Search results for: Porosity volume fraction

Authors: Wei-Neng Wang, Jhy-Yuan Shieh, Jhy-Hwa Chen, Juin-Jen Chang

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This paper incorporate tax evasion into a one-sector real business cycle (RBC) model to explores the quantitative interrelations between income tax rate and equilibrium (in)determinacy, and income tax rate is endogenously determined in order to balance the government budget. We find that the level of the effective income tax rate is key factor for equilibrium (in)determinacy, instead of the level of income tax rate in a tax evasion economy. Under an economy with tax evasion, the higher income tax rate is not sufficiently to lead to equilibrium indeterminate, it must combine with a necessary condition which is the lower fraction of tax evasion and that can result in agents' optimistic expectations to become self-fulfilling and sunspot fluctuation more likely to occur. On the other hand, an economy with tax evasion can see its macroeconomy become more stabilize, and a higher fraction of income tax evasion may has a stronger stabilizing effect.

Keywords: tax evasion, balanced-budget rule, equlibirium (in)determinacy, effective income tax rate

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Authors: Xin Li, Zhenxue Jiang, Zhuo Li

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Generally, shale gas is trapped within shale systems with low porosity and ultralow permeability as free and adsorbing states. Its production is controlled by properties, in terms of occurrence phases, gas contents, and percolation characteristics. These properties are all influenced by porous features. In this paper, porosity differences of marine shales were explored between Lower Cambrian shale and Lower Silurian shale of Sichuan Basin, South China. Both the two shales were marine shales with abundant oil-prone kerogen and rich siliceous minerals. Whereas Lower Cambrian shale (3.56% Ro) possessed a higher thermal degree than that of Lower Silurian shale (2.31% Ro). Samples were measured by a combination of organic-chemistry geology measurement, organic matter (OM) isolation, X-ray diffraction (XRD), N2 adsorption, and focused ion beam milling and scanning electron microscopy (FIB-SEM). Lower Cambrian shale presented relatively low pore properties, with averaging 0.008ml/g pore volume (PV), averaging 7.99m²/g pore surface area (PSA) and averaging 5.94nm average pore diameter (APD). Lower Silurian shale showed as relatively high pore properties, with averaging 0.015ml/g PV, averaging 10.53m²/g PSA and averaging 18.60nm APD. Additionally, fractal analysis indicated that the two shales presented discrepant pore morphologies, mainly caused by differences in the combination of pore types between the two shales. More specifically, OM-hosted pores with pin-hole shape and dissolved pores with dead-end openings were the main types in Lower Cambrian shale, while OM-hosted pore with a cellular structure was the main type in Lower Silurian shale. Moreover, porous characteristics of isolated OM suggested that OM of Lower Silurian shale was more capable than that of Lower Cambrian shale in the aspect of pore contribution. PV of isolated OM in Lower Silurian shale was almost 6.6 times higher than that in Lower Cambrian shale, and PSA of isolated OM in Lower Silurian shale was almost 4.3 times higher than that in Lower Cambrian shale. However, no apparent differences existed among samples with various matrix compositions. At late diagenetic or metamorphic epoch, extensive diagenesis overprints the effects of minerals on pore properties and OM plays the dominant role in pore developments. Hence, differences of porous features between the two marine shales highlight the effect of diagenetic degree on OM-hosted pore development. Consequently, distinctive pore characteristics may be caused by the different degrees of diagenetic evolution, even with similar matrix basics.

Keywords: marine shale, lower Cambrian, lower Silurian, om isolation, pore properties, om-hosted pore

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Authors: Tatyana A. Karpenyuk, Saltanat B. Orazova, Yana S. Tzurkan, Alla V. Goncharova, Bakytzhan K. Kairat, Togzhan D. Mukasheva, Ludmila V. Ignatova, Ramza Z. Berzhanova

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Microalgae due to the ability to accumulate high levels of practically valuable polyunsaturated fatty acids attract attention as a promising raw material for commercial products. It were defined the features of the growth processes of cells green protococcal microalgae Oocystis rhomboideus, Scenedesmus obliquus, Dictyochlorella globosa at cultivation in different nutritional mediums. For the rapid accumulation of biomass, combined with high productivity of total lipids fraction yield recommended to use the Fitzgerald medium (Scenodesmus obliquus, Oocystis rhomboideus) and/or Bold medium (Dictyochlorella globosa). Productivity of lipids decreased in sequence Dictyochlorella globosa > Scenodesmus obliquus > Oocystis rhomboideus. The bulk of fatty acids fraction of the total lipids is unsaturated fatty acids, which accounts for 70 to 83% of the total number of fatty acids. The share of monoenic acids varies from 16 to 36 %, the share of unsaturated fatty acids - from 44 to 65% of total fatty acids fraction. Among the unsaturated acids dominate α-linolenic acid (C18:3n-3), hexadecatetraenic acid (C16:4) and linoleic acid (C18:2).

