Initial Geometry Research Articles

Machine learning-accelerated aerodynamic inverse design

The computational cost of iterative design methods has been a challenge in aerodynamics. In this research, the data-driven acceleration of an iterative inverse design method was implemented to reduce its computational cost. Although iterative design methods are robust, a lot of unwanted data is generated during their intermediate stages. Inverse design methods rely on correcting an initial geometry based on a given target parameter distribution. The generated data during the early iterations of the inverse design was incorporated into two deep-learning models to accelerate target geometry attainment. The deep learning models were used to recognize the correlation between the pressure distribution and corresponding geometry as well as the meaningful changes of geometry and pressure distribution toward their targets. The deep learning models were validated in viscous and inviscid compressible flows for various benchmark aerodynamics problems. In conclusion, between 70 to 80% computational cost decrease was observed for online uses of the machine learning module with the inverse design algorithm. This approach suggests incorporating machine learning techniques into design algorithms by exploiting the intermediate data for further improvement of them. We draw a new interpretation of learning dynamic changes through consecutive iterations instead of typical time-dependent problems in the use of LSTM network.

A zero energy-input nitrogen removal reactor based on a short-circuited microfluidic fuel cell.

Excessive discharge of ammonia nitrogen would deteriorate water quality. In this work, we designed an innovative microfluidic electrochemical nitrogen-removal reactor (MENR) based on a short-circuited ammonia-air microfluidic fuel cell (MFC). The MENR utilizes the laminar characteristics of two flows (an anolyte containing nitrogen-rich wastewater and a catholyte of acid electrolyte solution) in a microchannel to establish an efficient reactor system. At anode, ammonia was catalyzed by a NiCu/C modified electrode to N2, while O2 in the air was reduced at cathode. In essence, the MENR reactor is a short-circuited MFC. Maximum discharge currents were achieved accompanied with strong ammonia oxidation reaction. Factors indicating electrolyte flow rate, initial nitrogen concentration, electrolyte concentration, and electrode geometry have various effects on the nitrogen removal performance of the MENR. Results indicate that the MENR showed efficient nitrogen removal properties. This work proposes an energy-saving process by using the MENR to remove nitrogen from ammonia-rich wastewater.

Transverse momentum decorrelation of the flow vector in Pb–Pb collisions at sqrt{s_{_{textrm{NN}}}} = 5.02 TeV

Anisotropic flow, typically defined as the azimuthal correlations of the produced particles with respect to the common symmetry plane over a large kinematic, has been a popular approach in the last three decades to explore the properties of hot and dense QCD matter in high-energy heavy-ion collisions. These flow studies are usually based on the multi-particle correlations method, assuming that multi-particle correlations can be factorized into the product of flow coefficients. However, recent LHC measurements, based on new four-particle correlation observables, show evidence of flow angle decorrelation and flow magnitude decorrelation. These decorrelations break the assumption of the common symmetry plane and factorization. In this paper, we perform systematic studies to investigate the decorrelation with A Multi-Phase Transport (AMPT) model. We examine different tunings of the initial conditions, partonic cross sections, and hadronic interactions, revealing that the decorrelations are mainly driven by the initial geometry fluctuations while weakly influenced by the system’s dynamic evolution. Comparison to experimental data and the AMPT calculations presented in this paper promotes a new possibility to further constraints on the initial conditions of the heavy-ion collisions.

Initial shape reconstruction of a volcanic island as a tool for quantifying long-term coastal erosion: the case of Corvo Island (Azores)

