Advanced Simulation Model Research Articles

A Novel Approach for Simulation and Optimization of Rubber Vulcanization

The kinetic model, encompassing the curing and reversion phenomena of the NR/SBR rubber vulcanization process, was developed by means of the finite element method simultaneously with heat transfer equations, including heat generation due to curing reactions. The vulcanization simulation was conducted for three spheres of different diameters (1, 5 and 10 cm) and two rubber wheels, one of which was a commercial product of the rubber industry. The proposed advanced simulation model, based on products' two-dimensional axisymmetry, includes cooling after vulcanization, during which the crosslinking reactions continue to take place as a result of the products' heated interiors. As a criterion for removing the product from the mold, an average vulcanization degree of 0.9 was set, whereby, during cooling, the vulcanization degree increases, due to crosslinking reactions. Based on the minimal difference between the maximal and minimal vulcanization degrees, which did not exceed a value of 0.0142, the optimal process parameters for each product were determined, achieving homogeneity and obtaining high-quality rubber products, while simultaneously ensuring a more efficient vulcanization process and enhanced cost effectiveness for the rubber industry.

Probabilistic Validation: Theoretical Foundation and Methodological Platform

Abstract Addressing safety concerns in commercial nuclear power plants (NPPs) often requires the use of advanced modeling and simulation (M&S) in association with the probabilistic risk assessment (PRA). Advanced M&S are also needed to accelerate the analysis, design, licensing, and operationalization of advanced nuclear reactors. However, before a simulation model can be used for PRA, its validity must be adequately established. The objective of this research is to develop a systematic and scientifically justifiable validation methodology, namely, probabilistic validation (PV), to facilitate the validity evaluation (especially when validation data are not sufficiently available) of advanced simulation models that are used for PRA in support of risk-informed decision-making and regulation. This paper is the first in a series of two papers related to PV that provides the theoretical foundation and methodological platform. The second paper applies the PV methodological platform for a case study of fire PRA of NPPs. Although the PV methodology is explained in the context of PRA of the nuclear industry, it is grounded on a cross-disciplinary review of literature and so applicable to validation of simulation models, in general, not necessarily associated with PRA or nuclear applications.

Model-based NVH optimization of a tractor drivetrain during different phases of a design adaption

The modern, ever shorter development process of powertrains incorporates many disciplines of mechanical engineering. Among these, the dynamic and acoustic behavior—which is often referred to as noise, vibration, harshness (NVH)—is becoming increasingly important for the consumer’s purchase decision. However, NVH is often only considered in the last steps of the product development as both experimental analysis methods and high-fidelity modeling approaches are time-consuming. In contrast, in early phases of the development process, fast iteration cycles are crucial. Thus, the engineer needs appropriate NVH models for each phase of the development process in order to evaluate design and concept decisions with respect to their NVH implications.This publication shows a methodological guide on how to apply suitable NVH models forward directed in different stages of the development process and thus efficiently implement optimizations. In the early, highly iterative phases of the development process, analytical determination of the excitation behavior as well as simplified finite element simulations are carried out in order to estimate the vibration behavior of the concept. For the first elaborated geometries, frequency response functions can then be determined and thus the influence of e.g. ribbings to NVH behavior can be evaluated. In the later phases, where advanced simulation models have to be set up, a fully parameterized eMBS model of the drivetrain enables an analysis of its operating behavior, from which further optimization potential of the system can be derived. The proposed method is demonstrated on the example of a tractor transaxle development process.

