Semi-empirical Approach Research Articles

A novel semi-empirical approach to non-destructively evaluate the effect of infills on frame buildings

Masonry infilled frame (MIF) structures are commonly used as building system in many regions, and particularly in Latin American, Mediterranean, and Pacific countries, which are areas highly exposed to seismic events. It is well known that the influence of the infilled frames on the seismic response is affected by several sources of uncertainties which create unsafe unaccuracies in the seismic behaviour of a building. The use of existing complex models is an option which require a large number of specialized input values and data mostly obtained from in-situ destructive tests, thus making them infeasible in many practical cases. This research is a first attempt to provide an approach which provides prediction of the structural behaviour of a MIF with quantified uncertainty, and using as inputs values that can be obtained through a low-cost non-destructive test. The proposed method exploits the known interaction between the in-plane (IP) and out-of-plane (OoP) behaviour of the masonry wall by providing a semi-empirical model which predicts the IP stiffness of the MIF in terms of the measured OoP fundamental frequency. The semi-empirical approach has been nurtured with five experimental tests over one-fourth scale MIFs, where the OoP fundamental frequency variation has been obtained in terms of the IP deformation history. The results indicate that the proposed method can become a practical tool to experimentally quantify the contribution of the masonry infills of existing frame buildings, and also to theoretically predict it during design phase. However, a larger dataset of tests should be used on the calibration of the method before its application in real cases.

Simulation study of drag force characteristics of nanoparticles in transition regime

Transport properties of nanoparticles in gases have many practical applications, such as aerosol science, combustion, and micro- and nano-scale fabrication. A nanoparticle moving in a fluid is expected to experience a drag force, which determines the transport property of the particle. According to the Einstein relationship, the diffusion coefficient of a particle is inversely proportional to the drag force coefficient. However, in the transition regime, it is usually difficult to evaluate the drag force of suspended particles. A typical method is to extend the asymptotic solution of the free molecular or continuum limit to the transition regime. According to the gas kinetic theory, Li and Wang proposed a theoretical expression for drag force on nanoparticles in the free molecular regime, which is then extended to the entire range of Knudsen number following a semi-empirical approach [Li Z G, Wang H 2003 <i>Phys. Rev. E</i> <b>68</b> 061207]. For nanoparticles, it is necessary to verify the theoretical predictions since the gas-particle non-rigid-body interactions must be taken into account. In this work, the drag force on nanoparticle in the transition regime is investigated by using molecular dynamics (MD) simulation. To evaluate the drag force, a harmonic potential is used to the nanoparticle to constrain its Brownian motion in our MD simulation. In the steady state, the drag force can be obtained by the balance between the drag force and harmonic force. It is found that the gas-particle non-rigid-body interaction has a significant influence on the drag force of nanoparticle. For weak gas-solid coupling, the MD simulation results can be in good agreement with the prediction of Li-Wang theory. However, for strong coupling, there exists significant discrepancy between the MD simulation results and the theoretical results. Due to the gas-solid intermolecular interactions, gas molecules can be adsorbed on the nanoparticle surface, and after a time period, they may be re-emitted from the surface when they gain sufficient kinetic energy. Therefore, an adsorption-desorption equilibrium and an adsorption layer can be established on the particle surface. The adsorption layer enlarges the collision cross-sectional area and enhances the momentum transfer between gas molecules and the particle, and thus the drag force increases. This can explain the inconsistencies between the theoretical results and MD simulations. In this work, we introduce an adsorption ratio to evaluate the thickness of the adsorption layer. Then, the effective particle radius can be defined by the sum of particle radius and the thickness of the adsorption layer. By using the effective particle radius, the simulation values are in very good agreement with the theoretical predictions. The results of this work provide insights into the applications of nanoparticles in aerosol science.

Incorporating solvent effects in DFT: insights from cation exchange in faujasites.

