1,720,959 research outputs found
Simulation and Experimental Validation of Hydrogen Evolution Reaction using Titanium Carbide Supported, Platinum Doped Tetrahedral Amorphous Carbon Electrode
Get PDFThis work presented the use of commercial software COMSOL Multiphysics to simulate and solve the Volmer - Heyrovsky –Tafel mechanistic steps for hydrogen evolution reaction (HER). The first study will address the reliability of COMSOL to provide accurate and precise results for electrochemistry problem. The developed model is for classical cyclic voltammetry of redox reaction (E). In this study, mesh refinement with its consequent number of elements (noe), computation time (tcom), and current, I(t) was compared on the 1-dimension (1D), 2-dimension (2D) axisymmetric, and 3-dimension (3D) model. This study proved the software's consistency to produce less than 3% error between simulation and analytical results across all dimensions. By using a relative tolerance (rtol) value of 1×10-8 with very concentrated custom meshing, a 3D model yielded a result with an error of 2.5% compared to analytical solution. It has the drawback of taking 40 times longer to complete. A slight discrepancy between 2D axisymmetric and 3D simulation results on finest meshing recorded to have less than 3% difference due to CPU memory limit. The use of adaptive meshing on 2D axisymmetric and 3D model with coarse initial mesh reduces the error significantly by 32% and 50%, respectively. At the same time, the computation time, tcom increased by nearly ten times on the 2D axisymmetric model and five times on the 3D model. On the “finer” initial mesh, the simulation has reduced the error to near 0%. The rtol study shows that the value of 1×10-4 is adequate for 2D axisymmetric and 1×10-5 for both 1D and 3D. Further investigations on complex electrochemistry using this platform are well justified and highly recommended. Given the reliability of COMSOL presented in the first study, the second study implement similar approach to model the experiment by Glandut et. al (2015) on Titanium carbide (TiC) support, tetrahedral amorphous carbon doped platinum (taC:Pt) electrode for hydrogen evolution reaction. The developed model was tested for surface diffusion in 2D and surface diffusion with edge effect in 3D. The simulation results show that kinetic parameters permutation with surface diffusivity shows some increased in current output but was unable to achieve the current output obtained from the experiment. However, the introduction of edge effect on the side of taC:Pt on TiC support would significantly increase the current output with great coherency to the experimental result. The edge exhibits kinetic properties unlike both TiC or taC:Pt. The kinetic parameters were determined using the simulation and a dataset was found to show great coherency with the experimental result. Surface diffusion was rendered negligible because negligible compared to the high kinetic parameters on the edge in comparison to the TiC and taC:Pt surface
Parametric study and CFD simulation of a heat-driven adsorber for an air-conditioning system employing activated carbon
Get PDFAdsorption cooling systems powered by waste heat or solar heat can help to reduce the use of ozone depletion substances, such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). In this research work, a CFD simulation works were conducted on a prototype adsorption air-conditioning system powered by waste heat that was successfully tested in laboratory. The aim is to measure the system performance of the adsorption cooling and verify the results with experimental works
Computational Studies of Confined Submerge Fan to Circulate and Oxygenate Hypolimnetic Layer in Hydro Power Reservoirs
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Kinetic study and simulation of molybdenum borides for hydrogen evolution reaction
Get PDFThis paper presented the kinetic study of molybdenum borides via the Volmer-Heyrovsky-Tafel (V-H-T) mechanistic steps for hydrogen evolution reaction (HER). A theoretical approach was carried out to investigate the kinetic properties of several molybdenum boride materials for HER in 0.5 M
H2SO4. Our findings offer definitive proof that the simulated results show that B, Mo, Mo2B, and α-MoB, proceed through V-H mechanistic steps (slower kinetics) while β-MoB and MoB2 exhibit V-H-T mechanistic steps with higher kinetics. The kinetic parameters were determined in terms of the standard rate constant parameters for the Volmer step (kV, k-V), Heyrovsky step (kH, k-H), and rate constant for the Tafel step (kT, k-T). The simulation was able to predict the overpotential at 10 mA/cm2, η10 recorded at
approximately 780, 585, 480, 350, 310, and 300 mV for B, Mo, Mo2B, αMoB, β-MoB, and MoB2 respectively. Based on these findings, the adopted mathematical model shows good coherency to the experimental findings.
