final accurate solution with the least possible number of iterations. The approach is hybrid between the iterative procedure and one-step explicit approximations and can be used in engineering design for initial rough, but also for final fine calculations. Full article
(This article belongs to the Section Computational Methods)
Open AccessArticle Comparison of a Novel Miniaturized Screening Device with Büchi B290 Mini Spray-Dryer for the Development of Spray-Dried Solid Dispersions (SDSDs)
Processes 2018, 6(8), 129; https://doi.org/10.3390/pr6080129
Received: 2 July 2018 / Revised: 8 August 2018 / Accepted: 13 August 2018 / Published: 16 August 2018
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Abstract
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
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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 temperature (Tout)) and to provide particles with similar drug–polymer miscibility and morphology as laboratory-scale SDSDs. These findings confirm that the design and operation of this novel screening equipment mimic the microscale evaporation mechanism of a larger spray-dryer. The miniaturized spray-dryer was therefore able to provide a rational prediction of adequate polymer and drug loading (DL) for SDSD development while reducing active pharmaceutical ingredient (API) consumption by a factor of 120 and cycle time by a factor of 4. Full article
(This article belongs to the Section Materials Processes)
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Open AccessArticle Modelling Nutrients and Organics Removal by Biological Slow Filtration in Micro-Polluted Water Source Treatment
Processes 2018, 6(8), 128; https://doi.org/10.3390/pr6080128
Received: 17 July 2018 / Revised: 7 August 2018 / Accepted: 8 August 2018 / Published: 15 August 2018
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Abstract
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
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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 of nutrients and organics in the BSF system and obtained the optimal operating parameters as follows: filtration rate 0.1 m/h, filter depth 0.8 m, hydraulic head 0.64 m, temperature 26.06 °C. This study would provide a theoretical foundation for the actual application of biological slow filter in treatment of micro-polluted water in developing countries and offer an optimized basis for the design of operating conditions. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle A Strain-Based Percolation Model and Triaxial Tests to Investigate the Evolution of Permeability and Critical Dilatancy Behavior of Coal
Processes 2018, 6(8), 127; https://doi.org/10.3390/pr6080127
Received: 5 July 2018 / Revised: 4 August 2018 / Accepted: 6 August 2018 / Published: 13 August 2018
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Abstract
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
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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 volume-covering method proposed, the linear relationship between the fractal dimension and porosity indicates that the multiscale network can be a fractal percolation structure. A percolation model of connectivity by the axial strain-permeability relationship is proposed to explain the transition behavior of volumetric strain and CH4 seepage. The volumetric strain on permeability is illustrated by axial strain controlling the trend of transition behavior and radical strain controlling the shift of behavior. A good correlation between the theoretical and experimental results shows that the strain-based percolation model is effective in describing the transition behavior of CH4 seepage in coal. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessFeature PaperArticle A Cybernetic Approach to Modeling Lipid Metabolism in Mammalian Cells
Processes 2018, 6(8), 126; https://doi.org/10.3390/pr6080126
Received: 16 July 2018 / Revised: 3 August 2018 / Accepted: 7 August 2018 / Published: 12 August 2018
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Abstract
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
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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 population of near optimal parameter values, and a generalized constrained non-linear optimization employing a gradient search method was used to further refine the parameters. We validated our model by predicting an independent data set, the prostaglandin response of KLA primed ATP stimulated BMDM cells. We show that the cybernetic model captures the complex regulation of PG metabolism and provides a reliable description of PG formation. Full article
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Open AccessArticle Preparation and Characterization of Polyaluminum Titanium Silicate and its Performance in the Treatment of Low-Turbidity Water
Processes 2018, 6(8), 125; https://doi.org/10.3390/pr6080125
Received: 17 July 2018 / Revised: 7 August 2018 / Accepted: 8 August 2018 / Published: 11 August 2018
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Abstract
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
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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 produced by the reaction affected the PATC treatment of low-turbidity water. Scanning electron microscopy showed, that compared with polyaluminum chloride(PAC), the PATC cluster was more compact, showed greater pore structure, and presented better flocculation precipitation. The optimal reaction conditions were an initial turbidity of 10 nephelometric turbidity unit(NTU), PATC dosage of 9 mg/L, pH of 8 for the simulated water sample, stirring speed of 50 r/min, and settling time of 50 min, which were determined by Orthogonal experiment. The zeta potential of the reaction process was analyzed. In the treatment of low-turbidity water, PATC mainly functioned by adsorbing, bridging, and sweeping flocculation. Electrical neutralization played an auxiliary role. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessFeature PaperReview Computational Molecular Modeling of Transport Processes in Nanoporous Membranes
Processes 2018, 6(8), 124; https://doi.org/10.3390/pr6080124
Received: 19 July 2018 / Revised: 3 August 2018 / Accepted: 4 August 2018 / Published: 9 August 2018
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Abstract
