Impact of domain discretization on the accuracy of a 2D model of PCM module for ventilation application

Optimal selection of domain discretization for numerical Phase Change Material (PCM) models is useful to establish confidence in model predictions and minimize the time consumption for conducting design analysis. Very detailed and geometrically complex models are usually applied utilizing several million cells. A 2D numerical PCM model of a climate module for thermal comfort ventilation is investigated. The mesh independence was conducted on 22 different mesh sizes ranging from 70 to 10.870 nodes. Convergence criteria was evaluated based on average air supply temperature and total heat transfer between the PCM and the air within the simulation time interval. Less than 0.1 % change in the air supply temperature and the heat transfer between the PCM and the air was achieved with 5250 and 9870 nodes, respectively. Thereby highlighting that a relatively small amount of nodes can be considered to achieve sufficient accuracy to conduct analysis of PCM applications.

Numerical Evaluation of Cooling Technology for Preventing Thermal Runaway in Batteries

The growth of the energy market due to global eco-friendly policy issues is leading to the growth of the lithium-ion battery market related to the energy storage system (ESS). However, if a fire occurs in an ESS using lithium-ion batteries, it is difficult to penetrate fire extinguishing agents due to the structural characteristics of lithium-containing electrical fire and cell-unit batteries. For this reason, ESS needs to study fire prevention and diffusion prevention systems; in this paper, computational fluid dynamics (CFD) are utilized to evaluate the cooling properties of PCM and thermoelectric devices, which are easy to apply in practice. In the PCM model, the correlation between the mass of the PCM and its temperature rise time confirmed that temperature control through PCM is possible when the temperature of the heating battery is out of the normal range. In the thermoelectric module, the numerical results of the model with an output of 40 W under the input power of 200 W confirmed that the heating value and the output of the thermoelectric module can create thermal equilibrium in a short time.

Development of a Multi-Segment Parallel Compressor Model for a Boundary Layer Ingesting Fuselage Fan Stage

The present methodological study aims to assess boundary layer ingestion (BLI) as a promising method to improve propulsion efficiency. BLI utilizes the low momentum inflow of the wing or fuselage boundary layer for thrust generation in order to minimize the required propulsive power for a given amount of thrust for wing or fuselage-embedded engines. A multi-segment parallel compressor model (PCM) is developed to calculate the power saving from full annular BLI as occurring at a fuselage tail center-mounted aircraft engine, employing radially subdivided fan characteristics. Applying this methodology, adverse effects on the fan performance due to varying inlet distortions depending on flight operating point as well as upstream boundary layer suction can be taken into account. This marks one step onto a further segmented PCM model for general cases of BLI-induced inlet distortion and allows the evaluation of synergies between combined BLI and active laminar flow control as a drag reduction measure. This study, therefore, presents one further step towards lower fuel consumption and, hence, a lower environmental impact of future transport aircraft.

Revealing the Mutation Patterns of Drug-Resistant Reverse Transcriptase Variants of Human Immunodeficiency Virus through Proteochemometric Modeling

Drug-resistant cases of human immunodeficiency virus (HIV) nucleoside reverse transcriptase inhibitors (NRTI) are constantly accumulating due to the frequent mutations of the reverse transcriptase (RT). Predicting the potential drug resistance of HIV-1 NRTIs could provide instructions for the proper clinical use of available drugs. In this study, a novel proteochemometric (PCM) model was constructed to predict the drug resistance between six NRTIs against different variants of RT. Forty-seven dominant mutation sites were screened using the whole protein of HIV-1 RT. Thereafter, the physicochemical properties of the dominant mutation sites can be derived to generate the protein descriptors of RT. Furthermore, by combining the molecular descriptors of NRTIs, PCM modeling can be constructed to predict the inhibition ability between RT variants and NRTIs. The results indicated that our PCM model could achieve a mean AUC value of 0.946 and a mean accuracy of 0.873 on the external validation set. Finally, based on PCM modeling, the importance of features was calculated to reveal the dominant amino acid distribution and mutation patterns on RT, to reflect the characteristics of drug-resistant sequences.