Abstract. Long-term coastal erosion is not yet well studied given that it is difficult to quantify. The quantification of long-term coastal erosion requires reconstruction of the coast's initial geometry and the determination of where and when the erosion started. Volcanic islands fulfill these two conditions: their initial shape is roughly conical and the age of the lavas that generated this geometry is easily measured. We have developed a method to reconstruct the initial shape of simple volcanic edifices from aerial and submarine topographic data. The reconstructed initial shape and associated uncertainties allow us to spatially quantify the coastal erosion since the building of the island. This method is applied to Corvo Island in the Azores archipelago. We calculated that, due to coastal erosion, the island has lost a volume of 6.5 ± 2.7 km3 and roughly 80 % of its surface area since it first came into being. Taking the large uncertainty in the age of the topmost lava flows (0.43 ± 0.34 Myr) into account, we have estimated that Corvo Island has lost an average of 5000 to 100 000 m3 yr−1 of its volume due to coastal erosion. Lastly, we show a strong correlation between long-term coastal erosion and the spatial distribution of the waves. Specifically, we highlight a stronger control on erosion by smaller and more frequent waves than by storm waves. The next step will be to apply this method to other volcanic islands in order to (i) streamline and improve the method and (ii) verify the correlations observed in the present study.

Thermally-induced shape memory behavior of polylactic acid/polycaprolactone blends

A study of the shape memory effect on extruded polylactic acid (PLA) and polycaprolactone (PCL) blends, which were transformed into films and movable components of articulated specimens by hot pressing and 3D printing, respectively, is presented. After characterizing their chemical structure by FTIR spectroscopy and their wettability, the thermal properties and mechanical response of the blends were evaluated and compared with those of neat PLA and PCL. The blends exhibited very good interfacial adhesion between the phases, even though they are immiscible polymers. The thermoresponsive shape memory effects of neat PLA, neat PCL and PLA/PCL blends with different compositions (90/30, 70/30 and 50/50 w/w%) were evaluated considering three consecutive heating–cooling cycles. Comparison of the initial permanent state geometry with the geometries achieved after each heating–cooling cycle for both films and 3D printed specimens, evidenced that the 70/30 w/w% blend exhibited the best behavior. Thus, the blends obtained with such composition showed the maximum reversibility between the temporary and permanent states (i.e. highest shape recovery capability) and shape fixing of such two states.

Effect of initial failure geometry on the progress of a retrogressive seepage-induced landslide

Natural and man-made slopes can undergo a retrogressive landslide when subjected to seepage. Studying the mechanism of retrogressive landslides contributes greatly to the employment of effective mitigation approaches. A multi-stage limit equilibrium-based study was performed to explore how the geometry of initial failure affects the progress of a retrogressive, multiple-rotational landslide caused by seepage flow. Seepage-stability analyses were carried out on two silty sand slopes which were previously found to experience successive rotational failures upon raising the water table in centrifuge tests. Analyzed in prototype dimensions were the slope models with the height of 24 cm and inclinations of 45° (1V:1H) and 63.4° (2V:1H) tested at different centrifugal accelerations. According to the tests, the initial shallow failures were assumed to be circular initiating from the face and emerging from the toe of the slopes in the stability analyses. The impact of curvature and length of the initial failure surface (referred to as IFS) as well as the height of the scarp shaped at each failure episode were investigated. The results show that the landslide continues until the slope profile finds a stable curvature. For the landslides that occur in the 45° inclined slope, when the initial failure initiates at a higher elevation on the slope face, the landslide retrogresses further. In addition, with an increase in the length or curvature of IFS, the final retrogression distance decreases. Further, it was observed that the progress of landslides depends on the height of the scarp exposed at each failure episode.

Simulative Investigation of Optimal Multiparameterized Cooling Plate Topologies for Different Battery System Configurations

To design an effective battery thermal management system, multiple simulations with different levels of modeling, physics, and details are generally needed. However, complex and high‐resolution models are time‐consuming, both in terms of buildup and in computation time. Especially the fast‐moving early‐stage development phases demand all‐in‐one model approaches allowing for quick and efficient concept evaluations. To meet these requirements, herein, a lumped‐mass modeling approach is proposed and a methodology for evaluating various liquid cooling plate topologies is derived. The framework aims to assist the volatile concept phase of battery system development in providing multidimensionally optimized cooling plate topologies. A novel modeling strategy preselects plate parameters using a reduction procedure that couples the transient models’ accuracy with the steady‐state models’ computation time advantages. The results analyze different initial battery geometries, indicating significant deviations in their optimized cooling plate properties. Plate topologies are varied between their main construction design parameters: tube size and tube‐to‐tube distance. In addition to battery's mean temperature, further meaningful parameters like resulting volume flow are evaluated, compared, and discussed for the entire set of battery geometries. Subsequent sensitivity analyses show geometry‐related optimal plate topologies depending on the cooling circuit performance, stressing the necessity for early‐stage cooling plate investigations.