The simulation work provides a good numerical estimation of the characteristics of the electrocatalyst for HER. This paper successfully elucidated the reaction mechanisms (V-H-T steps) and understood the ratelimiting steps involved in the HER process on Mo-B materials
The Sorption Studies of Waste Cooking Oil using Raw and Treated Pineapple Crown Leaf
Get PDFThe unregulated discharge of pollutants into water bodies has become an issue that led to pollution. Fiber derived from various forms of agricultural wastes as the sorbent is widely used as it has a high sorption capacity and efficiency. It is environmentally friendly and could be costeffective as it only utilizes the unwanted parts of plants, which usually would otherwise be discarded. The pineapple crown leaf (PCL) and other plants with high cellulose content have the potential for environmental applications. Oil pollutants, particularly waste cooking
oil (WCO) from the food and beverage industry, often contaminate water bodies due to poor waste management. Using cellulose-rich plants like PCL could offer an effective solution for absorbing these pollutants. This study examines the characteristics and sorption capacities of raw, NaOH-treatment PCL, and carbonized PCL to develop an effective, eco-friendly method for oil spill remediation. The
methodology involves washing, drying, grinding, and sieving PCL to obtain a powdered PCL. Then, raw PCL (RPCL) undergoes chemical treatment with 10% sodium hydroxide, NaOH and thermal treatment at 300 °C. The raw and treated PCL were characterized using Fourier Transform Infrared Spectroscopy (FTIR). The elimination of some noncellulosic components in NaOH-treatment PCL (CPCL) and carbonized PCL (TPCL) observed in the FTIR spectrum would contribute to higher sorption efficiency and capacity of WCO. In agreement with the results from FTIR analysis, the highest sorption efficiency in pure oil was shown by TPCL at 33% and CPCL in slick oil at 16.33%. The highest value for pure and slick oil recorded for sorption capacity was 9.23 g g −1 from TPCL samples and 4.3 g g −1 from CPCL samples. This study supports sustainable waste management and green technology for
environmental remediation, highlighting PCL's potential in mitigating oil pollution and the value of agricultural waste in creating eco-friendly solutions for oil disposal challenges
Kinetic Study and Simulation of Titanium Carbide-Supported, Platinum-Doped Tetrahedral Amorphous Carbon Electrodes for Hydrogen Evolution Reaction
No full textThis paper presents the kinetic study of titanium carbide (TiC)-supported, platinum-doped tetrahedral amorphous carbon (taC:Pt) referred to as TiC-taC, for the hydrogen evolution reaction (HER). This study employs the Volmer–Heyrovsky–Tafel (VHT) mechanism. A theoretical approach was utilized to investigate the kinetic properties of these materials for an HER in 0.5 M H2SO4. TiC-taC exhibited Volmer-dominated reactions with a Tafel slope of 40 mV/dec and the overpotential at 10 mA/cm2 was 185 mV. In contrast, isolated TiC and taC:Pt recorded significantly higher Tafel slopes with 60–110 mV/dec and overpotentials of 871 mV and 1009 mV, respectively. The developed model was tested in one dimension (1D) for individual TiC and taC:Pt. The simulated kinetics parameters were determined for both TiC and taC:Pt, revealing that TiC follows the VHT steps, while taC:Pt follows the VH steps. The simulation results show excellent coherence with the experimental results. Further simulation of the hybrid TiC-taC electrocatalyst was conducted considering surface diffusion and edge effects in two (2D) and three dimensions (3D). To the best of our knowledge, this FEM simulation approach is the first to be reported due to the unique geometry of the TiC-taC catalyst enabling the assumption of surface diffusion and edge effect. The introduction of edge effects on the taC:Pt side of the TiC support significantly enhanced the current output, aligning closely with experimental results. The edge exhibited distinct kinetic properties compared to both TiC and taC:Pt. The kinetic parameters determined from the simulation demonstrated strong agreement with experimental findings. Adding the edge effects was essential to explaining the higher current output from the TiC-taC electrode. It exhibited unique kinetic properties not observed in either TiC or taC:Pt alone, acting as a pump where it absorbs cHs from neighbouring sites due to surface diffusivity and releases H2 via the Heyrovsky reaction. While surface diffusion had a lesser effect, the simulation indicated its positive influence on the HER
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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