Effects of mixed marshalling modes on longitudinal freight train dynamics

Mixed freight trains have more diversified vehicle characteristics and train combination modes than unified freight trains, so it is more difficult for mixed freight trains to predict the accident caused by longitudinal impulse. At present, train dynamics theories and numerical simulation methods have been increasingly used to reduce longitudinal train impulse and decrease freight wagon instability. According to these research experiences, this paper focuses on the marshalling modes of mixed freight trains and their effects on the longitudinal in-rain forces. For this purpose, an advanced simulation model for mixed freight trains was developed and several typical mixed marshalling modes were designed and simulated. The results indicate that, for the mixed train including empty and loaded wagons, empty wagons should be arranged at the tail of the train and should avoid being marshalled together. For the mixed train including marshalled wagons with various actual live loads or nominal axle loads, heavier wagons should be centrally arranged in the front part of the train, and meanwhile marshalled wagons should avoid being sorted by weight in the concave and ascending distribution mode. For the mixed train including marshalled wagons with various body types, container flat wagons and oil tank wagons should be arranged as much as possible in the front of the other wagons.

Embedding R inside the PhysPK Bio-simulation Software for Pharmacokinetics Population Analysis

Abstract Background: PhysPK stands as a flexible and robust bio-simulation and modeling software designed for analysis of population pharmacokinetics (PK) and pharmacodynamics (PD) systems. PhysPK equips users with standard diagnostic plots for pre- and post-analysis to delineate PK and PD within population-based frameworks. Furthermore, PhysPK facilitates the establishment of mathematical models that elucidate the intricate interplay between exposure, safety, and efficacy. Methods: Enhancing simulation modeling capabilities necessitates seamless integration between commercial discrete-event PK and PD simulation tools and external software. This synergy can be amplified by incorporating open-source solutions, like R, which boasts a rich array of comprehensive packages tailored for diverse tasks, including data analysis (ggplot2), scientific computation (stats), application development (shiny), back-end web development (dplyr), and machine learning (CARAT). The integration of R within PhysPK holds the potential to efficiently interpret and analyze PK/PD output and routines using R packages. Results: This article presents a tutorial that highlights the incorporation of R code within PhysPK and the rendering of R scripts within the PhysPK monitor. The tutorial utilizes a two-compartment model for comparison against the analysis developed by Hosseini et al. in 2018 within the context of the gPKPDSim application and WinNonlin® software. The illustrative example that is provided and discussed demonstrate estimated and simulated plots, revealing negligible differences in the significance for CL and CLd (6.89 ± 0.2 and 45.5 ± 17.4 [reference], and 7.06 ± 0.32 and 49.04 ± 9.2 [PhysPK], respectively), as well as volumes V1 and V2 (49.15 ± 3.8 and 34.61 ± 5.2 [reference], and 48.8 ± 3.66, and 33.2 ± 3.95 [PhysPK], respectively). Conclusions: Our study underscores the potential of integrating open-source software, replete with an array of innovative packages, to elevate predictive capabilities and streamline analyses in PK methods. This integration ushers in new avenues for an advanced intelligent simulation modeling within the realm of PK, thus holding significant promise for the advancement of drug research and development.

Metronidazole photocatalytic degradation by zinc oxide nanoparticles synthesized in watermelon peel extract; Advanced optimization, simulation and numerical models using machine learning applications

Antibiotics in water systems and wastewater are among the greatest major public health problem and it is global environmental issues. Herein a novel approach for the photocatalytic degradation of metronidazole (MTZ) by using eco-green zinc oxide nanoparticles (EG-ZnO NPs) which biosynthesised using watermelon peels extracts has been investigated. Mathematical prediction models using an adaptive neuro-fuzzy inference system (ANFIS), artificial neural networks (ANN) and response surface methodology (RSM) were used to determine the optimal conditions for the degradation process. The FESEM analysis revealed that EG-ZnO NPs was white with a spherical shape and size between 40 and 88 nm. The simulation process for the mathematical prediction model revealed that the best validation performance was 55.35 recorded at epoch 2, the coefficient (R2) was 0.9967 for training data, as detected using ANN analysis. The best operating parameters for MTZ degradation was predicted using RSM to be: 170 mg L−1 of EG-ZnO NPs, 20.61 mg 100 mL−1 of MTZ, 10 min exposure time, and a pH of 5, with 77.48 vs 78.14% corresponding to the predicted and empirically measured respectively. The photocatalytic degradation of MTZ was fitted with pseudo-first-order kinetic (R2 > 0.90). MTZ lost the antimicrobial activity against Bacillus cereus (B. cereus) and Escherichia coli (E. coli) after degradation with EG-ZnO NPs at the optimal conditions as determined in the optimization process. These findings reflect the important role ANFIS and ANN in predicting and optimising the efficacy of engineered nanomaterials, including EG-ZnO NPs, for antibiotic degradation.

