Computer Simulation Research Articles

Cognitive Technology to Evaluate the Academic Learning of Computational Cognition in Psychology Students

<p style="text-align:justify">This study illustrated an alternative way to evaluate students’ academic learning. It involved the joint and intertwined application of the natural semantic network technique, computer simulations, and semantic priming experiments to assess the cognitive changes in knowledge structures due to academic learning in two groups of psychology students. The experimental group was enrolled in a course on computational cognition, while the control group was oblivious to this course. The results indicated that the cognitive assessment tools discriminate the cognitive changes produced as a result of general training undertaken in a psychology degree versus the influence of a specific course. After the course, the experimental group increased their technical vocabulary, changed their conceptual valuation of definers related to computational theories of mind, and reorganized the relations among definers according to the computational cognition approach. Also, this group presented a higher connectivity index between the concepts of the semantic network, their conceptual activation level and conceptual co-activation pattern changed, and their access level to the evaluated schema’s concepts improved. In contrast, the control group did not show significant changes in their cognitive patterns after the course. These findings suggest that cognitive tools may be helpful in the diagnosis of academic learning.</p>

Golden lion tamarin metapopulation dynamics five years after heavy losses to yellow fever.

The golden lion tamarin (GLT) is an Endangered primate endemic to Brazil's lowland Atlantic Forest. After centuries of deforestation and capture for the pet trade, only a few hundred individuals survived, all in isolated forest fragments 85 km from Rio de Janeiro city. Intensive conservation actions, including reintroduction of zoo-born tamarins, increased numbers to about 3700 in 2014. The most severe yellow fever epidemic/epizootic in Brazil in 80 years reduced two of the largest GLT populations by over 90%. Herein we report the results of a 2023 survey of GLTs designed to examine the dynamics of population recovery following yellow fever. Results indicate that populations hard hit by yellow fever are recovering due in part to immigration from adjacent forest fragments. No local extirpations were observed. About 4800 GLTs live in the survey area. This represents a 31% increase since the baseline survey completed in 2014. Two factors explain most of the increase: four large areas that had no GLTs or very low-density populations in 2014 are now at moderate density (three areas) or low density (one area), explaining 71% of overall increase since 2014. Increase in forest area within our survey area may explain up to 16% of the increase in GLT numbers since 2014. Results of computer simulations suggest that strengthening forest connectivity will facilitate metapopulation resilience in the face of mortality factors such as yellow fever.

Kinetic pathway of HIV-1 TAR cotranscriptional folding.

The Trans-Activator Receptor (TAR) RNA, located at the 5'-end untranslated region (5' UTR) of the human immunodeficiency virus type 1 (HIV-1), is pivotal in the virus's life cycle. As the initial functional domain, it folds during the transcription of viral mRNA. Although TAR's role in recruiting the Tat protein for trans-activation is established, the detailed kinetic mechanisms at play during early transcription, especially at points of temporary transcriptional pausing, remain elusive. Moreover, the precise physical processes of transcriptional pause and subsequent escape are not fully elucidated. This study focuses on the folding kinetics of TAR and the biological implications by integrating computer simulations of RNA folding during transcription with nuclear magnetic resonance (NMR) spectroscopy data. The findings reveal insights into the folding mechanism of a non-native intermediate that triggers transcriptional pause, along with different folding pathways leading to transcriptional pause and readthrough. The profiling of the cotranscriptional folding pathway and identification of kinetic structural intermediates reveal a novel mechanism for viral transcriptional regulation, which could pave the way for new antiviral drug designs targeting kinetic cotranscriptional folding pathways in viral RNAs.

The influence of frequency and gravity on the orientation of active metallo-dielectric Janus particles translating under a uniform applied alternating-current electric field.