Structural, Elastic and Mechanical Properties of Cubic Perovskite Materials

In this manuscript, theoretical work has been done on series of cubic perovskites RbVF3, RbMnF3, RbFeF3, RbCoF3, RbNiF3, RbCuF3, and RbZnF3. The main focus is on to compute structural, elastic and mechanical properties of cubic materials. All subjected computational results are collected by using Linearized Augmented Plane Wave (FP-LAPW) method using Density Function Theory (DFT). The calculated structural parameters including initial geometry optimization, energy minimization calculations, and total energy values reasonably agree with the previous work. The elastic properties contain C11 (for length), C12 (for volume) and C44 (for shape). These constants are used for calculations of different parameters to discuss mechanical properties. The results show that series of RbMF3 (V, Mn, Fe, Co, Ni, Cu and Zn) contains metallic bonding and anisotropic behavior. The temperature increases from RbVF3 to RbZnF3.These materials are ductile by nature. However, among all materials, RbZnF3 is the hardest material and also contains highest melting temperature. Hence by calculating these useful elasto-mechanical results they can be applicable in various devices for technological benefits so the current investigation signifies that these calculations provide a baseline for new researchers to establish further work.

Theoretical process for the investigation of dielectric characteristics of F3NO as an alternative gas for SF6

To examine the possibility of using a gas molecule as an SF6 alternative gas, the insulation properties of the molecule must be estimated. In this work, we present a theoretical approach to calculate geometry parameters, electron scattering cross sections, and transport properties of nitrogen fluoride oxide (F3NO), which we have selected as an alternative to SF6. The molecular minimum structure of F3NO was optimized using the ɷB97X-D functional combined with the aug-cc-pVTZ basis set. Using this initial geometry obtained by the molecular structure calculation, the R-matrix calculation was done to obtain the elastic and momentum transfer cross section. The BE-f method was used for electronic excitation cross section. For the ionization cross section, the binary encounter Bethe method was used. From the calculated cross section data, the electron transport coefficients and reaction coefficients were calculated by solving the two-term approximated Boltzmann equation to investigate the discharge and insulation characteristics.

A Review on Biomechanics and Development of Finite Element Models of Human Head Neck System

Abstract: The biomechanics of human head neck system could be better understood by creating finite element models of the same that accurately represents most of the components of head and neck. The initial geometry of the human head and neck was obtained using the computer tomography scans. The finite element models are created from these computed tomography scans and are further undergone through the various analysis procedures of finite element analysis. Thus, the developed finite element head neck models could be studied for various kinds of impacts acting on the head neck system during the time of any vehicle collisions, spaceflights etc. The development of these models and the various impact studies helps in the safety of the people. In this paper the concept of Finite element method, application of finite element method in biomechanics and various steps involved in this method are discussed in detail. Similarly, the finite element models of head and neck system developed by various researchers are also considered.

Star-forming environments in smoothed particle magnetohydrodynamics simulations I: clump extraction and properties

ABSTRACT What is the nature of a star-forming clump? Observations reveal these to be chaotic environments being modified and influenced by many physical processes. However, numerical simulations often define these initial star-forming clumps to be idealized objects. In this paper, we define and analyse 109 star-forming clumps extracted from our previous low-mass star cluster simulations. To define a clump, we identify all the gas in a simulation that ever becomes bound to or accreted onto a star, then follow the gas backwards in time until it decreases to a critical density. This gas and its neighbouring gas are defined as our star-forming clump. Our clumps span a mass range of 0.15 ≲ M/M⊙ ≲ 10.2, while the density range within each clump spans 2–4 orders of magnitude. The gas density distribution is not smooth, indicating that it is highly structured. The clumps are turbulent, with no coherent rotation. Independent of the initial magnetic field strength of the parent cloud, all clumps yield a similar range of field strengths. The clump magnetic field is ordered but not reflective of the initial field geometry of the parent cloud. In general, most clump properties have a slight trend with clump mass but are independent of (or only very weakly dependent on) the properties of the parent cloud. We conclude that stars are born from a wide variety of environments and there is not a single universal star-forming clump.