Keywords: microalgae, lipids, fatty acids, culture conditions

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Authors: C. Malça, P. Gonçalves, N. Alves, A. Mateus

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Regardless of the manufacturing process used, subtractive or additive, material, purpose and application, produced components are conventionally solid mass with more or less complex shape depending on the production technology selected. Aspects such as reducing the weight of components, associated with the low volume of material required and the almost non-existent material waste, speed and flexibility of production and, primarily, a high mechanical strength combined with high structural performance, are competitive advantages in any industrial sector, from automotive, molds, aviation, aerospace, construction, pharmaceuticals, medicine and more recently in human tissue engineering. Such features, properties and functionalities are attained in metal components produced using the additive technique of Rapid Prototyping from metal powders commonly known as Selective Laser Melting (SLM), with optimized internal topologies and varying densities. In order to produce components with high strength and high structural and functional performance, regardless of the type of application, three different internal topologies were developed and analyzed using numerical computational tools. The developed topologies were numerically submitted to mechanical compression and four point bending testing. Finite Element Analysis results demonstrate how different internal topologies can contribute to improve mechanical properties, even with a high degree of porosity relatively to fully dense components. Results are very promising not only from the point of view of mechanical resistance, but especially through the achievement of considerable variation in density without loss of structural and functional high performance.

Keywords: additive manufacturing, internal topologies, porosity, rapid prototyping, selective laser melting

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Authors: G. Massaad, E. Roziere, A. Loukili, L. Izoret

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Based on the monitoring of mass, hydrostatic weighing, and the amount of leached OH- we deduced the nature of leached and precipitated minerals, the amount of lost aggregates and the evolution of porosity and cracking during the sulphate attack. Using these information, we are able to draw the volume / mass changes brought by mineralogical variations and cracking of the cement matrix. Then we defined a new performance indicator, the averaged density, capable to resume along the test of sulphate attack the occurred physicochemical variation occurred in the cementitious matrix and then highlight.

Keywords: monitoring strategy, performance indicator, sulphate attack, mechanism of degradation

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Authors: Mohammad Alroaithi

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Porous polymeric materials have attracted a great attention due to their distinctive porous structure within a polymer matrix. They are characterised by the presence of external pores on the surface as well as inner interconnected windows. Conventional techniques to produce porous polymeric materials encounters major challenge in controlling the properties of the resultant structures including morphology, pores, cavities size, and porosity. Herein, we present a facile and versatile microfluidics technique for the fabrication of uniform porous polymeric structures with highly ordered and well-defined interconnected windows. The shapes of the porous structures can either be a microparticles or foam. Both shapes used microfluidics platform to first produce monodisperse emulsion. The uniform emulsions, were then consolidated into porous structures through UV photopolymerisation. The morphology, pores, cavities size, and porosity of the structures can be precisely manipulated by the flowrate. The proposed strategy might provide a key advantage for fabrication of uniform porous materials over many existing technologies.

Keywords: polymer, porous particles, microfluidics, porous structures

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Authors: Aptullah Karakas, Murat Baydogan

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Hot-dip aluminizing (HDA) is one of the several aluminizing methods to form a wear-, corrosion- and oxidation-resistant aluminide layers on the surface. In this method, the substrate is dipped into a molten aluminum bath, hold in the bath for several minutes, and cooled down to the room temperature in air. A subsequent annealing after the HDA process is generally performed. The main advantage of HDA is its very low investment cost in comparison with other aluminizing methods such as chemical vapor deposition (CVD), pack aluminizing and metalizing. In the HDA process, Al or Al-Si molten baths are mostly used. However, in this study, three different Al alloys such as Al4043 (Al-Mg), Al5356 (Al-Si) and Al7020 (Al-Zn) were used as the molten bath in order to see their effects on morphological and mechanical properties of the resulting aluminide layers. AISI 4140 low alloyed steel was used as the substrate. Parameters of the HDA process were bath composition, bath temperature, and dipping time. These parameters were considered within a Taguchi L9 orthogonal array. After the HDA process and subsequent diffusion annealing, coating thickness measurement, microstructural analysis and hardness measurement of the aluminide layers were conducted. The optimum process parameters were evaluated according to coating morphology, such as cracks, Kirkendall porosity and hardness of the coatings. According to the results, smooth and clean aluminide layer with less Kirkendall porosity and cracks were observed on the sample, which was aluminized in the molten Al7020 bath at 700 C for 10 minutes and subsequently diffusion annealed at 750 C. Hardness of the aluminide layer was in between 1100-1300 HV and the coating thickness was approximately 400 µm. The results were promising such that a hard and thick aluminide layer with less Kirkendall porosity and cracks could be formed. It is, therefore, concluded that Al7020 bath may be used in the HDA process of AISI 4140 steel substrate.