Theoretical and numerical models of active Janus particles commonly assume that the metallo-dielectric interface is parallel to the driving applied electric field. However, our experimental observations indicate that the equilibrium angle of orientation of electrokinetically driven Janus particles varies as a function of the frequency and voltage of the applied electric field. Here, we quantify the variation of the orientation with respect to the electric field and demonstrate that the equilibrium position represents the interplay between gravitational, electrostatic and electrohydrodynamic torques. The latter two categories are functions of the applied field (frequency, voltage) as well as the height of the particle above the substrate. Maximum departure from the alignment with the electric field occurs at low frequencies characteristic of induced-charge electrophoresis and at low voltages where gravity dominates the electrostatic and electrohydrodynamic torques. The departure of the interface from alignment with the electric field is shown to decrease particle mobility through comparison of freely suspended Janus particles subject only to electrical forcing and magnetized Janus particles in which magnetic torque is used to align the interface with the electric field. Consideration of the role of gravitational torque and particle-wall interactions could account for some discrepancies between theory, numerics and experiment in active matter systems.

Retrofitting Shear Critical Beams using Ultra High Performance Fibre Reinforced Concrete (UHPFRC)

Ultra High-Performance Fiber Reinforced Concrete (UHPFRC) is a cementitious composite that exhibits superior mechanical properties, durability, fire resistance, abrasion resistance, and chloride penetration. The enhanced performance of UHPFRC is attributed to the presence of highstrength steel fibers. Therefore, UHPFRC is widely used in structural retrofitting and rehabilitation works to improve the load carrying capacity of deteriorated structural members. This paper investigates the behaviour of UHPFRC retrofitted shear critical reinforced concrete beams. Numerical models were developed to simulate how the load-carrying capacity of UHPFRC retrofitted shear critical beams is influenced by factors such as jacket configuration, jacket thickness, and jacket length along the beam. Numerical models were validated using pre-existing experimental results. A modified Concrete Damage Plasticity (CDP) model was employed to simulate the material behaviour of UHPFRC. The validated numerical model was employed to perform parametric studies to examine the behaviour of UHPFRC retrofitted beams. It was observed that the modified CDP model effectively predicted the UHPFRC behaviour. Further, the results indicated that the application of UHPFRC retrofitting converted the brittle shear failure of shear-critical reinforced concrete beams into flexure failure. Moreover, the load carrying capacity of retrofitted beams increased with the retrofitted UHPFRC jacket thickness.

Quantitative risk assessment of gas leakage and explosion in open kitchens and partitioned kitchens

ABSTRACT In recent years, natural gas companies have faced more and more gas supply applications for open kitchens in China. However, natural gas cannot be utilized in open kitchens according to the current compulsory regulations. The numerical models for three typical open kitchen layouts and the corresponding partition kitchen layouts were developed, respectively. The experimental setup of gas leakage and explosion, like a residential kitchen, was established based on the similarity theory. The accuracy and reliability of numerical models have been validated by three sets of experiments. An innovative quantitative risk assessment method was proposed to quantify the integrated risks for the open kitchen layout and the partition kitchen layout. The effectiveness of the proposed risk reduction measures was assessed using a modified LOPA (i.e. Layer Of Protection Analysis). The results show that the integrated risk for the open kitchen layout in different apartments is 1.37 ~ 4.65 times than that for the partition kitchen layouts. The integrated risk of gas leakage explosion in three open kitchen layout arrangements was reduced by 94.8%, 50%, and 94.5%, respectively, by setting two layers of protection. Meanwhile, the increased expense of ¥400 can be generally acceptable for the majority of residential users. The achievements could provide theoretical and technological guidance for gas safety supply in open kitchens.

Computational fluid dynamics numerical simulation of flue gas emission from stack and tower integration system of coal-fired power plant

ABSTRACT The method of Computational Fluid Dynamics (CFD) simulation has been extensively employed in the stack and tower integration technology (STIT) research; however, a significant number of studies overlooked the impact of thermal buoyancy on the external flow field of cooling tower. In light of this, an improved approach is proposed in this study. A model of a cooling tower and its surrounding flow field was established, and its reliability was confirmed too. Based on our model, the performance of three enhancement strategies under various crosswind speeds and ambient temperatures was simulated. The results indicate that all three enhancement strategies can effectively simulate the effects of thermal buoyancy. In the simulations, the elevation of the flue gases increased from 306 m to either 426 m or 476 m. In the present study, ambient conditions characterized by crosswind speeds below 4 m/s and temperatures below 297.15 K were deemed suitable for the dispersion of stack and tower integration (STI) flue gases. A power function distribution was identified between crosswind speed and the mean height of the plume, while a linear relationship was observed between ambient temperature and the mean height of the plume.