Application of sensitivity analysis in extension, inflation, and torsion of residually stressed circular cylindrical tubes

This paper deals with applying two main sensitivity analysis (SA) methods, namely, the Sobol method and the Fourier Amplitude Sensitivity Test (FAST) method on the problem of mixed extension, inflation, and torsion of a circular cylindrical tube in the presence of residual stress. The mechanical side of the problem was previously proposed by Merodio & Ogden (2016). The input parameters in the form of the initial cylinder geometry, the amount of the residual stress, the azimuthal stretch, the axial elongation, and the torsional strain are distributed according to three probability distribution methods, namely the uniform, the gamma, and the normal distribution. In the present work, through applying Sobol and FAST methods, the most influential factors among input parameters on the output variable have been determined. The assessment of our results is then determined by the computation of bias and standard deviation of Sobol and FAST indices for each input parameter in the model.

Simulation of the Void Shape Evolution of High-Temperature Annealed Silicon Structures by means of a Custom Level-Set Formulation

The control and prediction of morphological changes in annealed void microstructures is an essential and powerful tool for different semiconductor applications, for example, as part of the production of pressure sensors, resonators, or other silicon structures. In this work, with a focus on the void shape evolution of silicon, a novel simulation approach based on the level-set method is introduced to predict the continuous transformation of initial etched nano/micro-sized cylindrical structures at different annealing conditions. The developed model, which is based on a surface diffusion formulation and built in COMSOL Multiphysics® (Stockholm, Sweden), is introduced and compared to experimental literature data as well as with other analytical approaches. Some advantages of the presented model include the capability of simulating other materials under similar phenomena, the simulation of any possible initial geometry, and the visualization of intermediate steps during the annealing processing.

Correlations between flow and transverse momentum in Xe+Xe and Pb+Pb collisions at the LHC with the ATLAS detector: A probe of the heavy-ion initial state and nuclear deformation

The correlations between flow harmonics $v_n$ for $n=2$, 3 and 4 and mean transverse momentum $[p_\mathrm{T}]$ in $^{129}$Xe+$^{129}$Xe and $^{208}$Pb+$^{208}$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$ TeV and 5.02 TeV, respectively, are measured using charged particles with the ATLAS detector. The correlations are sensitive to the shape and size of the initial geometry, nuclear deformation, and initial momentum anisotropy. The effects from non-flow and centrality fluctuations are minimized, respectively, via a subevent cumulant method and event activity selection based on particle production in the very forward rapidity. The results show strong dependences on centrality, harmonic number $n$, $p_{\mathrm{T}}$ and pseudorapidity range. Current models describe qualitatively the overall centrality- and system-dependent trends but fail to quantitatively reproduce all the data. In the central collisions, where models generally show good agreement, the $v_2$-$[p_\mathrm{T}]$ correlations are sensitive to the triaxiality of the quadruple deformation. The comparison of model to the Pb+Pb and Xe+Xe data suggests that the $^{129}$Xe nucleus is a highly deformed triaxial ellipsoid that is neither a prolate nor an oblate shape. This provides strong evidence for a triaxial deformation of $^{129}$Xe nucleus using high-energy heavy-ion collision.

Effect of the shot-to-shot variation on charge migration induced by sub-fs x-ray free-electron laser pulses

X-ray free-electron lasers (XFELs) are now able to provide tunable pairs of intense sub-fs pulses in the soft x-ray regime, paving the way for time-resolved investigations of attosecond charge migration in molecules. However, the stochastic shot-to-shot variation of the XFEL pulses may degrade and eventually hide the observable features. We show by means of state-of-the-art calculations that the damping of the charge migration induced by 260 eV pulses in p-aminophenol due to the shot-to-shot variation of pulses generated at the Linac Coherent Light Source is negligible in comparison to the natural damping due to the intrinsic fluctuation of the initial molecular geometry. This result gives us confidence in the utility of XFEL sub-fs pulses for the measurement of charge migration and other ultrafast charge dynamics.