Keywords: hot-dip aluminizing, microstructure, hardness measurement, diffusion annealing

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Authors: Imane Benghalia, Mohammed Zamoum, Rachid Boucetta

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Hydrodynamic cavitation is a complex physical phenomenon that appears in hydraulic systems (pumps, turbines, valves, Venturi tubes, etc.) when the fluid pressure decreases below the saturated vapor pressure. The works carried out in this study aimed to get a better understanding of the cavitating flow phenomena. For this, we have numerically studied a cavitating bubbly flow through a Venturi nozzle. The cavitation model is selected and solved using a commercial computational fluid dynamics (CFD) code. The obtained results show the effect of the inlet pressure (10, 7, 5, and 2 bars) of the Venturi on pressure, the velocity of the fluid flow, and the vapor fraction. We found that the inlet pressure of the Venturi strongly affects the evolution of the pressure, velocity, and vapor fraction formation in the cavitating flow.

Keywords: cavitating flow, CFD, phase change, venturi

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Authors: R. Vidhya, M. Navamuniyammal M. Sivakumar, S. Reeta

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The unplanned urbanization affects the environment due to pollution, conditions of the atmosphere, decreased vegetation and the pervious and impervious soil surface. Considered to be a cumulative effect of all these impacts is the Urban Heat Island. In this paper, the urban heat island effect is studied for the Chennai city, TamilNadu, South India using satellite remote sensing data. LANDSAT 8 OLI and TIRS DATA acquired on 9th September 2014 were used to Land Surface Temperature (LST) map, vegetation fraction map, Impervious surface fraction, Normalized Difference Water Index (NDWI), Normalized Difference Building Index (NDBI) and Normalized Difference Vegetation Index (NDVI) map. The relationship among LST, Vegetation fraction, NDBI, NDWI, and NDVI was calculated. The Chennai city’s Urban Heat Island effect is significant, and the results indicate LST has strong negative correlation with the vegetation present and positive correlation with NDBI. The vegetation is the main factor to control urban heat island effect issues in urban area like Chennai City. This study will help in developing measures to land use planning to reduce the heat effects in urban area based on remote sensing derivatives.

Keywords: land surface temperature, brightness temperature, emissivity, vegetation index

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Authors: Twin Aji Kusumagiani, Eleonora Agustine, Dini Fitriani

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The value changes of soil physical properties in the agricultural area are giving impacts on soil fertility. This can be caused by excessive usage of inorganic fertilizers and imbalances on organic fertilization. Soil physical parameters that can be measured include soil electrical conductivity, water content volume, soil porosity, dielectric permittivity, etc. This study used the electrical conductivity and volume water content as the measured physical parameters. The study was conducted on volcanic soil obtained from agricultural land conditioned with NPK fertilizer and salt in a certain amount. The dimension of the conditioned soil being used is 1 x 1 x 0.5 meters. By using this method, we can delineate the soil electrical conductivity value of land due to changes in the provision of inorganic NPK fertilizer and the salinity in the soil. Zone with the additional 1 kg of salt has the dimension of 60 cm in width, 20 cm in depth and 1 cm in thickness while zone with the additional of 10 kg NPK fertilizer has the dimensions of 70 cm in width, 20 cm in depth and 3 cm in thickness. This salt addition resulted in EC values changes from the original condition. Changes of the EC value tend to occur at a depth of 20 to 40 cm on the line 1B at 9:45 dS/cm and line 1C of 9.35 dS/cm and tend to have the direction to the Northeast.

Keywords: EC, electrical conductivity, VWC, volume water content, NPK fertilizer, salt, volcanic soil

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Authors: Mahdi Aghaei, Saeid Jamshidi, Mastaneh Hajipour

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Effective factors on the mechanical wellbore stability are divided in to two categories: 1) Controllable factors, 2) Uncontrollable factors. The purpose of geo-mechanical modeling of wells is to determine the limit of controlled parameters change based on the stress regime at each point and by solving the governing equations the pore-elastic environment around the well. In this research, the mechanical analysis of wellbore stability was carried out for Soroush oilfield. For this purpose, the geo-mechanical model of the field is made using available data. This model provides the necessary parameters for obtaining the distribution of stress around the wellbore. Initially, a basic model was designed to perform various analysis, based on obtained data, using Abaqus software. All of the subsequent sensitivity analysis such as sensitivity analysis on porosity, permeability, etc. was done on the same basic model. The results obtained from these analysis gives various result such as: with the constant geomechanical parameters, and sensitivity analysis on porosity permeability is ineffective. After the most important parameters affecting the wellbore stability and instability are geo-mechanical parameters.