A one-dimensional computational model for blood flow in an elastic blood vessel with a rigid catheter.

Strokes are one of the leading causes of death in the United States. Stroke treatment involves removal or dissolution of the obstruction (usually a clot) in the blocked artery by catheter insertion. A computer simulation to systematically plan such patient-specific treatments needs a network of about 105 blood vessels including collaterals. The existing computational fluid dynamic (CFD) solvers are not employed for stroke treatment planning as they are incapable of providing solutions for such big arterial trees in a reasonable amount of time. This work presents a novel one-dimensional mathematical formulation for blood flow modeling in an elastic blood vessel with a centrally placed rigid catheter. The governing equations are first-order hyperbolic partial differential equations, and the hypergeometric function needs to be computed to obtain the characteristic system of these hyperbolic equations. We employed the Discontinuous Galerkin method to solve the hyperbolic system and validated the implementation by comparing it against a well-established 3D CFD solver using idealized vessels and a realistic truncated arterial network. The results showed clinically insignificant differences in steady flow cases, with overall variations between 1D and 3D models remaining below 10%. Additionally, the solver accurately captured wave reflection phenomena at domain discontinuities in unsteady cases. A primary advantage of this model over 3D solvers is its ease in obtaining a discretized geometry of complex vasculatures with multiple arterial branches. Thus, the 1D computational model offers good accuracy and applicability in simulating complex vasculatures, demonstrating promising potential for investigating patient-specific endovascular interventions in strokes.

Electromagnetic–thermal–mass transport triple hybrid model for energy-efficient hydrogen release from metal particles by induction heating

Hydrogen storage in metals is anticipated to be a highly promising technical approach for managing hydrogen in diverse energy applications, emphasizing the need to establish efficient operating conditions. In this study, we developed a numerical model that can simultaneously calculate hydrogen and heat transport combined with electromagnetic induction heating of metal particles. Using the developed numerical simulator, we investigated the behavior of the hydrogen release process from the hydrogen-absorbing metal and proposed important indicators for the operation. The fractions of the electromagnetic energy absorbed by the metal particle used for the hydrogen release, sensible heat, interfacial heat conduction, and thermal radiation were systematically evaluated. Considering the trade-off between temperature rise and the hydrogen concentration gradient, an optimal diameter of metal particles existed for the maximum hydrogen release rate. Similarly, the trade-off between temperature rise and energy consumption revealed an optimal electromagnetic power density for the heat utilization fraction for hydrogen release. Our electromagnetic–thermal–mass transport triple hybrid model constitutes a useful numerical simulator for the design of energy-efficient hydrogen storage systems.

GOLD PLASMONIC ARRAY STRUCTURES FOR SENSING APPLICATIONS

This article is devoted to the theoretical study of the plasmonic properties of periodically arranged arrays of gold nanoparticles. The Comsol Multiphysics software, which is based on the finite element method, was used to build 3D numerical models for the simulation and conduct research. In this work the electric field distribution and optical characteristics of the spherical gold nanoparticles array were studied. Individual localized surface plasmon resonance modes are influenced when metallic nanoparticles are in the close proximity and as a result the electric near- fields can couple, resulting in a new hybrid mode. We mainly focused here on the investigation of two crucial questions, particularly, influences of the gap between the nanoparticles and the refractive index of the surrounding medium on the resulting optical response of the gold nanoparticles arrays. The array of periodically arragement gold nanoparticles is characterized by an enhanced local electric field between the nanoparticles, which is inversely proportional to the gap between the particles. The field strength and optical properties (reflection, transmission, and absorption) can be conveniently manipulated by changing the gap between particles. In additional, their potential applications as sensetive plasmonic sensors element have been considered. The studied structure has a significant potential for practical applications due to its wide range of the operating wavelengths and ease of the high-throughput fabrication. In the course of the study, it was established that the change in the distance between the surface of nanoparticles by 1 nm leads to a significant shift in the spectral transmission and reflection curves on the spectral range. In addition, these studies showed that an increase in the distance between the surfaces of nanoparticles leads to the decrease in the near-field interaction between gold nanoparticles in the array. Therefore, the obtained results can be successfully used in the manufacture of highly sensitive plasmon sensors with the possibility of controlling the sensitivity and the working spectral range.