Model study on Υ(nS) modification in small collision systems

Quarkonium production has been studied extensively in relativistic heavy-ion collision experiments to understand the properties of the quark-gluon plasma. The experimental results on the yield modification in heavy-ion collisions relative to that in $p+p$ collisions can be described by several models considering dissociation and regeneration effects. A yield modification beyond initial-state effects has also been observed in small collision systems such as $p+\mathrm{Au}$ and $p+\mathrm{Pb}$ collisions, but it is still premature to claim any hot medium effect. A model study in various small collision systems such as $p+p$, $p+\mathrm{Pb}$, $p+\mathrm{O}$, and $\mathrm{O}+\mathrm{O}$ collisions will help quantitatively the understanding of nuclear effects on the $\mathrm{\ensuremath{\Upsilon}}(nS)$ production. A theoretical calculation considering the gluo-dissociation and inelastic parton scattering for dissociation, and their inverse reaction for regeneration, reasonably describes the modification of $\mathrm{\ensuremath{\Upsilon}}(1S)$ in $\mathrm{Pb}+\mathrm{Pb}$ collisions. Based on this calculation, a Monte Carlo simulation considering the dissociation effect is developed to more realistically incorporate the medium produced in heavy-ion collisions with event-by-event initial collision geometry and hydrodynamic evolution. We extend this framework to small systems to study the medium effects. In this work, we quantify the nuclear modification factor of $\mathrm{\ensuremath{\Upsilon}}(nS)$ as a function of charged particle multiplicity ($d{N}_{ch}/d\ensuremath{\eta}$) and transverse momentum. We also calculate the elliptic flow of $\mathrm{\ensuremath{\Upsilon}}(nS)$ in small collision systems.

Predicting non-axisymmetric growth and facet evolution during lithiation of crystalline silicon anode particles through orientation-dependent interface reaction

A finite deformation modeling framework is developed to capture the experimentally observed two-phase, non-axisymmetric growth during the first lithiation of crystalline silicon cylinder in an improved fashion. The key feature of this model is an orientation-dependent interface reaction constant. Furthermore, the migration of lithium through the lithium-rich, growing amorphous zone is modeled through two additional features. First, an alloying–dealloying reaction that distinguishes between “movable” and “immovable” lithium parts. Second, a strong two-way coupling between diffusion and stress in contrast to existing mathematical models of non-axisymmetric growth. These features enable the prediction of a non-uniform distribution of concentration and stresses. The most important ability of this framework is that it can capture the evolution of facets at the crystalline–amorphous interface shown in experimental studies. The ensuing orientation-dependent interface velocity breaks the axisymmetric shape of the nanowire despite the initial circular geometry and the maintenance of an axisymmetric lithium influx. A very interesting finding is that the deposition of lithium and induced stresses are higher at the sites with lower interface velocity, which occur at the junction of two facets. The resulting stress concentration, in turn, pushes towards the further accumulation of lithium at those sites. It is expected that the improved modeling capabilities of this framework will contribute a step in moving beyond the limitations of simplistic structural design of lithium-ion battery particles.

Theoretical investigation of Aryl/Alkyl halide reduction with hydrated electrons from energy and AIMD aspects.