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
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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 salt was purely a coulombic phenomenon. However, by applying molecular simulation techniques, it was clearly demonstrated that the solvation of ions made the separation in effect a steric separation and it was the flux which was strongly affected by the coulombic interactions between water and the membrane surface. Additionally, because of their relatively low cost and quick turnaround (by using multiple processor systems now increasingly available) simulations can be a useful screening tool to identify membranes for a potential application. To this end, we have described our studies in determining the most suitable zeolite membrane for redox flow battery applications. As computing facilities become more widely available and new computational methods are developed, we believe molecular modeling will become a key tool in the study of transport processes in nanoporous materials. Full article
(This article belongs to the Special Issue Transport of Fluids in Nanoporous Materials)
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Open AccessArticle Deformation and Hydraulic Conductivity of Compacted Clay under Waste Differential Settlement
Processes 2018, 6(8), 123; https://doi.org/10.3390/pr6080123
Received: 20 July 2018 / Revised: 5 August 2018 / Accepted: 6 August 2018 / Published: 8 August 2018
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Abstract
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.
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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 observed to begin cracking at settlement levels of 2.5 mm and 7 mm, respectively. When settlement reached 25 and 42.5 mm, cracks for 100 mm and 200 mm thick bentonite-sand mixtures without geogrid penetrated completely. The settlement levels for bentonite-sand mixtures of 100 mm thickness with and without geogrid reinforcement was found to be 10 mm and 15 mm, respectively, when its hydraulic conductivity was around 5 * 10−7 cm/s. In comparison, geogrid reinforced bentonite-sand mixtures was found to sustain large deformation with an enhanced imperviousness. The results from the present study can provide theory evidence of predicting deformation and hydraulic conductivity of the landfill cover system. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessReview Technology for the Remediation of Water Pollution: A Review on the Fabrication of Metal Organic Frameworks
Processes 2018, 6(8), 122; https://doi.org/10.3390/pr6080122
Received: 29 June 2018 / Revised: 22 July 2018 / Accepted: 3 August 2018 / Published: 8 August 2018
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Abstract
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
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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 materials such as active carbon. Their performance is often dependent on their structural distribution. To optimize the use of MOFs, their fabrication should be given more attention, without being limited to conventional preparation methods. Alternative preparation methods are given in this review, such as diffusion, solvent thermal, microwave, and ion thermal synthesis. Furthermore, developing functionalized MOFs is an available option to improve the removal efficiencies of a specific contaminant through pre-synthetic modification and post-synthesis modification. Post-synthesis modification has become a recent research hotspot. The coupling of MOFs with other techniques would be another option to ameliorate the remediation of water pollution. On one hand, their intrinsic drawbacks may be reduced. On the other hand, their performance may be enhanced due to their interaction behaviors. Overall, such coupling technologies are able to enhance the performance of an individual material. Because the excellent performance of MOF materials has been widely recognized and their developments have received wide attention, especially in environmental fields, in the present work we provide a review of fabrication of MOFs so as to motivate readers to deepen their understanding of the use of MOFs. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessArticle Effect of Particle Size on Carbon Nanotube Aggregates Behavior in Dilute Phase of a Fluidized Bed
Processes 2018, 6(8), 121; https://doi.org/10.3390/pr6080121
Received: 30 June 2018 / Revised: 31 July 2018 / Accepted: 6 August 2018 / Published: 8 August 2018
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Abstract
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
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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 solidity with gas velocity. A possible mechanism of aggregates formation was proposed based on the variations of aggregates properties with gas velocity. The obtained Heywood diameters of aggregates have been firstly correlated with the experimental parameter. Full article
(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes)
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Open AccessFeature PaperArticle A Coupled Thermal-Hydraulic-Mechanical Nonlinear Model for Fault Water Inrush
Processes 2018, 6(8), 120; https://doi.org/10.3390/pr6080120
Received: 1 July 2018 / Revised: 2 August 2018 / Accepted: 2 August 2018 / Published: 7 August 2018
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Abstract
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
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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 reflect the change of the seepage field in the fault and confined aquifer. This coupled THM model can provide a numerical simulation method to describe the coupled process of complex geological systems, which can be used to predict the fault water inrush induced by coal mining activities. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessFeature PaperArticle Effects of Pulse Interval and Dosing Flux on Cells Varying the Relative Velocity of Micro Droplets and Culture Solution
Processes 2018, 6(8), 119; https://doi.org/10.3390/pr6080119
Received: 28 June 2018 / Revised: 2 August 2018 / Accepted: 3 August 2018 / Published: 7 August 2018
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Abstract
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