Application of Intercritical Austenitizing in a Commercial CMnSi Steel as a Tool for Optimizing a One‐Step Quenching and Partitioning Cycle Aiming to Achieve a Third‐Generation Advanced High‐Strength Steel

Advanced high‐strength steels (AHSS) have been extensively studied to develop its third generation from relatively low‐cost alloys, but seeking optimized mechanical properties. In this context, the effects of quenching heat treatments are evaluated in this work after intercritical austenitizing (IA) on microstructure, alloying elements partitioning, and Ms temperature for a commercial CMnSi alloy. Applying dilatometric data and microstructural characterization, different heat cycles are evaluated. The obtained experimental results are compared with those ones obtained by computer simulations at equilibrium conditions. Based on this characterization, an optimized one‐step quenching and partitioning (Q&P) cycle (after IA) is proposed and applied to tensile test specimens. Then, the specimen microstructure is characterized by scanning and transmission electron microscopy as well as by X‐ray diffraction. Using the proposed methodology, it is possible to produce a Q&P steel with a product of tensile strength and elongation of 29.5 GPa% and a 7% volumetric fraction of retained austenite. It is concluded that the precise knowledge about the IA effects on the phase transformations and microstructure evolution in a commercial CMnSi alloy has great potential to be applied in defining a one‐step Q&P heat treatment that favors a multiphase microstructure, which meets mechanical properties requirements for a third‐generation AHSS.

Answering the key stakeholder questions about the impact of offshore wind farms on marine life using hypothesis testing to inform targeted monitoring

Abstract Stakeholders need scientific advice on the environmental impacts of offshore wind (OW) before the facilities are installed. The utility of conventional environmental monitoring methods as a basis for forecasting OW impacts is limited because they do not explain the causes of the observed effects. We propose a multistep approach, based on process-oriented hypothesis testing, targeted monitoring and numerical modeling, to answer key stakeholder questions about planning an OW facility: Q1—Where do we place future OW farms so that impacts on the ecosystem are minimized? Q2—Which species and ecosystem processes will be impacted and to what degree? Q3—Can we mitigate impacts and, if so, how? and Q4—What are the risks of placing an OW facility in one location vs. another? Hypothesis testing can be used to assess impacts of OW facilities on target species-ecological process. This knowledge is transferable and is broadly applicable, a priori, to assess suitable locations for OW (Q1). Hypothesis testing can be combined with monitoring methods to guide targeted monitoring. The knowledge generated can identify the species/habitats at risk (Q2), help selecting/developing mitigation measures (Q3), and be used as input parameters for models to forecast OW impacts at a large spatial scale (Q1; Q4).

A new analytical model for transient heat transfer modeling of geothermal monotube heat exchangers

In this study, we present a new analytical model for the analysis of transient heat transfer (the model is solved after Laplace transformation) in geothermal monotube heat exchangers (GHE). The model accounts for various factors, including the heat exchanger's geometric parameters, the nature of the fluid (air and water), flow characteristics (laminar and turbulent), and heat transfer boundary conditions. Initially, the model's performance is validated by comparing its results with those obtained from computational fluid dynamics simulations using OpenFOAM. This validation process ensures the reliability and accuracy of the model. Additionally, an analysis of the heat transfer mechanisms and key modeling parameters identified from the comparison is provided. In the subsequent section, the analysis is extended by comparing the proposed model to four existing analytical models available in the literature. These reference models employ distinct approaches to simulate heat transfer to the ground. By examining a range of cases, the performance of the model is systematically evaluated against these conventional methods. This work closes by an analysis of the analytical models and the impact on the accuracy of the results highlighting the advantages of the proposed method in geothermal applications.

