Scientific Research Discussions

This study examines the desorption of formic acid molecules and methane molecules on the surface of MoS2 based on density functional theory. There are two alternative desorption trajectories of formic acid and methane molecules. The first alternative is to release the methane molecules first from the surface and then continue with the release of formic acid molecules. The second alternative is to release the formic acid molecules first from the surface and then continue with the release of methane molecules. The desorption energy in both alternatives is varied with the density of hydrogen atoms of 0%, 33.3%, 66.7%. The results show that through both alternatives the desorption energy produced is the same. The desorption energy for hydrogen densities of 0%, 33.3%, and 66.7% is 2.44 eV, 2.99 eV, and 2.44 eV, respectively.

We have shown the isomerization reaction is one of the phenomena of quantum tunneling in the molecular level. We investigated the Trans-HCOH to H2CO isomerization reaction as the example. This project is focused on three fundamental questions : (a) How the reaction mechanism of Trans-HCOH to H2CO?, (b) How the Water Molecules (H2O) can catalyze the Trans-HCOH to H2CO reaction?, and (c) Which is the most preferable catalyze scheme for Trans-HCOH to H2CO?. To answer these questions, we employ the DFT calculation to predict the reaction pathways for each scheme, and then we calculate the chemical reaction rate via Tunneling Probability from Wentzel-Kramers-Brillouin (WKB) Approximation in Quantum Mechanics.  We are trying to confirm the mechanism that is shown in "Theoretical Investigation of the isomerization of trans-HCOH to H2CO: An example of a water-catalyzed reaction" by Peters et.al in the Journal of Physical Chemistry A".

In this study, geometric and electronic structure calculations have been carried out for PbTiO3 and BaTiO3 perovskite materials with Density Functional Theory (DFT) studies. This research is reviewed at room temperature for the bulk system and tetragonal phase. Electronic structure calculations show the presence of spin splitting in the tetragonal structure caused by the breakdown of symmetry inversion. The resulting spin splitting is an effect caused by the ferroelectric properties of the material that can increase the ability to read data faster and more efficiently. The resulting spin splitting is Rashba type for PbTiO3 material located at point X and BaTiO3 at point Gamma, with parameters obtained by energy fitting calculation using point group symmetry C4v. By using the optimized tetragonal lattice of 3.972 Angstrom; 4.233 Angstrom and 4.076 Angstrom; 4.094 Angstrom Pb and Ba respectively, it is known that there is a change in the band structure energy in the material given the effect of strain (-8%, -6%, -4%, -2%, +2%, +4%, +6%, +8%). In the PbTiO3 system, the largest band structure when given the minimum strain effect (-8%) of 1.73 eV and the trend of the band structure graph tends to decrease inversely proportional to the strain effect. In the BaTiO3 system, the band structure has an increasing trend as the number of strains increases. The largest band structure at a strain (+6%) of 1.76 eV, because the bandgap value at a strain of -8% BaTiO3 system is anomalous to other band structures with strains (-6% ... 8%). In here, the QML only assists the theoretical calculation that involving Rashba and Dresselhauss Effect + DFT Principles

As a heat exchanger, it is expected to have high effectiveness. This final project focuses on research on the comparison of the characteristics of one and two-pass Intercoolers with dome variations. Intercoolers with one-pass types have effectiveness, heat transfer rate and pressure drop of 72.215%, 2832.064 W, and 2214.988 Pa, respectively. While the two-pass intercooler with the first variation has an effectiveness of 86.950%, a heat transfer rate of 3449.295 W, and a pressure drop of 5023.982 Pa, for the two-pass second variation, it has an effectiveness of 86.843%, a heat transfer rate of 3445.201 W, and a pressure drop of 1840.063 Pa and for the two-pass three variations, it has an effectiveness of 86.843%, a heat transfer rate of 3446.216 W, and a pressure drop of 1700.922 Pa. Based on this research, a two-pass intercooler with three variations is more optimal because the pressure drop is smaller compared to other variations but the heat transfer is higher than a single pass. 

In this research, thermal analysis are done by combining several methods: (a) Senjaya's Model of the Intercooler's Tube Thermal Resistance, (b) Fins Convection model by Incropera, and (c) LMTD (Logarithmic Mean Temperature Difference). We justify the results by applying the Computational Fluid Dynamics (CFD) via FLUENT 6.3 ANYSIS.