Theoretical and Experimental Insights into the Tandem Mannich—Electrophilic Amination Reaction: Synthesis of Safirinium Dyes

Isoxazolo[3,4-b]pyridin-3(1H)-ones are ‘spring-loaded’ compounds that quantitatively react with iminium salts derived from formaldehyde and secondary amines to yield fluorescent Safirinium dyes. The mechanism and energetics of the above tandem Mannich–electrophilic amination reaction have been investigated experimentally and using theoretical methods. The hybrid B3LYP functional with GD3 empirical dispersion and range-separated hybrid functional ωB97XD, both combined with a PCM model, were applied to acquire the energetic profiles of the studied reaction with respect to the structure of secondary amine and isoxazolone used. Diastereoselectivity of the tandem reactions involving iminium salt derived from L-proline has been rationalized theoretically by means of density functional theory calculations.

Análise de RMS de 13C usando GIAO, CSGT e IGAIM: Fatores de escalonamentos de Terpenos

Terpenes are natural products that have several biological and pharmacological properties that are directly related to their chemical structures. In the structural determination of organic molecules, Nuclear Magnetic Resonance (NMR) is used on a large scale. The chemical shift (δ) being the most important parameter. The present study aims to develop and test (the elemol molecule will be used for this purpose) δ scaling factors from 13C to terpenes, based on linear regressions. 10 complex sesquiterpene molecules were selected with the unmistakably determined structures (confirmed with X-ray crystallography). The geometries were optimized at the B3LYP / 6-311 + G (d, p) level, in the gaseous phase, and the δ will be obtained at the PBE0 / aug-cc-pvdz level with three different approaches GIAO, CSGT and IGAIM, in phase gaseous and liquid, where the PCM model (polarized continum model) was used. The TMS (tetramethylsilane) was used as a reference and the experimental data of 13C were obtained in chloroform. The results of scaled RMS for the terpenes used to generate the scaling factors show that when the effects of the solvent are taken into account, even implicitly, there is an improvement in the reproduction of experimental data. However, the difference in scaled RMS values is not large enough to justify taking into account interactions with the solvent, at least with the PCM model. It is interesting to note that with the level of theory PBE0 / aug-cc-pvdz, the GIAO method presented a lower performance than the other 2 used. Another interesting point is that its calculation time, according to the simulations generated in this work, was, on average, 30% greater than the CSGT and IGAIM. Thus, for studies with terpenes, with this level of theory, the use of the GIAO method is not indicated.

A Prediction–Correction Solver for Real-Time Simulation of Free-Surface Flows in River Networks

A prediction–correction solver is presented here for rapid simulation of free-surface flows in dendritic and looped river networks. Rather than solving a large global algebraic system over the entire domain of river networks, the model solves subsystems for subdomains of branches in two steps: prediction and correction. With the help of the prediction–correction method (PCM), the partial linearization technique, the semi-implicit method, and the Eulerian–Lagrangian method (ELM), the model only needs to solve tridiagonal linear systems for branches and is free of any iteration. The new model was tested using a hypothetical looped river network with regular cross sections, the Three Gorges Reservoir (TGR) dendritic river network, and the Jing-south looped river system (with seasonally flooding branches). In the first test, a time-step sensitivity study was conducted and the model was revealed to produce accurate simulations at large time steps when the condition for application of the PCM to river networks was satisfied. In the TGR test, the PCM model provided almost the same histories of water levels and discharges as those simulated by the HEC-RAS model. In the Jing-south test, the mean absolute error in simulated water levels was 0.07–0.24 m, and the relative error in simulated cross-section water flux was 0.5–4.9% compared with field data; the conservation error was generally 2 × 10−4 to 3 × 10−4. The PCM model was revealed to be 2–4 times as fast as a reported model, which solves local nonlinear subsystems using two-layer iterations, and 1.2–1.4 times as fast as the HEC-RAS. Using a time step of 1200 s, it took the sequential code 26.8 and 23.1 s to complete a simulation of a one-year unsteady flow process, respectively, in the TGR river networks (with 588 cells) and the Jing-south river system (with 662 cells).

Geometry, tautomerism and non-covalent interactions of the drug halofuginone with the carbon-nanotube and γ-Fe2O3 nanoparticles: A DFT study

Halofuginone is a potential anti-malarial drug, which could exist as three possible tautomers. Herein, using density functional theory (DFT), and handling the solvent effects with the PCM model, the tautomerism of halofuginone was investigated. Intramolecular H-bonds play an important role in the stability of the tautomers. The conformer H1a is the most stable. Noncovalent interactions of the H1a conformer with the armchair (5,5) single-wall carbon nanotubes and ?-Fe2O3 nanoparticles were explored in several manners. The most stable form of them was determined. The intermolecular H-bonds play a substantial role in the energy behavior of the interaction between ?-Fe2O3 nanoparticles and halofuginone.