Zeolites are versatile materials renowned for their extra-framework cation exchange capabilities, with applications spanning diverse fields, including nuclear waste treatment. While detailed experimental characterization offers valuable insight, density functional theory (DFT) proves particularly adept at investigating ion exchange in zeolites, owing to its atomic and electronic resolution. However, the prevalent occurrence of zeolitic ion exchange in aqueous environments poses a challenge to conventional DFT modeling, traditionally conducted in a vacuum. This study seeks to enhance zeolite modeling by systematically evaluating predictive differences across varying degrees of aqueous solvent inclusion. Specifically focusing on monovalent cation exchange in Na-X zeolites, we explore diverse modeling approaches. These range from simple dehydrated systems (representing bare reference states in vacuum) to more sophisticated models that incorporate aqueous solvent effects through explicit water molecules and/or a dielectric medium. Through comparative analysis of DFT and semi-empirical DFT approaches, along with their validation against experimental results, our findings underscore the necessity to concurrently consider explicit and implicit solvent effects for accurate prediction of zeolitic ionic exchange.

فاعلية برنامج تدريبي مقترح في تنمية مهارات البحث العلمي لدى معلمات العلوم الطبيعية وأثره على التفكير العلمي لدى طالبات المرحلة الثانوية بمحافظة الطائف التعليمية

The study aimed to find out the effectiveness of the proposed training program in the development of research skills among secondary school science teachers and the reflection of the impact of the program on the development of scientific thinking among their students in Taif. In order to achieve this goal, the researcher used a semi-empirical approach with experimental design, consisting of a single group and two tests (pre/post), the researcher has proposed the construction of the training program, a test of the research skills for science teachers and a measure of the scientific thinking of students. After verifying the veracity of the program and the validity and reliability of the test and measure, the study was applied to two samples: the first sample of secondary school science teachers and their number reached (45 teachers) in these three disciplines (Chemistry, Physics, and Biology). They were presented the proposed training program. Their pre and post performance was measured by a scientific research skills test. The second sample is second secondary and thread grade students, who have been taught by teachers who attended the training program and their number reached (204 students). Their pre and post performance was measured by a scientific thinking scale. The "T" test was used for both correlated and in dependent group, and Pearson correlation coefficient, ETA square, in order to test the hypotheses of the study. The study found a number of results, the most important were that the training program contributed in the development of the scientific research skills of science teachers of the secondary level, where significant differences have been found at the lowest level (α≤0.05) between the average performance of science teachers to the test of scientific research skills as a whole, and these differences were significant in favor of the post application. Also, the training program had an impact on the teachers, and this has been reflected in their students where it has been noticed an increase in the average performance of the students in the post test according to the measure of the scientific thinking skills after that their teachers passed the training program. In light of the results of the study, the researcher recommended several useful recommendations. It also provided a number of suggestions for future research studies that can be a complement to this study.

Adaptation of conical liquid sheet and spray morphologies to cross-flowing gas

A variety of industrial devices use liquid injection into the traverse stream of air. Ambient flow changes the spray characteristics, which can alter a system's function. Two different spill-return pressure-swirl atomizers (SRA) were investigated under cross-flow. One of the tested atomizers generates a conical liquid sheet with shorter breakup lengths due to reduced internal air-core stability. Phase Doppler anemometer (PDA) was used for 2D velocity and droplet size measurements, along with high-speed visualization to record instantaneous spray behaviour. A wide range of operating parameters was tested, e.g., inlet pressure (pl) ranging from 0.25 MPa to 1 MPa, spill-to-feed ratio (SFR) from 0 to 0.9, and cross-flow velocity from 0 to 32 m/s. As the cross-flow velocity increases, the spray starts to tilt and the breakup length (lb) shortens as a result of increased aerodynamic forces. This reduces the differences between atomizers. Moreover, the droplet diameter depends on the lb, yet no semi-empirical model was found to accurately predict the droplet sizes. A map of breakup modes was established, and a transition point from long- to short-wave mode was identified. The Linear Stability Analysis of the liquid sheet breakup was used and compared with a semi-empirical approach for the first time for the SRA and cross-flow conditions. The results imply that considering only quiescent ambient conditions during atomizer development might not lead to the optimal design.