Keywords: wellbore stability, movement, stress, instability

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Authors: Hande Barkan-Ozturk, Angelika Menner, Alexander Bismarck

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Microfluidic mixing technology grew rapidly in the past few years due to its many advantages over the macro-scale mixing, especially the ability to use small amounts of internal volume and also very high surface-to-volume ratio. The Reynold number identify whether the mixing is operated by the laminar or turbulence flow. Therefore, mixing with very fast kinetic can be achieved by diminishing the channel dimensions to decrease Reynold number and the laminar flow can be accomplished. Moreover, by using obstacles in the micromixer, the mixing length and the contact area between the species have been increased. Therefore, the channel geometry and its surface property have great importance to reach satisfactory mixing results. Since poly(-merised) High Internal Phase Emulsions (polyHIPEs) have more than 74% porosity and their pores are connected each other with pore throats, which cause high permeability, they are ideal candidate to build a micromixer. The HIPE precursor is commonly produced by using an overhead stirrer to obtain relatively large amount of emulsion in batch process. However, we will demonstrate that a desired amount of emulsion can be prepared continuously with micromixer build from polyHIPE, and such HIPE can subsequently be employed as ink in 3D printing process. In order to produce the micromixer a poly-Pickering(St-co-DVB)HIPE with 80% porosity was prepared with modified silica particles as stabilizer and surfactant Hypermer 2296 to obtain open porous structure and after coating of the surface, the three 1/16' ' PTFE tubes to transfer continuous (CP) and internal phases (IP) and the other is to collect the emulsion were placed. Afterwards, the two phases were injected in the ratio 1:3 CP:IP with syringe dispensers, respectively, and highly viscoelastic H(M)IPE, which can be used as an ink in 3D printing process, was gathered continuously. After the polymerisation of the resultant emulsion, polyH(M)IPE has interconnected porous structure identical to the monolithic polyH(M)IPE indicating that the emulsion can be prepared constantly with poly-Pickering-HIPE as micromixer and it can be used to prepare desired pattern with a 3D printer. Moreover, the morphological properties of the emulsion can be adjustable by changing flow ratio, flow speed and structure of the micromixer.

Keywords: 3D-Printing, emulsification, macroporous polymer, micromixer, polyHIPE

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Authors: Kyoung Hoon Kim

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A thermodynamic analysis of a partial evaporating Rankine cycle with regeneration using zeotropic ammonia-water mixture as a working fluid is presented in this paper. The thermodynamic laws were applied to evaluate the system performance. Based on the thermodynamic model, the effects of the vapor quality and the ammonia mass fraction on the system performance were extensively investigated. The results showed that thermal efficiency has a peak value with respect to the vapor quality as well as the ammonia mass fraction. The partial evaporating ammonia based Rankine cycle has a potential to improve recovery of low-grade finite heat source.

Keywords: ammonia-water, Rankine cycle, partial evaporating, thermodynamic performance

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Authors: Michael Russelle S. Alvarez, Noel S. Quiming, Francisco M. Heralde

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This study aims to: a) obtain ethanolic (95% EtOH) and aqueous extracts of Selaginella elmeri, Christella dentata, Elatostema sinnatum, Curculigo capitulata, Euphorbia hirta, Murraya koenigii, Alpinia speciosa, Cymbopogon citratus, Eucalyptus globulus, Jatropha curcas, Psidium guajava, Gliricidia sepium, Ixora coccinea and Capsicum frutescens and screen them for larvicidal activities against Aedes aegypti (Linn.) and Aedes albopictus (Skuse) larvae; b) to fractionate the most active extract and determine the most active fraction; c) to determine the larvicidal properties of the most active extract and fraction against by computing their percentage mortality, LC50, and LC90 after 24 and 48 hours of exposure; and d) to determine the nature of the components of the active extracts and fractions using phytochemical screening. Ethanolic (95% EtOH) and aqueous extracts of the selected plants will be screened for potential larvicidal activity against Ae. aegypti and Ae. albopictus using standard procedures and 1% malathion and a Piper nigrum based ovicide-larvicide by the Department of Science and Technology as positive controls. The results were analyzed using One-Way ANOVA with Tukey’s and Dunnett’s test. The most active extract will be subjected to partial fractionation using normal-phase column chromatography, and the fractions subsequently screened to determine the most active fraction. The most active extract and fraction were subjected to dose-response assay and probit analysis to determine the LC50 and LC90 after 24 and 48 hours of exposure. The active extracts and fractions will be screened for phytochemical content. The ethanolic extracts of C. citratus, E. hirta, I. coccinea, G. sepium, M. koenigii, E globulus, J. curcas and C. frutescens exhibited significant larvicidal activity, with C. frutescens being the most active. After fractionation, the ethyl acetate fraction was found to be the most active. Phytochemical screening of the extracts revealed the presence of alkaloids, tannins, indoles and steroids. A formulation using talcum powder–300 mg fraction per 1 g talcum powder–was made and again tested for larvicidal activity. At 2 g/L, the formulation proved effective in killing all of the test larvae after 24 hours.