In this study, the reactions of hydrated electron (e-(aq)) with alkyl and aryl halides were simulated with an ab initial molecular dynamics (AIMD) method to reveal the underlying mechanism. An original protocol was developed for preparing the proper initial wavefunction guess of AIMD, in which a single electron was curled in a tetrahedral cavity of four water molecules. Our results show that the stability of e-(aq) increases with the hydrogen bond grid integrity. The organic halides prefer to react with e-(aq) in neutral or alkaline environment, while they are more likely to react with hydrogen radical (the product of e-(aq) and proton) under acidic conditions. The reaction between fluorobenzene/fluoromethane and hydrogen radical is considered as the least favorable reaction due to the highest reaction barriers. The bond dissociation energy (BDE) suggested that the cleavage of the carbon-halogen bond of their anion radical might be a thermodynamically favorable reaction. AIMD results indicated that the LUMO or higher orbitals were the e-(aq) migration destination. The transplanted electron enhanced carbon-halogen bond vibration intensively, leading to bond cleavage. The solvation process of the departing halogen anions was observed in both fluorobenzene and fluoromethane AIMD simulation, indicating that it might have a significant effect on enthalpy. Side reactions and byproducts obtained during the AIMD simulation suggested the complexity of the e-(aq) reactions and further investigation was needed to fully understand the reaction mechanisms. This study provided theoretical insight into the pollutant environmental fate and constructed a methodological foundation for AIMD simulation of analogous free radical reactions. The theoretical calculation was conducted on the combination of Gaussian16 and ORCA5.0.3 software packages. The initial geometries, as well as the wavefunction initial guesses, were obtained at PBE0/ma-def2-TZVP/IEFPCM-water level in Gaussian16 unless otherwise stated. AIMD simulations were performed at the same level in ORCA. Wavefunction analysis was carried out with Multiwfn. The details methods were described in the section "Computational details" section.

Experimental investigation of flexural buckling behaviour of self-compacting lightweight concrete-filled cold-formed built-up box section (CFBBS) columns

This paper presents an experimental investigation of the flexural buckling behaviour and resistance of innovative self-compacting lightweight concrete (LWSCC)-filled cold-formed built-up box section (CFBBS) columns. A series of sixteen LWSCC-filled CFBBS columns and four reference hollow columns formed by two nested asymmetric lipped channel sections using breakstem rivets at flanges with various member relative slendernesses ratios, concrete strengths and section sizes were tested under pin-ended boundary conditions. Material tests and initial global geometry imperfection measurements were carried out and reported in present study. The failure modes and deformation developments, lateral deflection distribution along the column specimens, flexural buckling resistance and load-end shortening relationship of the specimens were scrutinised and discussed concerning the effect of parameters and the associated coupling effects. Furthermore, a comprehensive strain analysis was conducted and reported based on the longitudinal and lateral strain developments at both compression and tension zones under flexure; it was found that the composite action abated as the member length increased. Finally, as there is no existing design codes for LWSCC-filled CFBBS columns, the experimental results were used to evaluate the applicability of relevant international codified provisions, including Eurocode (EC4), Australia/New Zealand Standard (AS/NZS 2327) and America Specification (AISC 360-16). It was found that AS/NZS 2327 yielded the most accurate and moderately scattered predictions while the predictions from EC4 were found to be the most scattered but with reasonable accuracy and those from AISC 360-16 were overly conservative, albeit the least scattered among these design codes.

Probing initial geometrical anisotropy and final azimuthal anisotropy in heavy-ion collisions at Large Hadron Collider energies through event-shape engineering

Anisotropic flow is accredited to have effects from the initial state geometry and fluctuations in the nuclear overlap region. The elliptic flow (${v}_{2}$) and triangular flow (${v}_{3}$) coefficients of the final state particles are expected to have influenced by eccentricity (${ϵ}_{2}$) and triangularity (${ϵ}_{3}$) of the participants, respectively. In this work, we study ${v}_{2}$, ${v}_{3}$, ${ϵ}_{2}$, ${ϵ}_{3}$, and the correlations among them with respect to event topology in the framework of a multiphase transport model (AMPT). We use transverse spherocity and reduced flow vector as event shape classifiers in this study. Transverse spherocity has the unique ability to separate events based on geometrical shapes, i.e., jetty and isotropic, which pertain to pQCD and non-pQCD domains of particle production in high-energy physics, respectively. We use the two-particle correlation method to study different anisotropic flow coefficients. We confront transverse spherocity with a more widely used event shape classifier--reduced flow vector (${q}_{n}$) and they are found to have significant (anti)correlations among them. We observe significant spherocity dependence on ${v}_{2}$, ${v}_{3}$, and ${ϵ}_{2}$. This work also addresses transverse momentum dependent crossing points between ${v}_{2}$ and ${v}_{3}$, which varies for different centrality and spherocity percentiles.