Search results for: dissolution enhancement

Authors: Udit Mohanty, Mari Lundstrom

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Electrochemical investigation by cyclic voltammetry was conducted to explore the polarization behavior of reactions occurring in nickel electrowinning in presence of cationic impurities such as Ca2+ (0-100 mg/L), Na+ (1-10 g/L) and Mg2+ (10-100 mg/L). A comparative study was devised between industrial and synthetic electrolytes to observe the shift in the nucleation overpotentials of nickel deposition, dissolution and hydrogen evolution reactions at the cathode and anode respectively. Significant polarization of cathodic reactions were observed with concentrations of Na ≥ 8g /L and Ca ≤ 40 mg /L in the synthetic electrolytes. Nevertheless, a progressive increase in the concentration of Ca, Mg and Na in the industrial electrolyte demonstrated a depolarization behavior in the cathodic reactions related to nickel deposition and/or hydrogen evolution. Synergistic effect of Ca with Mg and Na in both the industrial and synthetic electrolytes induced a notable depolarization effect, also reflected in the peak currents.

Keywords: cationic impurities, cyclic voltammetry, electrowinning, nickel, polarization

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Authors: L. Belkhiri, L. Mouni, A. Tiri, T.S. Narany

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In the present study, the self-organizing map (SOM) clustering technique was applied to identify homogeneous clusters of hydrochemical parameters in El Milia plain, Algeria, to assess the quality of groundwater for potable and agricultural purposes. The visualization of SOM-analysis indicated that 35 groundwater samples collected in the study area were classified into three clusters, which showed progressive increase in electrical conductivity from cluster one to cluster three. Samples belonging to cluster one are mostly located in the recharge zone showing hard fresh water type, however, water type gradually changed to hard-brackish type in the discharge zone, including clusters two and three. Ionic ratio studies indicated the role of carbonate rock dissolution in increases on groundwater hardness, especially in cluster one. However, evaporation and evapotranspiration are the main processes increasing salinity in cluster two and three.

Keywords: groundwater quality, self-organizing maps, drinking water, irrigation water

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Authors: B. Z. Manuel, H. D. Esmeralda, H. S. Felipe, D. R. Héctor, D. de la Torre Sebastián, R. L. Diego

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Aluminum Matrix Composites reinforced with nanocrystalline Ni3Al carbon-coated intermetallic particles, were synthesized by powder metallurgy. Powder mixture of aluminum with 0.5-volume fraction of reinforcement particles was compacted by spark plasma sintering (SPS) technique and the compared with conventional sintering process. The better results for SPS technique were obtained in 520ºC-5kN-3min.The hardness (70.5±8 HV) and the elastic modulus (95 GPa) were evaluated in function of sintering conditions for SPS technique; it was found that the incorporation of these kind of reinforcement particles in aluminum matrix improve its mechanical properties. The densities were about 94% and 97% of the theoretical density. The carbon coating avoided the interfacial reaction between matrix-particle at high temperature (520°C) without show composition change either intermetallic dissolution.

Keywords: aluminum matrix composites, intermetallics, spark plasma sintering, nanocrystalline

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Authors: N. G. Margiani, I. G. Kvartskhava, G. A. Mumladze, Z. A. Adamia

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Chemical doping with different elements and compounds at various amounts represents the most suitable approach to improve the superconducting properties of bismuth-based superconductors for technological applications. In this paper, the influence of partial substitution of Sr(BO₂)₂ for SrO on the phase formation kinetics and transport properties of (Bi,Pb)-2223 HTS has been studied for the first time. Samples with nominal composition Bi_1.7Pb_0.3Sr_2-xCa₂Cu₃O_y[Sr(BO₂)₂]_x, x=0, 0.0375, 0.075, 0.15, 0.25, were prepared by the standard solid state processing. The appropriate mixtures were calcined at 845 ^oC for 40 h. The resulting materials were pressed into pellets and annealed at 837 ^oC for 30 h in air. Superconducting properties of undoped (reference) and Sr(BO₂)₂-doped (Bi,Pb)-2223 compounds were investigated through X-ray diffraction (XRD), resistivity (ρ) and transport critical current density (J_c) measurements. The surface morphology changes in the prepared samples were examined by scanning electron microscope (SEM). XRD and J_c studies have shown that the low level Sr(BO₂)₂ doping (x=0.0375-0.075) to the Sr-site promotes the formation of high-T_c phase and leads to the enhancement of current carrying capacity in (Bi,Pb)-2223 HTS. The doped sample with x=0.0375 has the best performance compared to other prepared samples. The estimated volume fraction of (Bi,Pb)-2223 phase increases from ~25 % for reference specimen to ~70 % for x=0.0375. Moreover, strong increase in the self-field J_c value was observed for this dopant amount (J_c=340 A/cm²), compared to an undoped sample (J_c=110 A/cm²). Pronounced enhancement of superconducting properties of (Bi,Pb)-2223 superconductor can be attributed to the acceleration of high-T_c phase formation as well as the improvement of inter-grain connectivity by small amounts of Sr(BO₂)₂ dopant.