Keywords: larvicidal activity screening, partial purification, dose-response assay, capsicum frutescens

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Authors: Hela Ayeb Mrabtini, Ghazi Bellakhal, Jamel Chahed

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The presence of the dispersed phase in gas-liquid bubbly flow considerably alters the liquid turbulence. The bubbles induce turbulent fluctuations that enhance the global liquid turbulence level and alter the mechanisms of turbulence. RANS modeling of uniformly sheared flows on an isolated sphere centered in a control volume is performed using first and second order turbulence closures. The sphere is placed in the production-dissipation equilibrium zone where the liquid velocity is set equal to the relative velocity of the bubbles. The void fraction is determined by the ratio between the sphere volume and the control volume. The analysis of the turbulence statistics on the control volume provides numerical results that are interpreted with regard to the effect of the bubbles wakes on the turbulence structure in uniformly sheared bubbly flow. We assumed for this purpose that at low void fraction where there is no hydrodynamic interaction between the bubbles, the single-phase flow simulation on an isolated sphere is representative on statistical average of a sphere network. The numerical simulations were firstly validated against the experimental data of bubbly homogeneous turbulence with constant shear and then extended to produce numerical results for a wide range of shear rates from 0 to 10 s^-1. These results are compared with our turbulence closure proposed for gas-liquid bubbly flows. In this closure, the turbulent stress tensor in the liquid is split into a turbulent dissipative part produced by the gradient of the mean velocity which also contains the turbulence generated in the bubble wakes and a pseudo-turbulent non-dissipative part induced by the bubbles displacements. Each part is determined by a specific transport equation. The simulations of uniformly sheared flows on an isolated sphere reproduce the mechanisms related to the turbulent part, and the numerical results are in perfect accordance with the modeling of the transport equation of the turbulent part. The reduction of second order turbulence closure provides a description of the modification of turbulence structure by the bubbles presence using a dimensionless number expressed in terms of two-time scales characterizing the turbulence induced by the shear and that induced by bubbles displacements. The numerical simulations carried out in the framework of a comprehensive analysis reproduce particularly the attenuation of the turbulent friction showed in the experimental results of bubbly homogeneous turbulence subjected to a constant shear.

Keywords: gas-liquid bubbly flows, homogeneous turbulence, turbulence closure, uniform shear

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Authors: María del Carmen Recio-Ruiz, Ramiro Ruiz-Rosas, Juana María Rosas, José Rodríguez-Mirasol, Tomás Cordero

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At the present time, conventional fossil fuels show environmental and sustainability disadvantages with regard to renewables energies. Producing energy and chemicals from biomass is an interesting alternative for substitution of conventional fossil sources with a renewable feedstock while enabling zero net greenhouse gases emissions. Pyrolysis is a well-known process to produce fuels and chemicals from biomass. In this work, conventional and fast pyrolysis of different agro-industrial residues (almond shells, hemp hurds, olive stones, and Kraft lignin) was studied. Both processes were carried out in a fixed bed reactor under nitrogen flow and using different operating conditions to analyze the influence of temperature (400-800 ºC) and heating rate (10 and 20 ºC/minfor conventional pyrolysis and 50 ºC/s for fast pyrolysis)on the yields, products distribution, and composition of the different fractions. The results showed that for both conventional and fast pyrolysis, the solid fraction yield decreased with temperature, while the liquid and gas fractions increased. In the case of the fast pyrolysis, a higher content of liquid fraction than that obtained in conventional pyrolysis could be observed due to cracking reactions occur at a lesser extent. With respect to the composition of de non-condensable fraction, the main gases obtained were CO, CO₂ (mainly at low temperatures), CH₄, and H₂ (mainly at high temperatures).

Keywords: bio-oil, biomass, conventional pyrolysis, fast pyrolysis

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Authors: Tahira Pirzada, Zahra Ashrafi, Saad Khan

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We present a facile and sustainable solid templating approach to fabricate highly porous, flexible and superhydrophobic aerogels of composite nanofibers of cellulose diacetate and silica which are produced through sol gel electrospinning. Scanning electron microscopy, contact angle measurement, and attenuated total reflection-Fourier transform infrared spectrometry are used to understand the structural features of the resultant aerogels while thermogravimetric analysis and differential scanning calorimetry demonstrate their thermal stability. These aerogels exhibit a self-supportive three-dimensional network abundant in large secondary pores surrounded by primary pores resulting in a highly porous structure. Thermal crosslinking of the aerogels has further stabilized their structure and flexibility without compromising on the porosity. Ease of processing, thermal stability, high porosity and oleophilic nature of these aerogels make them promising candidate for a wide variety of applications including acoustic and thermal insulation and oil and water separation.

Keywords: hybrid aerogels, sol-gel electrospinning, oil-water separation, nanofibers

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Authors: Özlem Arpacı, Zeliha Soysal, Nuran Diril

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Benzoxazoles are heterocyclic compounds that have a fused benzene and an oxazole ring. These heterocyclic compounds are reported to have antibacterial, antitubercular, antifungal, antiviral, antioxidant and anticancer activities. In this study, some benzoxazole derivatives that have broad antimicrobial and potent antitumoral activities, are investigated their mutagenic activities with using the Ames Test. The Ames test was conducted using Salmonella typhimurium TA98, TA100 and TA102 tester strains in the standard plate incorporation assay in the absence of liver S9 fraction. The results are evaluated using SPSS and none of the benzoxazole derivatives showed mutagenic activity using the Ames test in the absence of S9 liver fraction.