Personalized image enhancement method for color deficient observers.

A personalized image enhancement method is proposed to improve color vision in hereditary color vision deficiency (CVD). It is divided into two stages: evaluation of CVD and gamut mapping for image enhancement. These two separate stages are connected via a psychophysical experiment, through which the deficiency test result expressed using the C-index can be further transformed into a physical parameter, namely the wavelength shift of the cone fundamental. Experiments conducted by the color-deficient observers (CDOs) validated this proposed method, and it is emphasized that the proposed method is just serving as a template for image enhancement. A more advanced simulation model, a more accurate assessment method, or a more sophisticated gamut mapping algorithm can yield a better result.

Crop phenotyping in a context of global change: What to measure and how to do it.

High-throughput crop phenotyping, particularly under field conditions, is nowadays perceived as a key factor limiting crop genetic advance. Phenotyping not only facilitates conventional breeding, but it is necessary to fully exploit the capabilities of molecular breeding, and it can be exploited to predict breeding targets for the years ahead at the regional level through more advanced simulation models and decision support systems. In terms of phenotyping, it is necessary to determined which selection traits are relevant in each situation, and which phenotyping tools/methods are available to assess such traits. Remote sensing methodologies are currently the most popular approaches, even when lab-based analyses are still relevant in many circumstances. On top of that, data processing and automation, together with machine learning/deep learning are contributing to the wide range of applications for phenotyping. This review addresses spectral and red-green-blue sensing as the most popular remote sensing approaches, alongside stable isotope composition as an example of a lab-based tool, and root phenotyping, which represents one of the frontiers for field phenotyping. Further, we consider the two most promising forms of aerial platforms (unmanned aerial vehicle and satellites) and some of the emerging data-processing techniques. The review includes three Boxes that examine specific case studies.

Numerical Investigation of the Orientability of Single Reinforcement Fibers in Polymer Matrices.

Fiber-reinforced polymers are increasingly being used, especially in lightweight structures. Here, the effective adaptation of mechanical or physical properties to the necessary application or manufacturing requirements plays an important role. In this context, the alignment of reinforcing fibers is often hindered by manufacturing aspects. To achieve graded or locally adjusted alignment of different fiber lengths, common manufacturing technologies such as injection molding or compression molding need to be supported by the external non-mechanical process. Magnetic or electrostatic fields seem to be particularly suitable for this purpose. The present work shows a first simulation study of the alignment of magnetic particles in polymer matrices as a function of different parameters. The parameters studied are the viscosity of the surrounding polymer as a function of the focused processing methods, the fiber length, the thickness and permeability of the magnetic fiber coatings, and the magnetic flux density. The novelty of the presented works is in the development of an advanced simulation model that allows the simulative representation and reveal of the fluid–structure interaction, the influences of these parameters on the inducible magnetic torque and fiber alignment of a single fiber. Accordingly, the greatest influence on fiber alignment is caused by the magnetic flux density and the coating material.

On the Value of LES Models for Evaluating Spatio-Temporal Tropospheric Variability in Multitemporal SAR Interferograms