Quantifying Volume Change in Porous Electrodes Via the Multi-Species, Multi-Reaction Model

Automotive manufacturers are working to improve individual cell and overall pack design by increasing their performance, durability, and range, while reducing cost; and active material volume change is one of the more complex aspects that needs to be considered during this process. As the time from initial design to manufacture of electric vehicles is decreased, design work that used to rely solely on testing needs to be supplemented or replaced by virtual methods. As electrochemical engineers drive battery and system design using model-based methods, the need for coupled electrochemical/mechanical models that take into account the active material change utilizing physics based or semi-empirical approaches is necessary[1-8]. In this study, we illustrated the applicability of a mechano-electrochemical coupled modeling method considering the multi-species, multi-reaction model as popularized by Verbrugge[9-14] and Baker. To do this, validation tests were conducted using a computer-controlled press apparatus that can control the press displacement and press force with precision. The coupled MSMR volume change model was developed and its applicability to graphite and NMC cells was illustrated. The increased accuracy of the model considering the coupled MSMR volume change approach shows in the importance of accounting for individual gallery volume change behavior on cell level predictions. References T. R. Garrick, K. Kanneganti, X. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014).T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, Ecs Transactions, 72, 11 (2016).T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017).T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017).D. J. Pereira, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 166, A1251 (2019).D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 167, 080515 (2020).T. R. Garrick, J. Gao, X. Yang and B. Koch, J. Electrochem. Soc. (2021).D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022).M. Verbrugge, D. Baker and X. Xiao, J Electrochem Soc, 163, A262 (2016).M. Verbrugge, D. Baker, B. Koch, X. Xiao and W. Gu, J Electrochem Soc, 164, E3243 (2017).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 165, A3952 (2018).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 167, 013504 (2019).D. R. Baker, M. W. Verbrugge and W. Gu, J Electrochem Soc, 166, A521 (2019).M. W. Verbrugge, X. Xiao and D. R. Baker, J Electrochem Soc, 167, 080523 (2020).

Unraveling the Interplay between Degradation Mechanisms during Battery Cycling Conditions: Influence on SEI Growth

Although the solid electrolyte interphase (SEI) is integral for the operation and stability of Li-ion batteries, its continuous growth over the battery life leads to in loss of cyclable material and overall degradation which results in capacity face. Therefore, a proper understanding of the mechanisms and factors involved in the SEI evolution during battery operation is integral for both reliable ageing models, allowing proper prognosis of the state of health (SoH), and improvement of battery lifetime.Generally, studies of SEI growth have focused on calendar ageing experiments, in which the battery is left undisturbed for long periods of time and periodic check-up cycles are performed to estimate the capacity loss over time. Despite significant advances in the understanding of SEI formation with this kind of experiments, the specific limiting mechanism for SEI growth is still under discussion, with electron or Li-interstitial diffusion through the SEI being the main candidates in recent studies. Calendar ageing provides a suitable framework to study SEI growth in almost isolation from other degradation mechanisms but neglects the synergistic effects that can occur between them in real operation conditions, in which the SEI growth will be influenced by other degradation processes. For example, it has been reported that lithium plating can favor SEI formation and that new SEI will growth in exposed active material through cracks in the particles or in the existing SEI. Although initial efforts towards accounting for these synergies are already present in the literature, they have been applied to sparse sets of data and particularized for single chemistries.In this work we focus on the study SEI growth during cell operation and its interplay with other degradation mechanisms in the cell in different regimes to partially isolate degradation processes (e.g., varying cut-off voltages to favor lithium plating). To this end, we carry out electrochemical cycling tests with LNO/Gr and NMC811/Gr full coin cells and also assemble 3-electrode cells to differentiate between positive and negative electrode contributions. Moreover, the individual contributions from the different degradation mechanisms are assessed by combining EIS measurements, incremental capacity analysis and morphological characterization.The results of the characterization are then used to parametrize the implementation of degradation models (SEI, particle cracking, lithium plating, loss of active material...), with both semi-empirical and physics-based approaches, within a Doyle-Fuller-Newman pseudo-2D framework. The results of the model are then compared with the full coin cells experiments and used to evaluate the degradation synergies and provide best-practice approaches to balance battery performance and lifetime. Moreover, the flexibility of the model with degradation is tested using larger publicly available and literature datasets for different chemistries to assess its suitability in cases for which the complete model parameterization is not available (as it is often the case in commercial cells).