Keywords: benzoxazoles, ames test, mutagenic activity, antimutagenic activity, antitumoral activity

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Authors: Amit Kumar Bhandary, Prithviraj Gupta, Siddhartha Mukherjee, Mahua Ghosh Chaudhuri, Rajib Dey

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Chromite ores are primarily used for extraction of chromium, which is an expensive metal. For low grade chromite ores (containing less than 40% Cr₂O₃), the chromium extraction is not usually economically viable. India possesses huge quantities of low grade chromite reserves. This deposit can be utilized after proper physical beneficiation. Magnetic separation techniques may be useful after reduction for the beneficiation of low grade chromite ore. The sample collected from the sukinda mines is characterized by XRD which shows predominant phases like maghemite, chromite, silica, magnesia and alumina. The raw ore is crushed and ground to below 75 micrometer size. The microstructure of the ore shows that the chromite grains surrounded by a silicate matrix and porosity observed the exposed side of the chromite ore. However, this ore may be utilized in refractory applications. Chromite ores contain Cr₂O₃, FeO, Al₂O₃ and other oxides like Fe-Cr, Mg-Cr have a high tendency to form spinel compounds, which usually show high refractoriness. Initially, the low grade chromite ore (containing 34.8% Cr₂O₃) was reduced at 1200 ⁰C for 80 minutes with 30% coke fines by weight, before being subjected to magnetic separation. The reduction by coke leads to conversion of higher state of iron oxides converted to lower state of iron oxides. The pre-reduced samples are then characterized by XRD. The magnetically inert mass was then reacted with 20% MgO by weight at 1450 ⁰C for 2 hours. The resultant product was then tested for various refractoriness parameters like apparent porosity, slag resistance etc. The results were satisfactory, indicating that the resultant spinel compounds are suitable for refractory applications for elevated temperature processes.

Keywords: apparent porosity, beneficiation, low-grade chromite, refractory, spinel compounds, slag resistance

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Authors: Stella O. Olubodun, George E. Eriyamremu

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The study examined the effect of Bonny Light whole crude oil (WC) and its water soluble fraction (WSF) on the activities of antioxidant enzymes (catalase (CAT) and superoxide dismutase (SOD)) and crude mitochondria ATPases in the radicle of germinating bean (Vigna unguiculata). The percentage germination, level of lipid peroxidation, antioxidant enzyme, and mitochondria Ca2+ and Mg2+ ATPase activities were measured in the radicle of bean after 7, 14, and 21 days post germination. Viable bean seeds were planted in soils contaminated with 10ml, 25ml, and 50ml of whole crude oil (WC) and its water soluble fraction (WSF) to obtain 2, 5, and 10% v/w crude oil contamination. There was dose dependent reduction of the number of bean seeds that germinated in the contaminated soils compared with control (p<0.001). The activities of the antioxidant enzymes, as well as, adenosine triphosphatase enzymes, were also significantly (p<0.001) altered in the radicle of the plants grown in contaminated soil compared with the control. Generally, the level of lipid peroxidation was highest after 21 days post germination when compared with control. Stress to germinating bean caused by Bonny Light crude oil or its water soluble fraction resulted in adaptive changes in crude mitochondria ATPases in the radicle.

Keywords: antioxidant enzymes, bonny light crude oil, radicle, mitochondria ATPases

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Authors: Abdalrahman D. Alsulaili, Sheikha Y. Aljeraiwi, Athba N. Almanaie, Raghad Y. Alhajeri, Mariam Z. Almijren

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The water accompanying oil in the oil production process is increasing and due to its increasing rates a problem with handling it occurred. Current solutions like discharging into the environment, dumping water in evaporation pits, usage in the industry and reinjection in oil reservoirs to enhance oil production are used worldwide. The water injection method has been introduced to the oil industry with a process that either immediately injects water to the reservoir or goes to the filtration process before injection all depending on the porosity of the soil. Reinjection of unfiltered effluent water with high Total Suspended Solid (TSS) and Oil in Water (O/W) into soils with low porosity cause a blockage of pores, whereas soils with high porosity do not need high water quality. Our study mainly talks about the filtration and adsorption of the water using organic media as the adsorbent. An adsorbent is a substance that has the ability to physically hold another substance in its surface. Studies were done on nutshell and date pits with different surface areas and flow rates by using a 10inch filter connected with three tanks to perform as one system for the filtration process. Our approach in the filtration process using different types of medias went as follow: starting first with crushed nutshell, second with ground nutshell, and third using carbonized date pits with medium flow rate then high flow rate to compare different results. The result came out nearly as expected from our study where both O/W and TSS were reduced from our oily water sample by using this organic material. The effect of specific area was noticed when using nutshell as the filter media, where the crushed nutshell gave us better results than ground nutshell. The effect of flow rate was noticed when using carbonized date pits as the filter media whereas the treated water became more acceptable when the flow rate was on the medium level.