Keywords: bismuth-based superconductor, critical current density, phase formation, Sr(BO₂)₂ doping

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Authors: Rui Du

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This paper attempts to assess the impact of a major sporting event —the Super Bowl on the local economies. The identification strategy is to compare the winning and losing cities at the National Football League (NFL) conference finals under the assumption of similar pre-treatment trends. The stock market performances of companies headquartered in these cities are used to capture the sudden changes in local economic activities during a short time span. The exogenous variations in the football game outcome allow a straightforward difference-in-differences approach to identify the effect. This study finds that the post-event trends in winning and losing cities diverge despite the fact that both cities have economically and statistically similar pre-event trends. Empirical analysis provides suggestive evidence of a positive, significant local economic impact of conference final wins, possibly through city image enhancement. Further empirical evidence shows the presence of heterogeneous effects across industrial sectors, suggesting that city image enhancing the effect of the Super Bowl participation is empirically relevant for the changes in the composition of local industries. Also, this study also adopts a similar strategy to examine the local economic impact of Super Bowl successes, however, finds no statistically significant effect.

Keywords: Super Bowl Participation, local economies, city image enhancement, difference-in-differences, industrial sectors

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Authors: Bimali Sanjeevani Weerakoon, Toshiaki Osuga, Takehisa Konishi

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Magnetic Resonance Imaging Contrast Agents (MRI-CM) are significant in the clinical and biological imaging as they have the ability to alter the normal tissue contrast, thereby affecting the signal intensity to enhance the visibility and detectability of images. Superparamagnetic Iron Oxide (SPIO) nanoparticles, coated with dextran or carboxydextran are currently available for clinical MR imaging of the liver. Most SPIO contrast agents are T2 shortening agents and Resovist (Ferucarbotran) is one of a clinically tested, organ-specific, SPIO agent which has a low molecular carboxydextran coating. The enhancement effect of Resovist depends on its relaxivity which in turn depends on factors like magnetic field strength, concentrations, nanoparticle properties, pH and temperature. Therefore, this study was conducted to investigate the impact of field strength and different contrast concentrations on enhancement effects of Resovist. The study explored the MRI signal intensity of Resovist in the physiological range of plasma from T2-weighted spin echo sequence at three magnetic field strengths: 0.47 T (r1=15, r2=101), 1.5 T (r1=7.4, r2=95), and 3 T (r1=3.3, r2=160) and the range of contrast concentrations by a mathematical simulation. Relaxivities of r1 and r2 (L mmol-1 Sec-1) were obtained from a previous study and the selected concentrations were 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, and 3.0 mmol/L. T2-weighted images were simulated using TR/TE ratio as 2000 ms /100 ms. According to the reference literature, with increasing magnetic field strengths, the r1 relaxivity tends to decrease while the r2 did not show any systematic relationship with the selected field strengths. In parallel, this study results revealed that the signal intensity of Resovist at lower concentrations tends to increase than the higher concentrations. The highest reported signal intensity was observed in the low field strength of 0.47 T. The maximum signal intensities for 0.47 T, 1.5 T and 3 T were found at the concentration levels of 0.05, 0.06 and 0.05 mmol/L, respectively. Furthermore, it was revealed that, the concentrations higher than the above, the signal intensity was decreased exponentially. An inverse relationship can be found between the field strength and T2 relaxation time, whereas, the field strength was increased, T2 relaxation time was decreased accordingly. However, resulted T2 relaxation time was not significantly different between 0.47 T and 1.5 T in this study. Moreover, a linear correlation of transverse relaxation rates (1/T2, s–1) with the concentrations of Resovist can be observed. According to these results, it can conclude that the concentration of SPIO nanoparticle contrast agents and the field strengths of MRI are two important parameters which can affect the signal intensity of T2-weighted SE sequence. Therefore, when MR imaging those two parameters should be considered prudently.

Keywords: Concentration, resovist, field strength, relaxivity, signal intensity

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Authors: Agustine Melviana, Rizkita Esyanti

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Stevia plant contains steviol glycosides which is estimated to be 300 times sweeter than sucrose. However in Indonesia, conventional (in vivo) propagation of Stevia rebaudiana was not effective due to a poor result. Therefore, alternative methods to propagate S. rebaudiana plants is needed, one of it is using in vitro method. Multiplication with a large quantity of stevia biomass in relatively short period can be conducted by using TIS RITA® (Recipient for Automated Temporary Immersion System). The objective of this study was to evaluate the effect of immersion period of the medium on growth and the medium bioconversion into the production of shoot biomass. The study was conducted to determine the effect of different intensity period of medium to enhance biomass of stevia shoots. Shoot culture of S. rebaudiana was grown in full strength MS medium supplemented with 1 ppm Kinetin. RITA® bioreactors were set up with two different immersion periods, 15 min (RITA® 15) and 30 min (RITA® 30), scheduled every 6 hours and incubated for 21 days. The result indicated that immersion period affected the biomass and growth rate (µ). Thirty-minutes immersion showed greater percentage of shoot multiplication (93.44 ± 0.83%), percentage of leaf growth (85.24 ± 5.99%), growth rate (0.042 ± 0.001 g/day), and productivity (0.066 g/L medium/day) compared to that immersed in RITA® 15 min (76.90 ± 4.85%; 79.73 ± 7.76; 0.045 ± 0.004 g/day, and 0.045 g/L medium/day respectively). Enhancement of biomass in RITA® 30 reached 1,702 ± 0,114 gr, whereas in RITA® 15 only 0,953 ± 0,093 gr. Additionally, the pattern of sucrose, mineral, and inorganic compounds consumption followed the growth of plant biomass for both systems. In conclusion, the bioconversion efficiency from medium to biomass in RITA® 30 is better than RITA® 15.