Semi-empirical approach to assess externally-induced photoluminescence linewidth broadening of halide perovskite nanocrystals with particle-size distribution

Colloidal nanocrystals (NCs) can be used to prepare high-color-purity metal halide perovskites (MHPs) for light-emitting displays. However, the NCs have a finite particle-size distribution, which broadens the linewidth of photoluminescence spectra under strong quantum confinement, and thereby degrades the color purity of the MHPs. This paper presents a simple method to quantify this externally-introduced broadening of linewidth ΓSD\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{{\\boldsymbol{\\Gamma }}}}}}}_{{{{{{\\bf{SD}}}}}}}$$\\end{document} by combining experimental size-distribution histogram with size-dependent photoluminescence-wavelength (PL-λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{\\boldsymbol{\\lambda }}}}}}$$\\end{document}) curve. We develop a semi-empirical method to estimate the other three contributions to the experimentally-measured full-width at half-maximum, ΓEXP\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{{\\boldsymbol{\\Gamma }}}}}}}_{{{{{{\\bf{EXP}}}}}}}$$\\end{document}. Namely: the intrinsic linewidth ΓLO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{{\\boldsymbol{\\Gamma }}}}}}}_{{{{{{\\bf{LO}}}}}}}$$\\end{document} caused by exciton-longitudinal optical (LO) phonon Fröhlich coupling; the inhomogeneous linewidth Γo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{{\\boldsymbol{\\Gamma }}}}}}}_{{{{{{\\bf{o}}}}}}}$$\\end{document} caused by imperfections-related scattering, and the broadening ΓQC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{{\\boldsymbol{\\Gamma }}}}}}}_{{{{{{\\bf{QC}}}}}}}$$\\end{document} due to the quantum-confinement effect. We show that ΓLO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{{\\boldsymbol{\\Gamma }}}}}}}_{{{{{{\\bf{LO}}}}}}}$$\\end{document} of a nanocrystal decreases together with the particle size, disappearing at 1.6 nm radius. Finally, we show that ΓLO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{{{{\\boldsymbol{\\Gamma }}}}}}}_{{{{{{\\bf{LO}}}}}}}$$\\end{document} is correlated with the degree of Fröhlich-polaron formation, hence proportional to the long-range LO-phonon-electron coupling.

A binary medium model of frozen soil-structure interface considering the roughness effect

The constitutive model of the frozen soil-structure interface is a critical component of frozen soil mechanics research, and the surface roughness plays a significant role in determining the interaction between the soil and structure. Most of the previous research about the interface roughness mechanical behavior is based on numerical simulations, and these methods mainly depend on empirical and semi-empirical approaches to determine parameters. However, there is a lack of sufficient research on the internal mechanisms of micro-mechanical deformation of the contact surface based on roughness. To elucidate the impact of roughness on the deformation mechanism and mechanical behavior of frozen soil, a series of cryogenic direct shear tests and a binary medium model based on the interface of frozen soil-structure were conducted. The test was carried out at −4 °C under different normal load and roughness conditions. The test results showed that the shear curve of the specimen interface presented brittle failure, and the stress peak was evident at this temperature. Moreover, the shear zone was introduced to explain the change of roughness on the mechanical behavior of the samples. A binary medium constitutive model was established to depict the overall mechanical behavior of the interface during prepeak shear with different roughness. The simulated roughness, displacement, and shear stress are in good agreement with the measured data. The effectiveness of the model is evaluated by correlated factors, and it is verified that the model can properly depict the change of roughness on the mechanical characteristics of the interface.

Semi-empirical growth model of InSbBi grown by molecular beam epitaxy

The molecular beam epitaxy growth of bump-free indium antimonide-bismide (InSbBi) necessitates precise control of group III and V stoichiometry, as well as the growth temperature and rate. In this research, we propose a semi-empirical growth model approach to enhance our understanding of the involved growth kinetics and predict the bismuth (Bi) content and surface quality of InSbBi films. The model combines the impact of growth rate and the maximum incorporation rate of Bi on the Bi content of InSbBi. Our findings indicate that bump-free InSbBi requires a minimum Bi incorporation rate to Bi adatoms arrival rate (or Bi flux) ratio of 0.96, which closely approaches the ideal value of 1.0. By employing this growth model, we can optimize the growth conditions for achieving high-quality InSbBi films with controlled Bi content.