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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 drug effect on cells could be analyzed more precisely especially for neuron cell dosing. Full article
(This article belongs to the Special Issue Transport of Fluids in Nanoporous Materials)
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Open AccessFeature PaperArticle Input Shaping Predictive Functional Control for Different Types of Challenging Dynamics Processes
Processes 2018, 6(8), 118; https://doi.org/10.3390/pr6080118
Received: 2 July 2018 / Revised: 18 July 2018 / Accepted: 23 July 2018 / Published: 7 August 2018
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Abstract
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,
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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. Full article
(This article belongs to the Special Issue Process Design, Integration, and Intensification)
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Open AccessCommunication A New Concept of Stirred Multiphase Reactor Using a Stationary Catalytic Foam
Processes 2018, 6(8), 117; https://doi.org/10.3390/pr6080117
Received: 28 June 2018 / Revised: 10 July 2018 / Accepted: 6 August 2018 / Published: 7 August 2018
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Abstract
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
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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. Full article
(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes)
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Open AccessFeature PaperReview Flotation in Water and Wastewater Treatment
Processes 2018, 6(8), 116; https://doi.org/10.3390/pr6080116
Received: 9 July 2018 / Revised: 26 July 2018 / Accepted: 1 August 2018 / Published: 7 August 2018
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Abstract
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
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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. Full article
(This article belongs to the Special Issue Wastewater Treatment Processes)
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Open AccessFeature PaperArticle Modeling the Dynamics of Human Liver Failure Post Liver Resection
Processes 2018, 6(8), 115; https://doi.org/10.3390/pr6080115
Received: 29 June 2018 / Revised: 30 July 2018 / Accepted: 1 August 2018 / Published: 4 August 2018
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Abstract
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
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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 liver fraction leading to longer time delay prior to failure. Our results suggest that, for a given remnant liver fraction, modulating a combination of cell death controlling parameters and metabolic load may help shift the clinical outcome away from post hepatectomy liver failure towards normal recovery. Full article
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Open AccessFeature PaperArticle Dynamic Optimization of a Subcritical Steam Power Plant Under Time-Varying Power Load
Processes 2018, 6(8), 114; https://doi.org/10.3390/pr6080114
Received: 2 June 2018 / Revised: 13 July 2018 / Accepted: 21 July 2018 / Published: 3 August 2018
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Abstract
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
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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-varying input trajectories that satisfy operability and safety constraints during the transition between plant states. An improvement in time-averaged efficiency of up to 1.8% points was shown to be feasible with corresponding savings in coal consumption of 184.8 tons/day and a carbon footprint decrease of 0.035 kg/kWh. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessArticle Numerical Simulation of Hydraulic Fracture Propagation in Coal Seams with Discontinuous Natural Fracture Networks
Processes 2018, 6(8), 113; https://doi.org/10.3390/pr6080113
Received: 29 June 2018 / Revised: 28 July 2018 / Accepted: 30 July 2018 / Published: 1 August 2018
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Abstract
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
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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, suggesting that the secondary fractures are an important part of the hydraulic fracture network in coal seams. In deep coal seams, the break pressure of discontinuous natural fractures mainly depends on the in-situ stress field and the direction of natural fractures. The mechanism of hydraulic fracture propagation in deep coal seams is significantly different from that in hard and tight rock layers. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessArticle 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)
Processes 2018, 6(8), 112; https://doi.org/10.3390/pr6080112
Received: 10 July 2018 / Revised: 20 July 2018 / Accepted: 29 July 2018 / Published: 1 August 2018
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Abstract
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
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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. Full article
(This article belongs to the Section Chemical Systems)
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Open AccessArticle A High-Order Numerical Manifold Method for Darcy Flow in Heterogeneous Porous Media
Processes 2018, 6(8), 111; https://doi.org/10.3390/pr6080111
Received: 19 June 2018 / Revised: 27 July 2018 / Accepted: 29 July 2018 / Published: 1 August 2018
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Abstract
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
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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 Darcy flow in heterogeneous porous media, while the refraction law is satisfied rigorously. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessArticle Experimental Study on the Creep Characteristics of Coal Measures Sandstone under Seepage Action
Processes 2018, 6(8), 110; https://doi.org/10.3390/pr6080110
Received: 28 June 2018 / Revised: 21 July 2018 / Accepted: 24 July 2018 / Published: 1 August 2018
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Abstract
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.