Keywords: intensity period, shoot culture, Stevia rebaudiana, TIS RITA®

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Authors: Betsy S. Thomas, Manjeet Marpara, K. M. Bhat

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Introduction: After the initial enthusiasm and interest in hydroxyapatite products subsided due to dissolution of the coating and failure at the coating interface, this was a unique attempt to create a next generation of dental implant. Materials and Methods: The adhesion property of AW and HA coatings at various temperature by pulsed laser deposition was assessed on titanium plates. Moreover, AW/HA coated implants implanted in the femur of the rabbits was evaluated at various intervals. Results: Decohesion load was more for AW in scratch test and more bone formation around AW coated implants on histological evaluation. Discussion: AW coating by pulsed laser deposition was more adherent to the titanium surface and led to faster bone formation than HA. Conclusion: This experiment opined that AW coated by pulsed laser deposition seems to be a promising method in achieving bioactive coatings on titanium implants.

Keywords: surface coating, dental implants, osseo integration, biotechnology

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Authors: Jason Ting Jing Cheng, Lee Foo Wei, Yew Ming Kun, Chin Ren Jie, Yip Chun Chieh

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The utilization of industrial by-products, such as steel slag in cementitious materials, not only mitigates environmental impact but also enhances material properties. This study investigates the dual influence of steel slag particle size on the compressive strength and carbonation efficiency of cementitious composites. Through a systematic experimental approach, steel slag particles were incorporated into cement at varying sizes, and the resulting composites were subjected to mechanical and carbonation tests. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are conducted in this paper. The findings reveal a positive correlation between increased particle size and compressive strength, attributed to the improved interfacial transition zone and packing density. Conversely, smaller particle sizes exhibited enhanced carbonation efficiency, likely due to the increased surface area facilitating the carbonation reaction. The presence of higher silica and calcium content in finer particles was confirmed by EDX, which contributed to the accelerated carbonation process. This study underscores the importance of particle size optimization in designing sustainable cementitious materials with balanced mechanical performance and carbon sequestration potential. The insights gained from the advanced analytical techniques offer a comprehensive understanding of the mechanisms at play, paving the way for the strategic use of steel slag in eco-friendly construction practices.

Keywords: steel slag, carbonation efficiency, particle size enhancement, compressive strength

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Authors: Deokyeong Choe, Jae Eun Nam, Young Hoon Roh, Chul Soo Shin

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The development of hydrogels with a high mechanical strength is important for numerous applications of hydrogels. As a material for tough hydrogels, cellulose has attracted much interest. However, cellulose cannot be melted and is very difficult to be dissolved in most solvents. Therefore, its dissolution in tetrabutylammonium fluoride/dimethyl sulfoxide (TBAF/DMSO) solvents has attracted researchers for chemical processing of cellulose. For this reason, studies about rheological properties of cellulose/TBAF/DMSO solution will provide useful information. In this study, viscosities of cellulose solutions prepared using different amounts of cellulose and TBAF in DMSO were measured. As expected, the viscosity of cellulose solution decreased with respect to the increasing volume of DMSO. The most viscose cellulose solution was achieved at a 1:1 mass ratio of cellulose to TBAF regardless of their contents in DMSO. At a 1:1 mass ratio of cellulose to TBAF, the formation of cellulose nanoparticles (467 nm) resulted in a dramatic increase in the viscosity, which led to the fabrication of 3D cellulose hydrogels.

Keywords: cellulose, TBAF/DMSO, viscosity, hydrogel

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Authors: Ghulam Muhammad Ali

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Unveiling of genes involved in drought and root architecture using transcriptomic analyses remained fragmented for further improvement of wheat through genome editing. The purpose of this research endeavor was to unveil the variations in different genes implicated in drought tolerance and root architecture in wheat through RNA-seq data analysis. In this study seedlings of 8 days old, 6 cultivars of wheat namely, Batis, Blue Silver, Local White, UZ888, Chakwal 50 and Synthetic wheat S22 were subjected to transcriptomic analysis for root and shoot genes. Total of 12 RNA samples was sequenced by Illumina. Using updated wheat transcripts from Ensembl and IWGC references with 54,175 gene models, we found that 49,621 out of 54,175 (91.5%) genes are expressed at an RPKM of 0.1 or more (in at least 1 sample). The number of genes expressed was higher in Local White than Batis. Differentially expressed genes (DEG) were higher in Chakwal 50. Expression-based clustering indicated conserved function of DRO1and RPK1 between Arabidopsis and wheat. Dendrogram showed that Local White is sister to Chakwal 50 while Batis is closely related to Blue Silver. This study flaunts transcriptomic sequence variations in different cultivars that showed mutations in genes associated with drought that may directly contribute to drought tolerance. DRO1 and RPK1 genes were fetched/isolated for genome editing. These genes are being edited in wheat through CRISPR-Cas9 for yield enhancement.

Keywords: transcriptomic, wheat, genome editing, drought, CRISPR-Cas9, yield enhancement

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Authors: Modreck Gomo

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Although the dolomite and calcite carbonates can neutralize Acid Mine Drainage (AMD) and prevent leaching of metals, salinity still remains a huge problem. The study presents a conceptual discussion of geochemical controls of salinity in a typical calcite and dolomite AMD neutralised groundwater systems. Thereafter field evidence is presented to support the conceptual discussions. 1020 field data sets of from a groundwater system reported to be under circumneutral conditions from the neutralization effect of calcite and dolomite is analysed using correlation analysis and bivariate plots. Field evidence indicates that sulphate, calcium and magnesium are strongly and positively correlated to Total Dissolved Solids (TDS) which is used as measure of salinity. In this, a hydrogeochemical system, the dissolution of sulphate, calcium and magnesium form AMD neutralization process contributed 50%, 10% and 5% of the salinity.