Electron-induced ionization cross-sections for C5H5N

The secondary electron energy-dependent partial differential ionization cross sections at fixed incident electron energies 100 and 200 eV and their integral or total ionization cross sections in the incident electron energy range ionization threshold to 5 keV for C5H5N Bio-molecule due to electron impact corresponding to the produced major cations are calculated by employing revisited Jain-Khare semiempirical approach. The averaged secondary electron energy and the ionization rate coefficients are calculated from the ionization threshold to 5 keV. The present results are compared with available experimental and theoretical results and are found to be in satisfactory agreement.

PREDICTION OF DRAG AERODYNAMIC COEFFICIENT OF THE 155MM PROJECTILE UNDER AXISYMMETRIC FLOW USING DIFFERENT APPROACHES

The determination of the total aerodynamic load which negatively influences the movement of artillery projectiles is inevitable and indispensable in order to be able to increase or control their ranges. The main part of this aerodynamic load that has the most influence on projectile movement is the drag force, which acts in the opposite direction to the velocity vector and therefore opposes its movement. From this, in this present work, the total drag coefficient of the 155mm M107 axisymmetric projectile under axisymmetric flow, at zero yaw, was predicted by semi-empirical and computational fluid dynamics (CFD) approaches in the three flow regimes, also the influence of its components on the total drag was analysed. The average deviation of the total drag coefficient in the three flow regimes, compared to the reference experimental results, is 5.7% for the semi-empirical results and 1.7% for the computational results. Analysis of the influence of the total drag components, such as pressure drag, friction drag and base drag, permitted to calculate their influence rates on the total drag as a function of Mach number and flow regime.

A kinetic study on oxygen redox reaction of a double-perovskite reversible oxygen electrode— Part II: Modelling analysis

Mixed ionic and electronic conductor double perovskites are very promising oxygen electrode materials for solid oxide cell technology. However, understanding their specific kinetic mechanism is a fundamental preliminary step towards detecting the best reachable performance, optimising the operation conditions and the electrode architecture. Indeed, the contributions of different rate-determining steps can vary as a function of the working point. In this framework, after a detailed experimental campaign devoted to the study of SmBa0.8Ca0.2Co2O5+δ (SBCCO) oxygen electrode behaviour, the authors propose a theoretical analysis of oxygen reduction and oxygen evolution reaction paths that couples a preliminary study through equivalent circuit analysis with a physics-based model to predict the operation of SBCCO as a reversible oxygen electrode. Following a semi-empirical approach, the kinetics formulation was derived from thermodynamics and electrochemistry fundamental principles and was tuned on electrochemical impedance spectroscopy (EIS) spectra in order to retrieve the unknown kinetic parameters. The successful cross-checking of the simulated results with the experimental data obtained by direct current measurements validated the proposed model, here applicable in further works on full cells to simulate the SBCCO oxygen reversible electrode performance.

Investigation of the structural, mechanical, radiation and neutron shielding properties of the TeO2-B2O3-Li2O-MoO3-CuO glass system