Atmospheric delay has a profound impact on synthetic aperture radar (SAR) interferometry, inducing a spatial signal that significantly devaluates interferometric products. While the wide-scale variability of the atmosphere can be adequately modeled with global or regional weather models, it is especially the turbulent and convective part of the atmosphere at smaller spatial and temporal scales that is typically poorly captured. Due to the high resolution and precision of InSAR, there is a need for a realistic modelling of the 3D distribution of turbulent refractivity in the boundary layer. This would enable assessment of the impact of a temporal or spatial model misalignment on the interferometric products, and contribute to studying the impact for future SAR missions. Here we test the feasibility of an advanced Large Eddy Simulation (LES) model to simulate a time-series refractivity distribution with a high spatio-temporal resolution to show the spatio-temporal variability of the troposphere on short time scales. We found for a fair-weather situation that the LES model produces realistic atmospheric simulations that match stochastically with results found in interferometric studies and that tropospheric delay variation leads to significant phase gradients within several minutes. This implies that even when using an (unrealistic) perfect weather model with resolutions similar to the SAR image, realizations that are several minutes apart from the time of the SAR acquisition will lead to significant phase errors. We propose the use of LES models as a realistic instrument to perform InSAR quality-assessments and for the development and simulation for future missions.

Reliable crack detection in a rotor system with uncertainties via advanced simulation models based on kriging and Polynomial Chaos Expansion

In this study the authors propose to take into account the nonlinear effects induced by the presence of a transverse crack to carry out vibratory monitoring and detect transverse cracks in rotating systems subject to model uncertainties. More precisely, we focus more particularly on the global complexity of the nonlinear dynamic behaviour of cracked rotors and the evolution of their harmonic components as a function of the parameters of a transverse breathing crack (its position and depth) when numerous uncertainties are considered. These random uncertainties correspond to random geometric imperfections (two disc thicknesses), random material properties (Young modulus and material density) and boundary conditions uncertainty (two bearing stiffnesses). The objective of the present work is to identify robust indicators capable of determining the presence of a crack and its status even though numerous uncertainties are present.To conduct such a study, an advanced surrogate modelling technique based on kriging and Polynomial Chaos Expansion (PCE) is proposed for the prediction of both the critical speeds and the harmonic components n× during passage through sub-critical resonances. An extensive study to ensure the validation of the surrogate models and a relevant choice of both the parametric and random Design of Experiments (i.e. kriging DoE and PCE DoE) is proposed. The proposed methodology is applied on a flexible rotor with a transverse breathing crack and subjected to random geometric imperfections and fluctuations in material properties of the rotor system.

Modeling the behavior of reinforced concrete slabs subjected to impact

In recent years, safety of nuclear power plants against external missile impacts such as those due to tornadoes has gained significant attention. In many cases, advanced simulation tools based on finite element method (FEM) or smooth particle hydrodynamics (SPH) are being employed to simulate missile impact behavior and to evaluate vulnerability of nuclear facilities. Due to the complex nature of impact behavior, it requires appropriate calibration of parameters in the advanced simulation models that are used to represent them. In this manuscript, we propose a novel approach for modeling the behavior of reinforced concrete slabs subjected to missile impact. First, we use data from one experimental study to develop and calibrate various models needed to conduct the finite element analysis. Then, the calibrated models are used to conduct a predictive analysis for a different experimental setup. A comparison of the experiment and the analytical results for the new test provides confidence in the predictive capability of the simulation approach with calibrated parameters.

Case studies of integration between activity-based demand models and multimodal assignment

Aiming at supporting decision makers in transport policy choices in an increasingly complex sequence of activities of our real day-life, this paper investigates the integration between Activity Based Model (ABM) and transport assignment by focusing on the multimodal demand-supply interaction to be used in more advanced simulation models. The consistency between ABM and assignment models is studied proposing a methodology that can be applied to large real size networks. A new formalization of integration of ABM with multimodal assignment is proposed, oriented to an easy-to-use and computationally faster application. The interaction between different modes sharing the same network facilities is considered, as well as crowding (public transport) and congestion (road) phenomena.The application to different real case studies in Qatar and in Rome are presented to show the promising results of the proposed approach for a better transport simulation in urban areas.