Keywords: acid mine drainage, carbonates, neutralization, salinity

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Authors: Sanjay Singh, Parameswara Rao Vuddanda

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The aim of the present study is study the factual benefit of nano size and surface coating of p-gp efflux inhibitor on enhancement of bioavailability of Berberine chloride (BBR); a p-gp substrate. In addition, 28 days sub acute oral toxicity study was also conducted to assess the toxicity of the formulation on chronic administration. BBR loaded polymeric nanoparticles (BBR-NP) were prepared by nanoprecipitation method. BBR NP were surface coated (BBR-SCNP) with the 1 % w/v of vitamin E TPGS. For bioavailability study, total five groups (n=6) of rat were treated as follows first; pure BBR, second; physical mixture of BBR, carrier and vitamin E TPGS, third; BBR-NP, fourth; BBR-SCNP and fifth; BBR and verapamil (widely used p-gp inhibitor). Blood was withdrawn at pre-set timing points in 24 hrs study and drug was quantified by HPLC method. In oral chronic toxicity study, total four groups (n=6) were treated as follows first (control); water, second; pure BBR, third; BBR surface coated nanoparticles and fourth; placebo BBR surface coated nanoparticles. Biochemical levels of liver (AST, ALP and ALT) and kidney (serum urea and creatinine) along with their histopathological studies were also examined (0-28 days). The AUC of BBR-SCNP was significantly 3.5 folds higher compared to all other groups. The AUC of BBR-NP was 3.23 and 1.52 folds higher compared to BBR solution and BBR with verapamil group, respectively. The physical mixture treated group showed slightly higher AUC than BBR solution treated group but significantly low compared to other groups. It indicates that encapsulation of BBR in nanosize form can circumvent P-gp efflux effect. BBR-NP showed pharmacokinetic parameters (Cmax and AUC) which are near to BBR-SCNP. However, the difference in values of T1/2 and clearance indicate that surface coating with vitamin E TPGS not only avoids the P-gp efflux at its absorption site (intestine) but also at organs which are responsible for metabolism and excretion (kidney and liver). It may be the reason for observed decrease in clearance of BBR-SCNP. No toxicity signs were observed either in biochemical or histopathological examination of liver and kidney during toxicity studies. The results indicate that administration of BBR in surface coated nanoformulation would be beneficial for enhancement of its bioavailability and longer retention in systemic circulation. Further, sub acute oral dose toxicity studies for 28 days such as evaluation of intestine, liver and kidney histopathology and biochemical estimations indicated that BBR-SCNP developed were safe for long use.

Keywords: bioavailability, berberine nanoparticles, p-gp efflux inhibitor, nanoprecipitation method

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Authors: Mohamed Ben Amar, Henda Barhoumi, Hokia Siala, Foued Elhalouani

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The present contribution consists of a purely experimental investigation on the effect of Squeeze casting on the micro structural and mechanical propriety of Al-Si alloys destined to automotive industry. Accordingly, we have proceeding, by ourselves, to all the thermal treatment consisting of solution treatment at 540°C for 8h and aging at 160°C for 4h. The various thermal treatment, have been carried out in order to monitor the processes of formation and dissolution accompanying the solid state phase transformations as well as the resulting changes in the mechanical proprieties. The examination of the micrographs of the aluminum alloys reveals the dominant presence of dendrite. Concerning the mechanical characteristic the Vickers micro-hardness curve an increase as a function of the pressure. As well as the heat treatment increase mechanical propriety such that pressure and micro hardness. The curves have been explained in terms of structural hardening resulting from the various compounds formation.

Keywords: squeeze casting, process parameters, heat treatment, ductility, microstructure

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Authors: Ibrahim Auwal

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This study focuses on senior secondary education towards the development of younger generation in general terms, and specifically for the enhancement of senior secondary school principals. Investigation was made to correlate between principals’ application of basic principles of educational administration and principals’ productivity in senior secondary schools in Kano State. The instrument used to collect relevant data was self designed Observation Inventory for School Principals (OISP). The observation inventory items were scrutinized by experts from the School of Education Federal College of Education Kano to ascertain the contents validity, and the reliability coefficient was 0.83. Using purposive sampling technique, 30 schools were chosen from 85 senior secondary schools in Kano state and 30 principals were deliberately sampled due to their small number. Pearson Product Moment Correlation (r) Coefficient was used to test the hypothesis generated for the study. The results of the analysis showed that principals’ application of basic principles of educational administration was significantly correlated with principals’ productivity and it promote the performance of the students. Based on the findings, it was recommended that, government should in as much as possible encourage school principals to obtain degrees in relevant and specialized areas in education specifically educational administration and planning so as to get all the necessary knowledge and skills of leader ship procedures that will definitely promote teachers morale, improve students’ academic performance and enhances principals’ productivity in senior secondary schools in Kano State.

Keywords: principles of educational administration, principals of senior secondary schools, Kano, educational sciences

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Authors: E. Poupelloz, S. Gauffinet