Keywords: date pits, nutshell, oil water, TSS

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Authors: Basem A. El Werfallia, Osama R. Shaltamiab, Ragab M. Al Alwanyc

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The present work aims to characterize the geochemistry of the beach sands along the Mediterranean Coast from Al Kuwifia to Tolmeita, NE Libya. The major oxides CaO and MgO are the main constituents of the carbonate minerals; calcite and aragonite. SiO2 is mainly in the form of quartz. Sometimes a high quotient of SiO2 together with the oxides; Al2O3, K2O and partly of Na2O, TiO2 and Fe2O3 are essentially allocated within the structure of the feldspars. Part of Na2O and the content of Cl belong mainly to halite. Part of Fe2O3 and TiO2 may be accommodated as iron oxyhydroxides. Part of CaO and the content of SO3 are allotted within the gypsum structure. Ba, Sr, Th, U and REE are basicallycontrolled by the carbonate fraction, while Cu, Zn, V and Cr are strongly correlated with Al2O3.

Keywords: geochemistry, major oxides, Al Kuwifia, Tolmeita

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Authors: J. Shiri, A. Mansourizadeh, F. Faghih, H. Vaez

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In this study, porous polyvinylidene fluoride (PVDF) hollow fiber membranes are fabricated via a wet phase-inversion Process and used in the gas–liquid membrane contactor for physical CO2 absorption. Effect of different air gap on the structure and CO2 flux of the membrane was investigated. The hollow fibers were prepared using the wet spinning process using a dope solution containing PVDF/NMP/Licl (18%, 78%, 4%) at the extrusion rate of 4.5ml/min and air gaps of 0, 7, 15cm. Water was used as internal and external coagulants. Membranes were characterized using various techniques such as Field Emission Scanning Electron Microscopy (FESEM), Gas permeation test, Critical Water Entry Pressure (CEPw) to select the best membrane structure for Co2 absorption. The characterization results showed that the prepared membrane at which air gap possess small pore size with high surface porosity and wetting resistance, which are favorable for gas absorption application air gap increased, CEPw had a decrease, but the N2 permeation was decreased. Surface porosity and also Co2 absorption was increased.

Keywords: porous PVDF hollow fiber membrane, CO2 absorption, phase inversion, air gap

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Authors: Basem A. El Werfalli, Osama R. Shaltamiab, Ragab M. Al Alwany

Abstract:

The present work aims to characterize the geochemistry of the beach sands along the Mediterranean Coast from Al Kuwifia to Tolmeita, NE Libya. The major oxides CaO and MgO are the main constituents of the carbonate minerals; calcite and aragonite. SiO₂ is mainly in the form of quartz. Sometimes a high quotient of SiO₂ together with the oxides; Al₂O₃, K₂O and partly of Na₂O, TiO₂ and Fe₂O₃ are essentially allocated within the structure of the feldspars. Part of Na₂O and the content of Cl belong mainly to halite. Part of Fe₂O₃ and TiO₂ may be accommodated as iron oxyhydroxides. Part of CaO and the content of SO₃ are allotted within the gypsum structure. Ba, Sr, Th, U and REE are basically controlled by the carbonate fraction, while Cu, Zn, V and Cr are strongly correlated with Al₂O₃.

Keywords: geochemistry, major oxides, Al Kuwifia, Tolmeita

Procedia PDF Downloads 117

Authors: Peter Križan, Juraj Beniak, Ľubomír Šooš, Miloš Matúš

Abstract:

Biomass treatment through densification is very suitable and important technology before its effective energy recovery. Densification process of biomass is significantly influenced by various technological and also material parameters which are ultimately reflected on the final solid Biofuels quality. The paper deals with the experimental research of the relationship between technological and material parameters during densification of fast-growing trees, roundly fast-rowing willow. The main goal of presented experimental research is to determine the relationship between pressing pressure raw material fraction size from a final briquettes density point of view. Experimental research was realized by single-axis densification. The impact of fraction size with interaction of pressing pressure and stabilization time on the quality properties of briquettes was determined. These parameters interaction affects the final solid biofuels (briquettes) quality. From briquettes production point of view and also from densification machines constructions point of view is very important to know about mutual interaction of these parameters on final briquettes quality. The experimental findings presented here are showing the importance of mentioned parameters during the densification process.

Keywords: briquettes density, densification, fraction size, pressing pressure, stabilization time

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Authors: H. Bayat, M. Majidi, M. Bolhasani, A. Karbalaie Alilou, A. Mirabdolah Lavasani

Abstract:

Unsteady flow and heat transfer from a circular cylinder in cross-flow is studied numerically. The governing equations are solved by using finite volume method. Reynolds number varies in range of 50 to 200, in this range flow is considered to be laminar and unsteady. Al2O3 nanoparticle with volume fraction in range of 5% to 20% is added to pure water. Effects of adding nanoparticle to pure water on lift and drag coefficient and Nusselt number is presented. Addition of Al2O3 has inconsiderable effect on the value of drags and lift coefficient. However, it has significant effect on heat transfer; results show that heat transfer of Al2O3 nanofluid is about 9% to 36% higher than pure water.