Simulating the sealing performance of the double rubber cylinder assembly in an intelligent pipeline isolation tool

Intelligent pipeline isolation tools (IPITs) are widely used for pipeline maintenance and repair. Therefore, authors mainly study the sealing performance of double rubber cylinder IPIT. This study first analyzed the material and geometric properties of the rubber cylinders in an IPIT to establish a numerical finite element model of cylinder mechanical behavior. The influence of the cylinder hardness, camber angle, and short-side length on the sealing performance was subsequently investigated by systematically altering the established model according to the control variable method. Next, the response surface methodology was employed to evaluate the change in model sealing performance according to the coupled action of multiple rubber cylinder parameters and identify their optimal values.

Topology Reconfiguration of Anion-Pillared Metal-Organic Framework from Flexibility to Rigidity for Enhanced Acetylene Separation.

Flexible metal-organic framework (MOF) adsorbents commonly encounter limitations in removing trace impurities below gate-opening threshold pressures. Topology reconfiguration can fundamentally eliminate intrinsic structural flexibility, yet remains a formidable challenge and is rarely achieved in practical applications. Herein, we present a solvent-mediated approach to regulate the flexible CuSnF6-dpds-sql (dpds = 4,4''-dipyridyldisulfide) with sql topology into rigid CuSnF6-dpds-cds with cds topology. Notably, the cds topology is unprecedented and firstly obtained in anion-pillared MOF materials. As a result, rigid CuSnF6-dpds-cds exhibits enhanced C2H2 adsorption capacity of 48.61 cm3 g-1 at 0.01bar compared to flexible CuSnF6-dpds-sql (21.06 cm3 g-1). The topology transformation also facilitates the adsorption kinetics for C2H2, exhibiting a 6.5-fold enhanced diffusion time constant (D/r2) of 1.71 × 10-3 s-1 on CuSnF6-dpds-cds than that of CuSnF6-dpds-sql (2.64 × 10-4 s-1). Multiple computational simulations reveal the structural transformations and guest-host interactions in both adsorbents. Furthermore, dynamic breakthrough experiments demonstrate that high-purity C2H4 (>99.996%) effluent with a productivity of 93.9mmol g-1 can be directly collected from C2H2/C2H4 (1/99, v/v) gas-mixture in a single CuSnF6-dpds-cds column. This article is protected by copyright. All rights reserved.

Left-handed metamaterial based on circular split ring (CSRR) resonator for microwave sensing Application

This paper presents a new metamaterial structure specifically designed to operate in the L, S, and C frequency bands. It is characterized by a small unit cell size of 15mm × 15 mm. The metamaterial's electromagnetic properties are thoroughly examined, utilizing FR-4 substrate material and copper circular split ring resonators (CSRRs). The Computer Simulation Technology (CST) software uses the finite integration technique (FIT) to precisely model the effective parameters over a frequency range of 0–6 GHz. In simulations and experiments, the structure demonstrates negative refractive index, effective permittivity, and effective permeability. The electric and magnetic field distributions within the unit cell are accurately characterized using vector fields. In addition, the equivalent circuit is simulated and depicted using ADS software, with comparisons drawn between the measured data and the simulated data. The experimental validation, conducted using six varying thicknesses of FR4 materials, verifies the resemblance between the simulated and the measured transmission coefficients. Moreover, the effective medium ratio (EMR) of the metamaterial is calculated to be 12.74, indicating its promising capabilities for microwave sensing applications. The examination of the sensor model uncovers such metrics as quality factors, frequency detection resolution (FDR) values, and sensitivities, all of which enhance our comprehension of the material's performance. This discovery has the potential to advance the development of sensing metamaterials, which could significantly impact various applications and enhance research in the field.