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Ettringite Ca₆Al₂(SO₄)₃(OH)₁₂26H₂O is one of the major hydrates formed during cement hydration. Ettringite forms in Portland cement from the reaction between tricalcium aluminate Ca₃Al₂O₆ and calcium sulfate. Ettringite is also present in calcium sulfoaluminate cement in which it is the major hydrate, formed by the reaction between yeelimite Ca₄(AlO₂)₆SO₄ and calcium sulfate. About the formation of ettringite, numerous results are available in the literature even if some issues are still under discussion. However, almost all published work about ettringite was done on cementitious systems. Yet in cement, hydration reactions are very complex, the result of dissolution-precipitation processes and are submitted to various interactions. Understanding the formation process of a phase alone, here ettringite, is the first step to later understand the much more complex reactions happening in cement. This study is crucial for the comprehension of early cement hydration and physical behavior. Indeed formation of hydrates, in particular, ettringite, will have an influence on the rheological properties of the cement paste and on the need for admixtures. To make progress toward the understanding of existing phenomena, a specific study of nucleation and growth processes of ettringite was conducted. First ettringite nucleation was studied in ionic aqueous solutions, with controlled but different experimental conditions, as different supersaturation degrees (β), different pH or presence of exogenous ions. Through induction time measurements, interfacial ettringite crystals solution energies (γ) were determined. Growth of ettringite in supersaturated solutions was also studied through chain crystallization reactions. Specific BET surface area measurements and Scanning Electron Microscopy observations seemed to prove that growth process is favored over the nucleation process when ettringite crystals are initially present in a solution with a low supersaturation degree. The influence of stirring on ettringite formation was also investigated. Observation was made that intensity and nature of stirring have a high influence on the size of ettringite needles formed. Needle sizes vary from less than 10µm long depending on the stirring to almost 100µm long without any stirring. During all previously mentioned experiments, initially present ions are consumed to form ettringite in such a way that the supersaturation degree with regard to ettringite is decreasing over time. To avoid this phenomenon a device compensating the drop of ion concentrations by adding some more solutions, and therefore always have constant ionic concentrations, was used. This constant β recreates the conditions of the beginning of cement paste hydration, when the dissolution of solid reagents compensates the consumption of ions to form hydrates. This device allowed the determination of the ettringite precipitation rate as a function of the supersaturation degree β. Taking samples at different time during ettringite precipitation and doing BET measurements allowed the determination of the interfacial growth rate of ettringite in m²/s. This work will lead to a better understanding and control of ettringite formation alone and thus during cements hydration. This study will also ultimately define the impact of ettringite formation process on the rheology of cement pastes at early age, which is a crucial parameter from a practical point of view.

Keywords: cement hydration, ettringite, morphology of crystals, nucleation-growth process

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Authors: R. Blythman, N. Jeffers, T. Persoons, D. B. Murray

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The exploitation of flow pulsation in micro- and mini-channels is a potentially useful technique for enhancing cooling of high-end photonics and electronics systems. It is thought that pulsation alters the thickness of the hydrodynamic and thermal boundary layers, and hence affects the overall thermal resistance of the heat sink. Although the fluid mechanics and heat transfer are inextricably linked, it can be useful to decouple the parameters to better understand the mechanisms underlying any heat transfer enhancement. Using two-dimensional, two-component particle image velocimetry, the current work intends to characterize the heat transfer mechanisms in pulsating flow with a mean Reynolds number of 48 by experimentally quantifying the hydrodynamics of a generic liquid-cooled channel geometry. Flows circulated through the test section by a gear pump are modulated using a controller to achieve sinusoidal flow pulsations with Womersley numbers of 7.45 and 2.36 and an amplitude ratio of 0.75. It is found that the transient characteristics of the measured velocity profiles are dependent on the speed of oscillation, in accordance with the analytical solution for flow in a rectangular channel. A large velocity overshoot is observed close to the wall at high frequencies, resulting from the interaction of near-wall viscous stresses and inertial effects of the main fluid body. The steep velocity gradients at the wall are indicative of augmented heat transfer, although the local flow reversal may reduce the upstream temperature difference in heat transfer applications. While unsteady effects remain evident at the lower frequency, the annular effect subsides and retreats from the wall. The shear rate at the wall is increased during the accelerating half-cycle and decreased during deceleration compared to steady flow, suggesting that the flow may experience both enhanced and diminished heat transfer during a single period. Hence, the thickness of the hydrodynamic boundary layer is reduced for positively moving flow during one half of the pulsation cycle at the investigated frequencies. It is expected that the size of the thermal boundary layer is similarly reduced during the cycle, leading to intervals of heat transfer enhancement.

Keywords: Heat transfer enhancement, particle image velocimetry, localized and time-resolved velocity, photonics and electronics cooling, pulsating flow, Richardson’s annular effect

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Authors: Pooyan Changizian, Zhongwen Yao

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The purpose of current study is to make an excellent correlation between mechanical properties and microstructures of ion irradiated X-750 Ni-based superalloy. Towards this end, two different irradiation procedures were carried out, including single Ni ion irradiation and pre-helium implantation with subsequent Ni ion irradiation. Nano-indentation technique was employed to evaluate the mechanical properties of irradiated material. The nano-hardness measurements depict highly different results for two irradiation procedures. Single ion irradiated X-750 shows softening behavior; however, pre-helium implanted specimens present significant hardening compared to the un-irradiated material. Cross-section TEM examination demonstrates that softening is attributed to the γ׳-precipitate instability (disordering/dissolution) which overcomes the hardening effect of irradiation-induced defects. In contrast, the presence of cavities or helium bubbles is probably the main cause for irradiation-induced hardening of helium implanted samples.