Keywords: nanofluid, heat transfer, unsteady flow, forced convection, cross-flow

Procedia PDF Downloads 372

Authors: Abrar Al-Mutairi, Talal Al-Bazali

Abstract:

In this study, changes in capillary entry pressure of shale, as it interacts with CO₂, under different temperatures (25 °C to 250 °C) have been investigated. The combined impact of temperature and petrophysical properties (water content, water activity, permeability and porosity) of shale was also addressed. Results showed that the capillary entry pressure of shale when it interacted with CO₂ was highly affected by temperature. In general, increasing the temperature decreased capillary entry pressure of shale. We believe that pore dilation, where pore throat size expands due to the application of heat, may have caused this decrease in capillary entry pressure of shale. However, in some cases we found that at higher temperature some shale samples showed that the temperature activated clay swelling may have caused an apparent decrease in pore throat radii of shale which translates into higher capillary entry pressure of shale. Also, our results showed that there is no distinct relationship between shale’s water content, water activity, permeability, and porosity on the capillary entry pressure of shale samples as it interacted with CO₂ at different temperatures.

Keywords: heat, threshold pressure, CO₂ sequestration, shale

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Authors: Abdul Manan

Abstract:

Dielectric Resonators (DRs) have revolutionized the microwave wireless communication industry globally. There are three directions for research in ceramics for application in telecommunication industry Three key properties of ceramic dielectrics that determine their functionality at microwave and millimetrewave frequencies include relative permittivity (εr), unloaded quality factor Qu- the inverse of the dielectric loss (tanδ) and temperature coefficient of resonant frequency (τf). Each direction requires specific properties. These dielectric properties are affected by a number of factors. These includes tolerance factor, onset of structural phase transitions, dark core formation, processing conditions, raw materials and impurities, order/disorder behavior, compositional ordering, porosity, humidity, grain size, orientation of the crystallites, and grain boundaries. The data related to these factors is scattered. The main purpose of this review is to bring these together and present the effects of these factors on the microwave dielectric properties. Control of these factors is important for improvement in the microwave properties. This review would be very helpful to the novice researchers and technologists in the field.

Keywords: order disorder, sintering, defect, porosity, grain boundaries

Procedia PDF Downloads 367

Authors: L. Chevez, A. Apaza, J. Rodriguez, R. Puga, H. Loro, Juan Z. Davalos

Abstract:

Virtual Dimension (VD) procedure is used to analyze Hyperspectral Image (HIS) treatment-data in order to estimate the abundance of mineral components of a mining sample. Hyperspectral images coming from reflectance spectra (NIR region) are pre-treated using Standard Normal Variance (SNV) and Minimum Noise Fraction (MNF) methodologies. The endmember components are identified by the Simplex Growing Algorithm (SVG) and after adjusted to the reflectance spectra of reference-databases using Simulated Annealing (SA) methodology. The obtained abundance of minerals of the sample studied is very near to the ones obtained using XRD with a total relative error of 2%.

Keywords: hyperspectral imaging, minimum noise fraction, MNF, simplex growing algorithm, SGA, standard normal variance, SNV, virtual dimension, XRD

Procedia PDF Downloads 134

Authors: Chaitanya R. Mali, V. Vinod, Ashwin W. Patwardhan

Abstract:

Design of long vertical steam generator (SG) tubes in nuclear power plant involves an understanding of different aspects of flow boiling phenomenon such as flow instabilities, flow regimes, dry out, critical heat flux, pressure drop, etc. The knowledge of the prediction of local thermal hydraulic characteristics is necessary to understand these aspects. For this purpose, the methodology has been developed which covers all the flow boiling regimes to model full range flow boiling phenomenon. In this methodology, the vertical tube is divided into four sections based on vapor fraction value at the end of each section. Different modeling strategies have been applied to the different sections of the vertical tube. Computational fluid dynamics simulations have been performed on a vertical SG tube of 0.0126 m inner diameter and 23 m length. The thermal hydraulic parameters such as vapor fraction, liquid temperature, heat transfer coefficient, pressure drop, heat flux distribution have been analyzed for different designed heat duties (1.1 MW (20%) to 3.3 MW (60%)) and flow conditions (10 % to 80 %). The sensitivity of different boiling parameters such as bubble departure diameter, nucleation site density, bubble departure frequency on the thermal hydraulic parameters was also studied. Flow instability has been observed at 20 % designed heat duty and 20 % flow conditions.

Keywords: thermal hydraulics, boiling, vapor fraction, sensitivity

Procedia PDF Downloads 124