In this study, the structural, mechanical, radiation and neutron shielding properties of (78-x)(0.4TeO2-0.6B2O3)− 20Li2O-xMoO3-2CuO glass system, were investigated. A variety of characterisation methods, including optical absorption spectroscopy, FTIR, EPR, and X-ray diffraction, were used to examine the structural characteristics. Molecular orbital coefficients were calculated from EPR and optical absorption measurements. EPR lines of both Cu2+ and Mo5+ ions were observed in the EPR spectra. The mechanical properties were assessed through experimental measurements, while the elastic properties were evaluated using the semi-empirical approaches of the Makishima and Mackenzie model, along with the bond compression model. The inclusion of 4% MoO3 led to noteworthy enhancements in both hardness and fracture toughness. Hardness increased from 4.364 to 4.664 GPa, and fracture toughness improved from 0.980 to 1.226 MPa.m1/2. The mass attenuation coefficients (MAC), mean free paths (MFP), half-value layers (HVL), and effective atomic numbers (Zeff) were measured in the energy range of 59.54–661.62 keV. The measurement of equivalent dose rates resulting from the absorption of fast neutrons was conducted utilizing a 241Am-Be fast neutron source with an activity of 10 mCi. The exposure buildup factor (EBF) and the fast neutron removal cross section (ΣR) were therotically calculated. The potential suitability of glasses for nuclear security applications was assessed by evaluating their proton and alpha shielding properties. The study found that glasses containing higher amounts of TeO2 and MoO3, within the TeO2-B2O3-Li2O-MoO3-CuO composition, demonstrated enhanced capabilities for shielding against radiation and neutrons.

Aircraft noise impact prediction with incorporation of meteorological effects

As part of a research effort towards greener aviation, this study focuses on the noise impact of aircraft operations around major airports. First, a pre-existing aircraft noise prediction platform based on a simplified (semi-empirical) approach is refined, to account for all refraction effects inherited from realistic (e.g., heterogeneous) atmospheres. To do so, the platform is enhanced with a more advanced noise propagation kernel relying on Ray Tracing, which combines state-of-the-art functionalities and novel refinements (e.g., to account for the three-dimensional nature of winds). This improved prediction platform is then validated against various benchmark cases, delivering outcomes of both phenomenological and methodological natures (e.g., the importance of accounting for 3D wind patterns whilst numerically handling them with care). Finally, the platform is applied to real-life situations involving representative aircraft operations and actual meteorological conditions, revealing how weather variations can significantly alter the propagation − and thus impact − of aircraft noise.

Application of composite material models to determine the Young’s modulus of the grid pattern of partially infilled 3D printed samples

Abstract Additive manufacturing makes it possible to fabricate samples with partial internal infill. This type of sample has a different Young’s modulus than a completely filled sample. In this work, the dependence of the apparent Young’s modulus of samples manufactured by 3D printing on the infill percentage has been experimentally determined, for a given pattern and using a non-destructive technique. Young’s modulus was assumed as an apparent modulus and values were found between 3.39 GPa for the sample with 100% infill and 1.32 GPa for the sample with 20% infill. In particular, a non-linear variation of the apparent Young’s modulus was observed. The specific Young’s modulus presents a minimum for an intermediate infill percentage. The use of a model of composite materials was proposed, as a first approach to determine the apparent Young’s modulus of the parts. The mixture law, the Halpin-Tsai equation generalized by Kerner, a model of foams and the Mori Tanaka method were applied to the dependence of the apparent Young’s modulus on the infill percentage, giving all, except the mixture law, acceptable results. The advantage of applying each model was discussed. This type of analysis would allow a fast semi-empirical approach of the apparent Young’s modulus in partially filled samples with a grid pattern.

Graphene/gadolinium oxide composite modified screen-printed electrochemical sensor for detection of diclofenac sodium

This study investigates the electrochemical sensing of diclofenac sodium. A bare single screen-printed carbon electrode was modified with graphene/gadolinium (III) oxide (Gd2O3) where graphene serves as the conductive support material for the electrode. The interaction between the elements of graphene/Gd2O3 composite and diclofenac with graphene/Gd2O3 composite has been studied by density functional theory (DFT). The characterization of the nanocomposite underwent through some sophisticated characterization techniques like field-emission scanning electron microscopy (FE-SEM), Energy Dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD). Electrochemical techniques like cyclic voltammetry (CV) were used for studying the chemical kinetics and absorbance of the nanocomposite while Differential Pulse Voltammetry (DPV) was used to study the oxidation of Diclofenac. The electrochemical studies exhibit a linear range of detection from 5.89 µM to 66.7 µM concentration of the analyte. Importantly, in-silico studies based on the semi-empirical (PM6) approach strongly favoured the experimental outcomes especially, the binding features involved the both the dimer complex versus the trimer complex. The binding energy of the three components-based model (Graphene-Gd2O3-Diclofenac) has been calculated to be extremely larger than that of the two components-based model (Graphene-Diclofenac). This novel Diclofenac biosensor showed satisfactory results and it has the potential to create a great platform in the environmental monitoring system.