Keywords: Inconel X-750, nanoindentation, helium bubbles, defects

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Authors: Ayman Othman, Tallat Ali

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The successive increase of generated waste materials like glass has led to many environmental problems. Using crushed waste glass in hot mix asphalt paving has been though as an alternative to landfill disposal and recycling. This paper discusses the possibility of utilizing crushed waste glass, as a part of fine aggregate in hot mix asphalt in Egypt. This is done through evaluation of the mechanical properties of asphalt concrete mixtures mixed with waste glass and determining the appropriate glass content that can be adapted in asphalt pavement. Four asphalt concrete mixtures with various glass contents, namely; 0%, 4%, 8% and 12% by weight of total mixture were studied. Evaluation of the mechanical properties includes performing Marshall stability, indirect tensile strength, fracture energy and unconfined compressive strength tests. Laboratory testing had revealed the enhancement in both compressive strength and Marshall stability test parameters when the crushed glass was added to asphalt concrete mixtures. This enhancement was accompanied with a very slight reduction in both indirect tensile strength and fracture energy when glass content up to 8% was used. Adding more than 8% of glass causes a sharp reduction in both indirect tensile strength and fracture energy. Testing results had also shown a reduction in the optimum asphalt content when the waste glass was used. Measurements of the heat loss rate of asphalt concrete mixtures mixed with glass revealed their ability to hold heat longer than conventional mixtures. This can have useful application in asphalt paving during cold whether or when a long period of post-mix transportation is needed.

Keywords: waste glass, hot mix asphalt, mechanical performance, indirect tensile strength, fracture energy, compressive strength

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Authors: Houda Kohli Kallel, Soumaya Gharsallah Falhi

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Kerkennah Islands are a group of islands lying off the eastern coast of Tunisia, 15 miles from the Sfaxian coast. This archipelago covers an area of 150 square kilometres, and it consists of two main islands : The Gharbi and The Chergui . It also covers twelve more islets. Kerkennah is endowed with an exceptional cultural, natural and ecological potential, essential for the sustainability of the island community. Hence ,the inhabitants there have mobilized the natural resources of their land for decades. However, today, and despite these heritage treasures, Kerkennian islanders are facing social, economic and environmental challenges which are currently hindering the development of the traditional activities of fishing and farming. Other than being isolated and having a non-diversified economy, we cite the erosion of the stream banks, the exodus of young people and the population aging. "This study find the solutions that are likely to allow a sustainable development of the island territory, its enhancement and the strengthening of its identity. It is also necessary to study the key factors impacting the archipelago’s cultural tourism of decision makers and citizens. First, we will present the archipelago. Second, we will describe its tangible as well as intangible heritage. Then, we will present the new modes of the site exploitation. Finally, we will identify some new projects paving the way to a sustainable tourism in Kerkennah such as Borj EL Lahssar archaeological digs and Kerkennah insular heritage museum. To conclude, the archipelago of Kerkennah needs to reintegrate all its historical, architectural and archaeological assets in order to enhance its cultural tourism based on the cultural circuits of the territorial identities and the island values.

Keywords: kerkennah, identity, heritage, historical architectural

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Authors: I. A. Ibrahim, T. A. Elbarbary, N. Abdelaty, A. T. Kandil, H. K. Farhan

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The present work aims to study the leaching of Abu Ghalaga ilmenite ore by hydrochloric acid and simultaneous reduction by iron powder method to dissolve its titanium and iron contents. Iron content in the produced liquor is separated by solvent extraction using TBP as a solvent. All parameters affecting the efficiency of the dissolution process were separately studied including the acid concentration, solid/liquid ratio which controls the ilmenite/acid molar ratio, temperature, time and grain size. The optimum conditions at which maximum leaching occur are 30% HCl acid with a solid/liquid ratio of 1/30 at 80 °C for 4 h using ore ground to -350 mesh size. At the same time, all parameters affecting on solvent extraction and stripping of iron content from the produced liquor were studied. Results show that the best extraction is at solvent/solution 1/1 by shaking at 240 RPM for 45 minutes at 30 °C whereas best striping of iron at H₂O/solvent 2/1.

Keywords: ilmenite ore, leaching, titanium solvent extraction, Abu Ghalaga ilmenite ore

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Authors: Surajj Sarode, G. P. Vadnere, G. Vidya Sagar

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Compression coating is one of the strategies for delivering drug to the colon based on Gastrointestinal PH and transit time concept. The main aim of these formulations to develop rapidly disintegrating Zaltoprofen core tablets compression-coated with a mixture of time-dependent hydrophilic swellable polymer HPMC K 15 and PH responsive soluble polymer Chitosan and Guar gum in different ratios. The effect of the proportion of HPMC, Chitosan and Guar gum in the coat on premature drug release in upper part (Stomach and small intestine) of GIT and the amount of drug release in colon target area was studied. The formulations are carried out by using Direct Compression method. Sodium starch Glycolate used for rapid disintegration. FTIR used for Drug-Polymer Interaction studies. The prepared tablets were evaluated for hardness, thickness, friability, in-vitro disintegration, in-Vitro dissolution and in-vitro kinetic study.

Keywords: zaltoprofen, chitosan, formulation, drug delivery

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Authors: Jiahui You, Kyung Jae Lee

Abstract:

Hydraulic fracturing fluid (HFF) is widely used in shale reservoir productions. HFF contains diverse chemical additives, which result in the dissolution and precipitation of minerals through multiple chemical reactions. In this study, a new pore-scale Darcy–Brinkman–Stokes (DBS) model coupled with Level Set Method (LSM) is developed to address the microscopic phenomena occurring during the iron–HFF interaction, by numerically describing mass transport, chemical reactions, and pore structure evolution. The new model is developed based on OpenFOAM, which is an open-source platform for computational fluid dynamics. Here, the DBS momentum equation is used to solve for velocity by accounting for the fluid-solid mass transfer; an advection-diffusion equation is used to compute the distribution of injected HFF and iron. The reaction–induced pore evolution is captured by applying the LSM, where the solid-liquid interface is updated by solving the level set distance function and reinitialized to a signed distance function. Then, a smoothened Heaviside function gives a smoothed solid-liquid interface over a narrow band with a fixed thickness. The stated equations are discretized by the finite volume method, while the re-initialized equation is discretized by the central difference method. Gauss linear upwind scheme is used to solve the level set distance function, and the Pressure–Implicit with Splitting of Operators (PISO) method is used to solve the momentum equation. The numerical result is compared with 1–D analytical solution of fluid-solid interface for reaction-diffusion problems. Sensitivity analysis is conducted with various Damkohler number (DaII) and Peclet number (Pe). We categorize the Fe (III) precipitation into three patterns as a function of DaII and Pe: symmetrical smoothed growth, unsymmetrical growth, and dendritic growth. Pe and DaII significantly affect the location of precipitation, which is critical in determining the injection parameters of hydraulic fracturing. When DaII<1, the precipitation uniformly occurs on the solid surface both in upstream and downstream directions. When DaII>1, the precipitation mainly occurs on the solid surface in an upstream direction. When Pe>1, Fe (II) transported deeply into and precipitated inside the pores. When Pe<1, the precipitation of Fe (III) occurs mainly on the solid surface in an upstream direction, and they are easily precipitated inside the small pore structures. The porosity–permeability relationship is subsequently presented. This pore-scale model allows high confidence in the description of Fe (II) dissolution, transport, and Fe (III) precipitation. The model shows fast convergence and requires a low computational load. The results can provide reliable guidance for injecting HFF in shale reservoirs to avoid clogging and wellbore pollution. Understanding Fe (III) precipitation, and Fe (II) release and transport behaviors give rise to a highly efficient hydraulic fracture project.

Keywords: reactive-transport , Shale, Kerogen, precipitation

Procedia PDF Downloads 147

Authors: Mohamed El Morsy, Gabriela Achtenová

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Condition monitoring is used to increase machinery availability and machinery performance, whilst reducing consequential damage, increasing machine life, reducing spare parts inventories, and reducing breakdown maintenance. An efficient condition monitoring system provides early warning of faults by predicting them at an early stage. When a localized fault occurs in gears, the vibration signals always exhibit non-stationary behavior. The periodic impulsive feature of the vibration signal appears in the time domain and the corresponding gear mesh frequency (GMF) emerges in the frequency domain. However, one limitation of frequency-domain analysis is its inability to handle non-stationary waveform signals, which are very common when machinery faults occur. Particularly at the early stage of gear failure, the GMF contains very little energy and is often overwhelmed by noise and higher-level macro-structural vibrations. An effective signal processing method would be necessary to remove such corrupting noise and interference. In this paper, a new hybrid method based on optimal Morlet wavelet filter and autocorrelation enhancement is presented. First, to eliminate the frequency associated with interferential vibrations, the vibration signal is filtered with a band-pass filter determined by a Morlet wavelet whose parameters are selected or optimized based on maximum Kurtosis. Then, to further reduce the residual in-band noise and highlight the periodic impulsive feature, an autocorrelation enhancement algorithm is applied to the filtered signal. The test stand is equipped with three dynamometers; the input dynamometer serves as the internal combustion engine, the output dynamometers induce a load on the output joint shaft flanges. The pitting defect is manufactured on the tooth side of a gear of the fifth speed on the secondary shaft. The gearbox used for experimental measurements is of the type most commonly used in modern small to mid-sized passenger cars with transversely mounted powertrain and front wheel drive: a five-speed gearbox with final drive gear and front wheel differential. The results obtained from practical experiments prove that the proposed method is very effective for gear fault diagnosis.

Keywords: wavelet analysis, pitted gear, autocorrelation, gear fault diagnosis

Procedia PDF Downloads 367

Authors: Mohamed A. Deyab, Ahmed E. Awadallah

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Under various conditions, we present a promising method for producing pure hydrogen energy from the electrochemical reaction of Mg metal in waste oilfield water (WOW). Mg metal and WOW are primarily consumed in this process. The results show that the hydrogen gas output is highly dependent on temperature and solution pH. The best conditions for hydrogen production were found to be a low pH (2.5) and a high temperature (338 K). For the first time, the Allyl methylimidazolium bis-trifluoromethyl sulfonyl imide) (IL) ionic liquid is used to regulate the rate of hydrogen generation. It has been confirmed that increasing the solution temperature and decreasing the solution pH accelerates Mg dissolution and produces more hydrogen per unit of time. The adsorption of IL on the active sites of the Mg surface is unrestricted by mixing physical and chemical orientation. Inspections using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and FT-IR spectroscopy were used to identify and characterise surface corrosion of Mg in WOW. This process is also completely safe and can create energy on demand.

Keywords: hydrogen production, Mg, wastewater, ionic liquid

Procedia PDF Downloads 132

Authors: Swati Bishnoi, D. Haranath, Vinay Gupta

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In this work, we demonstrate that the power conversion efficiency (PCE) of organic solar cells (OSCs) could be improved significantly by using ZnO doped with Aluminum (Al) and Europium (Eu) as cathode buffer layer (CBL). The ZnO:Al,Eu nanoparticle layer has broadband absorption in the ultraviolet (300-400 nm) region. The Al doping contributes to the enhancement in the conductivity whereas Eu doping significantly improves emission in the visible region. Moreover, this emission overlaps with the absorption range of polymer poly [N -9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′- benzothiadiazole)] (PCDTBT) significantly and results in an enhanced absorption by the active layer and hence high photocurrent. An increase in the power conversion efficiency (PCE) of 6.8% has been obtained for ZnO: Al,Eu CBL as compared to 5.9% for pristine ZnO, in the inverted device configuration ITO/CBL/active layer/MoOx/Al. The active layer comprises of a blend of PCDTBT donor and [6-6]-phenyl C71 butyric acid methyl ester (PC71BM) acceptor. In the reference device pristine ZnO has been used as CBL, whereas in the other one ZnO:Al,Eu has been used as CBL. The role of the luminescent CBL layer is to down-shift the UV light into visible range which overlaps with the absorption of PCDTBT polymer, resulting in an energy transfer from ZnO:Al,Eu to PCDTBT polymer and the absorption by active layer is enhanced as revealed by transient spectroscopy. This enhancement resulted in an increase in the short circuit current which contributes in an increased PCE in the device employing ZnO: Al,Eu CBL. Thus, the luminescent ZnO: Al, Eu nanoparticle CBL has great potential in organic solar cells.