Cyclone wind hazard assessments for eastern coastal cities in India using a fast-predictive model

Tropical cyclone wind-induced hazards for the eastern coastal built environments of India can be severe. The extreme cyclone winds can cause damage to structures and infrastructures and losses of lives and economies. The current building code of India provides design wind speeds for the eastern coastal cyclone-prone regions. These design wind speeds were determined without considering extreme wind speeds associated with different weather types, such as thunderstorms or cyclones. The cyclone simulation technique has not been considered to update the design wind speeds for India's eastern coastal cyclone-prone regions. Several previous studies used the regional maximum sustained wind speeds to derive the design level cyclone-induced wind speeds. This approach differs from advanced cyclone simulation techniques and provides overly conservatism. The effect of using the regional maximum sustained wind speeds of cyclones in estimating the design wind speeds was investigated quantitatively in this study. A fast-predictive cyclone wind hazard model was proposed to assess the cyclone wind hazards. This model used simple wind field modeling and directly applied the historical best track datasets. The performance of this model was validated by comparing the predicted design level tropical cyclone wind speeds for selected coastal cities in the USA and China to those provided by the local building code or reported in previous studies using advanced tropical cyclone simulation models. This fast-predictive model was used to calculate the peak cyclone wind speeds and predict the 50-year return period cyclone wind speeds for twenty eastern coastal cities in India. The predicted 50-year return period cyclone wind speeds using the fast-predictive model were compared with those predicted using the regional maximum sustained wind speeds and current code design wind speeds.

Static Performance of a Hydrostatic Thrust Foil Bearing for Large Scale Oil-Free Turbomachines

Abstract This work presents a novel design of a hydrostatic thrust foil bearing (HSTFB), with an outer diameter of 154 mm, along with simulation and test results up to a specific load capacity of 223 kPa (32.3 psi). This bearing has high load capacity, low power loss, and no friction/wear during startup and shutdown. In addition, the HSTFB allows for bidirectional operation. The paper also presents an advanced simulation model that adopts the exact locations of tangentially arranged bumps to a cylindrical two-dimensional plate model of the top foil. This method predicts top foil deflection with better accuracy than the traditional independent elastic foundation model, which distributes the bump locations over the nodal points in the cylindrical coordinates, and with less computational resources than the finite element method applied to the entire bumps/top foils. The presented HSTFB was designed for organic Rankine cycle (ORC) generators, but its performance was predicted and measured using air in this paper. The bearing static performance is compared analytically against the rigid counterpart and presented at different supply pressures, speeds, and minimum film thicknesses. Experimental verification is conducted at 10, 15, and 20 krpm. The measured load capacity and frictional loss agree well with the prediction. The measured film thickness also agrees with the prediction after the structural deflection of the thrust runner disk is compensated. Overall, the novel HSTFB demonstrates excellent static performance and good potential for the intended ORC generators and other large oil-free turbomachines.

Experimental and numerical investigations with environmental impacts of affordable square pyramid solar still

In this work, a square pyramid solar still is designed, fabricated and tested during recommended days at the four seasons of Al Kufa climatic conditions (elevation is 30 m and location is 32° North and 44° East), Iraq. The proposed design of the still can be used at any remote location in Iraq where is no electricity and high solar intensity. Designing the affordable solar still was mainly due to simplicity in its operation process, long life and low cost. Data obtained from an advanced simulation modeling of multi-shaped solar stills are used to determine the temperature gradient and the heat flux distributions during unsteady-state conditions. The procedure of the modelling is included: volumetric properties of the solid and fluid regions, thermal loads on the still, mesh generation, grid convergence index and grid refinery processes. The experiments were measured during the four seasons to investigate the temperatures of water, glass, ambient, water production and solar intensity. The results show that the maximum daily water production of the designed still is 2.2 L/m2 in 17th of July with a low cost of 15 US dollars. The numerical model is predicted the thermal behavior of triangle, pyramid and pentagon types of solar stills. The results also show that the efficiency of the designed still is significantly improved to 60% compared with other experimental solar stills. The results also demonstrate that the manufacturing and transferring of the portable solar still during 20 years has a reasonable effect on the environment in terms of air acidification and water eutrophication.