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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 deformation rate of sandstone increased rapidly with the increase of infiltration pressure. With the change of time, the change of permeability parameters went through three cycles; each cycle was divided into two stages, slow change stage and rapid change stage, and the rate of variation increased with the increase of the seepage pressure. Based on the macroscopic and microscopic characteristics of sandstone rupture, the connection between macroscopic and microscopic mechanism on sandstone rupture was established. The results in this paper can provide a theoretical basis for stability control of roadway surrounding rock in water-rich areas. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessCase Report Numerical Simulation on the Dynamic Characteristics of a Tremendous Debris Flow in Sichuan, China
Processes 2018, 6(8), 109; https://doi.org/10.3390/pr6080109
Received: 26 June 2018 / Revised: 23 July 2018 / Accepted: 24 July 2018 / Published: 1 August 2018
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Abstract
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
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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 and analyses. The flow field data obtained from numerical simulations were substituted into the finite element software ANSYS. Then the calculations of fluid-solid coupling action between the flow and dam had been done. All these results of simulations and analyses could be the guide and suggestion for the design and construction of prevention engineering of Zoumaling debris flow. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessArticle Fabrication of New Liquid Crystal Device Using Layer-by-Layer Thin Film Process
Processes 2018, 6(8), 108; https://doi.org/10.3390/pr6080108
Received: 29 June 2018 / Revised: 20 July 2018 / Accepted: 26 July 2018 / Published: 1 August 2018
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Abstract
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
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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 work demonstrated the good optoelectronic performance and alignment compatibility with LC molecules of the SWNT LBL assemblies, which are potential alternatives to ITO films as transparent electrodes for LCDs. Full article
(This article belongs to the Special Issue Thin Film Processes)
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Open AccessArticle Effect of Pore Fluid Pressure on the Normal Deformation of a Matched Granite Joint
Processes 2018, 6(8), 107; https://doi.org/10.3390/pr6080107
Received: 1 July 2018 / Revised: 20 July 2018 / Accepted: 24 July 2018 / Published: 1 August 2018
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Abstract
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
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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. Full article
(This article belongs to the Special Issue Fluid Flow in Fractured Porous Media)
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Open AccessFeature PaperArticle GEKKO Optimization Suite
Processes 2018, 6(8), 106; https://doi.org/10.3390/pr6080106
Received: 1 July 2018 / Revised: 19 July 2018 / Accepted: 23 July 2018 / Published: 31 July 2018
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Abstract
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
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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 examples of problems that are enabled by the GEKKO library. Full article
(This article belongs to the Special Issue Process Modelling and Simulation)
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Open AccessArticle Comparison between Two Solid-Liquid Extraction Methods for the Recovery of Steviol Glycosides from Dried Stevia Leaves Applying a Numerical Approach
Processes 2018, 6(8), 105; https://doi.org/10.3390/pr6080105
Received: 11 June 2018 / Revised: 24 July 2018 / Accepted: 26 July 2018 / Published: 30 July 2018
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Abstract
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
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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. Therefore, since diffusion and osmosis are highly dependent on temperature, it is necessary to control the temperature of the extraction system. On the other hand, the final aim of this work was to provide a scientific and quantitative basis for RSLDE. Therefore, the results obtained from stevia extracts using the corresponding mathematical model allowed hypothesizing the application of this model to the extraction processes of other vegetable matrices. Full article
(This article belongs to the Section Computational Methods)
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