Keywords: cathode buffer layer, energy transfer, organic solar cell, power conversion efficiency

Procedia PDF Downloads 232

Authors: Fadwa Jewilli

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A sudden leak of a 6-inch gas line pipe after being in service for one year was observed. The pipe had been designed to transport dry gas. The failure had taken place in 6 o’clock position at the stage discharge of the flow process. Laboratory investigations were conducted to find out the cause of the pipe rupture. Visual and metallographic observations confirmed that the pipe split was due to a crack initiated in circumferential and then turned into longitudinal direction. Sever wall thickness reduction was noticed on the internal pipe surface. Scanning electron microscopy observations at the fracture surface revealed features of ductile fracture mode. Corrosion product analysis showed the traces of iron carbonate and iron sulphate. The laboratory analysis resulted in the conclusion that the pipe failed due to the effect of wet fluid (condensate) caused severe wall thickness dissolution resulted in pipe could not stand the continuation at in-service working condition.

Keywords: gas line pipe, corrosion prediction ductile fracture, ductile fracture, failure analysis

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Authors: Nisrine Benzbiria, Mohammed Azzi, Mustapha Zertoubi

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2XXX series of aluminum alloys are widely employed in several applications, such as beverages, automotive, and aerospace industries. However, they are particularly prone to localized corrosion, such as pitting, often induced by a difference in corrosion potential measured for intermetallic phases and pure metal. The galvanic cells comprising Al–Cu– Mn–Fe intermetallic phases control cathodically the dissolution rate as oxygen reduction reaction kinetics are privileged on Al–Cu–Mn–Fe particles. Hence, understanding the properties of cathode sites and the processes involved must be carried out. Our interest is to outline the cathodic behavior of AA2024-T3 in sodium sulfate solution using electrochemical techniques. Oxygen reduction reaction (ORR) was investigated in the mixed charge transfer and mass transport regime using the Koutecky-Levich approach. An environmentally benign inhibitor was considered to slow the ORR on the Cu-rich cathodic phases. The surface morphology of the electrodes was investigated with SEM/EDS and AFM. The obtained results were discussed accordingly.

Keywords: AA2024-T3, neutral medium, ORR kinetics, Koutecky-Levich, DFT

Procedia PDF Downloads 27

Authors: Mario G. Rodriguez

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This paper undertakes an in-depth exploration of David Cronenberg's filmography through Jean Baudrillard's theory of simulacra and simulation. Little has been written to show how Cronenberg’s cinema exemplifies Baudrillard’s conceptualization of postmodernity. The study employs Baudrillard’s historical orders of simulacra, as well as his definitions of hyperreality and simulation, to recontextualize Cronenberg’s films in an era characterized by the increasing influence of media and technology and Cronenberg's oeuvre presents a compelling canvas for examining the interplay between the real and the simulated. Through films like "Videodrome" (1983), "The Fly" (1986), and "eXistenZ" (1999), Cronenberg navigates the complex terrain of the human body, technology, and societal perceptions, echoing Baudrillard's concerns about the hyperreal and the dissolution of reality. The study concludes with a consideration of the role of "body-horror" as it pertains to Baudrillard's theory. It sheds light on how fear of loss of bodily autonomy, the relationship between technology and the human body, and the intersection of science, medicine, and horror reflect the nature of hyperreality and simulation.

Keywords: Cronenberg, hyperreality, simulation, Baudrillard

Procedia PDF Downloads 45

Authors: Nurcan Tugrul, Funda Demir, Hilal Ozkan, Nur Olgun, Emek Derun

Abstract:

Geopolymers are aluminosilicate-containing materials. The raw materials of the geopolymerization can be natural material such as kaolinite, metakaolin (calcined kaolinite), clay, diatomite, rock powder or can also be industrial by-products such as fly ash, silica fume, blast furnace slag, rice-husk ash, mine tailing, red mud, waste slag, etc. Reactivity of raw materials in geopolymer production is very important for achieving high reaction grade. Fly ash used in geopolymer production has been calcined to obtain tetrahedral SiO₂ and Al₂O₃ structures. In this study, fly ash calcined at different temperatures (700, 800 and 900 °C), and Al₂O₃ addition (Al₂O₃ at min (0%) and max (100%)) were used to produce geopolymers. HCl dissolution method was applied to determine the geopolymerization percentage of samples and Fourier Transform Infrared (FTIR) Spectroscopy was used to find out the optimum calcination temperature for geopolymerization. According to obtained results, the highest geopolymerization percentage (0% alumina added geopolymer equal to 35.789%; 100% alumina added geopolymer equal to 40.546%) was obtained in samples using fly ash calcined at 800 °C.

Keywords: geopolymer, fly ash, Al₂O₃ addition, calcination

Procedia PDF Downloads 158