Self-reverting vortices in chiral active matter

There is currently a strong interest in the collective behavior of chiral active particles that can propel and rotate themselves. In the presence of alignment interactions for many chiral particles, chiral self-propulsion can induce vortex patterns in the velocity fields. However, these emerging patterns are non-permanent, and do not induce global vorticity. Here we combine theoretical arguments and computer simulations to predict a so-far unknown class of collective behavior. We show that, for chiral active particles, vortices with significant dynamical coherence emerge spontaneously. They originate from the interplay between attraction interactions and chirality in the absence of alignment interactions. Depending on parameters, the vortices can either feature a constant vorticity or a vorticity that oscillates periodically in time, resulting in self-reverting vortices. Our results may guide future experiments to realize customized collective phenomena such as spontaneously rotating gears and patterns with a self-reverting order.

Large-scale engineered meta-barriers for attenuation of seismic surface waves

This study evaluates the performance of large-scale meta-barriers in attenuating seismic surface waves and transportation-induced vibrations in the most disastrous frequency range of 0–30 Hz. By developing analytical and three-dimensional numerical models, it evaluates the properties of the proposed meta-barrier and presents their effects on the attenuation range. Moreover, it discusses a simplified mass-spring-mass model of the meta-barrier, demonstrating that the attenuation range of a unit cell can be approximated using this model. The proposed design consists of three-dimensional two-layers (3D-2C) unit cells arranged periodically with different configurations to be placed between the wave source and structure. Specifically, the meta-barriers can be arranged gradually (periodic spacing along the length), widening the attenuation range to block nearly 85% of the most devastating waves using typically arranged stacked unit cells and triangular-like arrangement (double wedge). The results show that a typical stacked unit cells reflect the incoming waves towards the source, while using the double wedge design, the surface wave can be converted to bulk wave, thereby reducing the risk to the surroundings. Moreover, the study validates the attenuation range using three-dimensional time history analysis subjected to an artificial wavelet (Ormsby wavelet) and three actual seismic records (1975 Oroville, 1984 Bishop, and 2001 Anza time histories).

Cyclic behaviour of welded stainless steel beam-to-column connections: Experimental and numerical study

This paper presents an experimental and numerical programme on six welded stainless steel beam-to-column connections subjected to cyclic loading. The test specimens were designed in accordance with Eurocodes and comprised an I-section beam made from 316 L stainless steel welded to an I-section column made from 304 L stainless steel. Each specimen was subjected to a quasi-static cyclic loading protocol and the load-displacement curves are monitored and reported. The results are analysed in terms of failure characteristics, skeleton curve, strain distribution and energy dissipation. Typical failure modes are combined global flexural and torsional buckling and localised web and flange buckling of the beams. The slope of skeleton curve in the hardening region and the energy dissipation capacity appeared to reduce with the section size. Numerical models capable of successfully replicating the experimentally observed response were developed. The load-displacement behaviour and the failure pattern were compared to the experimental ones, showing a good validation. Overall, it has been demonstrated that good hysteretic performance has been achieved for the welded stainless steel beam-to-column connections.

Experiments and numerical modelling of secondary flows of blood and shear-thinning blood analogue fluids in rotating domains

AbstractThe transition from concentric primary flow to non-tangential secondary flow of blood was investigated using experimental steady shear rheometry and numerical modelling. The aims were to: assess the difference in secondary flow in a Newtonian versus shear-thinning blood analogue; and measure the secondary flow in the blood. Both experiments and numerical modelling showed that the transition from primary to secondary flow was the same in a Newtonian fluid and a shear-thinning blood analogue. Experiments showed whole blood transitioned to secondary flow at lower modified Reynolds numbers than the Newtonian fluid; and transition was haematocrit dependent with higher RBC concentrations transitioning at lower modified Reynolds numbers. These results indicate that modelling blood as a purely shear-thinning fluid does not predict the correct secondary flow fields in whole blood; non-Newtonian effects beyond shear-thinning behaviour are influential, and incorporating effects such as multiphase contributions and viscoelasticity, yield stress and thixotropy is necessary.