Storage and Diffusion of Carbon Dioxide in the Metal Organic Framework MOF-5─A Semi-empirical Molecular Dynamics Study.

Metal-organic frameworks (MOFs) have attracted increasing attention due to their high porosity for exceptional gas storage applications. MOF-5 belongs to the family of isoreticular MOFs (IRMOFs) and consists of Zn4O6+ clusters linked by 1,4-benzenedicarboxylate. Due to the large number of atoms in the unit cell, molecular dynamics simulation based on density functional theory has proved to be too demanding, while force field models are often inadequate to model complex host-guest interactions. To overcome this limitation, an alternative semi-empirical approach using a set of approximations and extensive parametrization of interactions called density functional tight binding (DFTB) was applied in this work to study CO2 in the MOF-5 host. Calculations of pristine MOF-5 yield very good agreement with experimental data in terms of X-ray diffraction patterns as well as mechanical properties, such as the negative thermal expansion coefficient and the bulk modulus. In addition, different loadings of CO2 were introduced, and the associated self-diffusion coefficients and activation energies were investigated. The results show very good agreement with those of other experimental and theoretical investigations. This study provides detailed insights into the capability of semi-empirical DFTB-based molecular dynamics simulations of these challenging guest@host systems. Based on the comparison of the guest-guest pair distributions observed inside the MOF host and the corresponding gas-phase reference, a liquid-like structure of CO2 can be deduced upon storage in the host material.

Charge carrier dynamics in conducting polymer PEDOT using abinitio molecular dynamics simulations.

As conducting polymers become increasingly important in electronic devices, understanding their charge transport is essential for material and device development. Various semi-empirical approaches have been used to describe temporal charge carrier dynamics in these materials, but there have yet to be any theoretical approaches utilizing abinitio molecular dynamics. In this work, we develop a computational technique based on abinitio Car-Parrinello molecular dynamics to trace charge carrier temporal motion in archetypical conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). Particularly, we analyze charge dynamics in a single PEDOT chain and in two coupled chains with different degrees of coupling and study the effect of temperature. In our model we first initiate a positively charged polaron (compensated by a negative counterion) at one end of the chain, and subsequently displace the counterion to the other end of the chain and trace polaron dynamics in the system by monitoring bond length alternation in the PEDOT backbone and charge density distribution. We find that at low temperature (T = 1K) the polaron distortion gradually disappears from its initial location and reappears near the new position of the counterion. At the room temperature (T = 300K), we find that the distortions induced by polaron, and atomic vibrations are of the same magnitude, which makes tracking the polaron distortion challenging because it is hidden behind the temperature-induced vibrations. The novel approach developed in this work can be used to study polaron mobility along and between the chains, investigate charge transport in highly doped polymers, and explore other flexible polymers, including n-doped ones.

Development of a semi empirical calculation approach for the determination of percentage depth dose in water for higher energy photon beams using a medical linear accelerator

The development of a calculation approach to determine the Percentage Depth Dose (PDD) by manual calculation for medical linear accelerator of 6 MV and 15 MV photon beam energy. The equation to determine PDD can be divided into two components i.e., the primary component and the scatter component. To calculate the primary component, the linear attenuation coefficient needs to be calculated. The measurement of charge was taken at various depths and for different field sizes using 6 MV and 15 MV photon beams. To determine the linear attenuation coefficient, a graph of ln (MR) where, MR represents corrected meter reading was plotted against depth in cm. By plotting another graph of linear attenuation coefficient against field size, to determine the effective linear attenuation coefficient. The scattered component KS was graphically plotted against depth in cm and derived an equation for scatter component. The calculated PDD for 6 MV was found to be within 1 % difference and for 15 MV percentage difference within 3 %. It was found that numerically developed PDD values table for higher energy photon beam becomes valid and it can be utilized for the manual dose calculation.