A Confidence-Guided Technique for Tracking Time-Varying Features

Application scientists often employ feature tracking algorithms to capture the temporal evolution of various features in their simulation data. However, as the complexity of the scientific features is increasing with the advanced simulation modeling techniques, quantification of reliability of the feature tracking algorithms is becoming important. One of the desired requirements for any robust feature tracking algorithm is to estimate its confidence during each tracking step so that the results obtained can be interpreted without any ambiguity. To address this, we develop a confidence-guided feature tracking algorithm that allows reliable tracking of user-selected features and presents the tracking dynamics using a graph-based visualization along with the spatial visualization of the tracked feature. The efficacy of the proposed method is demonstrated by applying it to two scientific datasets containing different types of time-varying features.

A Simulation Model for a Hybrid-Electric Craft in Restricted Waters

Sustainable mobility is one of the most challenging issues for passenger transport inside environmental protected areas and ecologically fragile environments. To reduce the pollutant emissions, the adoption of electric or hybrid-electric solutions for crafts propulsion is a suitable option for green navigation. However, the operation in restricted basin leads also to specific critical issues for the vessel sailing, as dealing with shallow or restricted waters and transit under low air-gap bridges. The combination of these constraints with the adoption of a hybrid-electric propulsion system increases the design difficulties also for a small craft, requiring the use of advanced simulation models to assess the vessel performances. This work presents a simulation model for a small passenger craft that will operate in the Grado Lagoon. The model combines the hydrodynamic issues of manoeuvring and propulsion in restricted water with the simulation of the electric loads and capacity of the energy storage system installed onboard. The simulations performed with the developed simulation system are in accordance with data measured during trials on a prototype of the vessel. The developed model is a powerful tool for designers in order to rapidly assess the green capabilities of new projects since the early design stages.

The hot summer-cold winter region in China: Challenges in the low carbon adaptation of residential slab buildings to enhance comfort

The UK-China research project Low carbon climate-responsive Heating and Cooling of Cities (LoHCool) investigates enhanced indoor summer comfort in the 9 Billion m2 of building stock of the challenging Hot Summer and Cold Winter (HSCW) zone of China. The HSCW region lies South of the Huai River-Qin Mountain line below which central heating and cooling are deemed 'not required'. If this central government direction is relaxed, a significant carbon penalty could arise if the existing building stock is sealed and air conditioned to Western standards. LoHCool investigates the alternative strategy of increasing the existing stock's resilience to climate through low energy, low technology adaptation. The approach is applied here to typical slab building forms in Hangzhou and Chongqing in the East and West of the HSCW zone. Internal thermal conditions are simulated using the dynamic thermal model EnergyPlus calibrated using field data. Insofar as ventilation is a critical component of the adaptation schemes proposed, the local wind environment of the case study buildings is simulated using an advanced large eddy simulation model, Fluidity. Out of these diagnostic analyses, adaptation schemes are configured, specified and modelled, and found to significantly increase comfort with viable payback periods although supplementary cooling will be required as the century advances.

Measurement and analysis of cold spray residual stress using arbitrary Lagrangian–Eulerian method

Cold spray (CS) residual stress was measured by the X-ray diffraction (XRD) and contour methods. The residual stress components SX and SY, perpendicular to the thickness, have similar distributions and approximately equal magnitudes. Both are compressive on the deposited surface and become tensile inside the structure. An advanced simulation model based on the arbitrary Lagrangian–Eulerian (ALE) method was developed to investigate the residual stress distributions in a single CS microparticle and multi-layer CS microparticles and reveal the formation mechanism. The residual stress components SX and SY predicted by the proposed simulation model have the same distribution as shown by the measurements, i.e., compressive on the surface and tensile inside. As the number of deposition layers increases, the position of maximum tensile stress moves from the substrate to the deposited layers. The residual stress component SZ in the direction of the deposition thickness shows alternate tensile and compressive distributions in the transverse direction, which is quite different from that of the transverse component. The formation of CS residual stress is mainly affected by three aspects: the collisions among microparticles, the interactions between microparticles in the same layer, and interactions between microparticles in different layers. The present work provides a guideline for effectively tailoring the residual stress in CS parts and thereby improving the fatigue lifetime.