Correct Simulation Research Articles

Calibration of an elastoplastic model of sand liquefaction using the swarm intelligence with a multi-objective function

According to post-seismic observations, spectacular examples of engineering failures can be ascribed to the occurrence of sand liquefaction, where a sandy soil stratum could undergo a transient loss of shear strength and even behave as a “liquid”. Therefore, correct simulation of liquefaction response has become a challenging issue in geotechnical engineering field. In advanced elastoplastic models of sand liquefaction, certain fitting parameters have a remarkable effect on the computed results. However, the identification of these parameters, based on the experimental data, is usually intractable and sometimes follows a subjective trial-and-error procedure. For this, this paper presented a novel calibration methodology based on an optimization algorithm (particle swarm optimization (PSO)) for an advanced elastoplastic constitutive model. A multi-objective function was designed to adjust the global quality for both monotonic and cyclic triaxial simulations. To overcome computational problem probably appearing in simulation of the cyclic triaxial test, two interrupt mechanisms were designed to prevent the particles from wasting time in searching the unreasonable space of candidate solutions. The Dafalias model has been used as an example to demonstrate the main programme. With the calibrated parameters for the HN31 sand, the computed results were highly consistent with the laboratory experiments (including monotonic triaxial tests under different confining pressures and cyclic triaxial tests in two loading modes). Finally, an extension example is given for Ottawa sand F65, suggesting that the proposed platform is versatile and can be easily customized to meet different practical needs.

Introduction to “Realistic Simulation of real CT systems with a basic-qualified Simulation Software - CTSimU2“

The lack of traceability to meter of X-ray Computed Tomography (CT) measurements still hinders a more extensive acceptance of CT in coordinate metrology and industry. To ensure traceable, reliable, and accurate measurements, the determination of the task-specific measurement uncertainty is necessary. The German guideline VDI/VDE 2630 part 2.1 [1] describes a procedure to determine the measurement uncertainty for CT experimentally by conducting several repeated measurements with a calibrated test specimen. However, this experimental procedure is cost and effort intensive. Therefore, the simulation of dimensional measurement tasks conducted with X-ray computed tomography can close these drawbacks. Additionally, recent developments towards a resource and cost-efficient production (“smart factory”) motivate the need for a corresponding numerical model of a CT system (“digital twin”) as well. As there is no standardized procedure to determine the measurement uncertainty of a CT system by simulation at the moment, the project series CTSimU was initiated, aiming at this gap. Concretely, the goal is the development of a procedure to determine the measurement uncertainty numerically by radiographic simulation. The first project (2019-2022), "Radiographic Computed Tomography Simulation for Measurement Uncertainty Evaluation - CTSimU" developed a framework to qualify a radiographic simulation software concerning the correct simulation of physical laws and functionalities [2-6]. The most important outcome was a draft for a new guideline VDI/VDE 2630 part 2.2, which is currently under discussion in the VDI/VDE committee. The follow-up project CTSimU2 "Realistic Simulation of real CT systems with a basic-qualified Simulation Software" will deal with building and characterizing a digital replica of a specific real-world CT system. The two main targets of this project will be a toolbox including methods and procedures to configure a realistic CT system simulation and to develop tests to check if this replica is sufficient enough. The result will be a draft for a follow-up VDI/VDE guideline proposing standardized procedures to determine a CT system's corresponding characteristics and test the simulation (copy) of a real-world CT system which we call a "digital twin".

Learning Invariance Preserving Moment Closure Model for Boltzmann–BGK Equation

As one of the main governing equations in kinetic theory, the Boltzmann equation is widely utilized in aerospace, microscopic flow, etc. Its high-resolution simulation is crucial in these related areas. However, due to the high dimensionality of the Boltzmann equation, high-resolution simulations are often difficult to achieve numerically. The moment method which was first proposed in Grad (Commun Pure Appl Math 2(4):331–407, 1949) is among the popular numerical methods to achieve efficient high-resolution simulations. We can derive the governing equations in the moment method by taking moments on both sides of the Boltzmann equation, which effectively reduces the dimensionality of the problem. However, one of the main challenges is that it leads to an unclosed moment system, and closure is needed to obtain a closed moment system. It is truly an art in designing closures for moment systems and has been a significant research field in kinetic theory. Other than the traditional human designs of closures, the machine learning-based approach has attracted much attention lately in Han et al. (Proc Natl Acad Sci USA 116(44):21983–21991, 2019) and Huang et al. (J Non-Equilib Thermodyn 46(4):355–370, 2021). In this work, we propose a machine learning-based method to derive a moment closure model for the Boltzmann–BGK equation. In particular, the closure relation is approximated by a carefully designed deep neural network that possesses desirable physical invariances, i.e., the Galilean invariance, reflecting invariance, and scaling invariance, inherited from the original Boltzmann–BGK equation and playing an important role in the correct simulation of the Boltzmann equation. Numerical simulations on the 1D–1D examples including the smooth and discontinuous initial condition problems, Sod shock tube problem, the shock structure problems, and the 1D–3D examples including the smooth and discontinuous problems demonstrate satisfactory numerical performances of the proposed invariance preserving neural closure method.

Impact of initial conditions and gas dynamics on the evaporation of a sessile droplet in microgravity and on-ground explained by a numerical model

The wide interest in the evaporation dynamics of sessile droplets has led to many studies aiming at understanding specific phenomena and overall behaviour. The effect of controlling the initial conditions, or the lack thereof, has not been studied extensively. One of the main issues are the conditions under which the droplet is injected on the substrate. This problem does not only raise questions on an experimental basis but also for numerical predictions. In the context of preparatory work for future space experiments in a sounding rocket and on board the International Space Station, initial conditions are difficult to control and their complete understanding lacks, whereas simulations may shed light on the subject. This work develops a comprehensive axisymmetric transient model that describes the injection of a sessile droplet evaporating into a gas phase as well as the evaporation process of that droplet. The model is validated against experimental data in both Earth and microgravity conditions. The amount of injected volume has been shown to increase the evaporation rate, with a weaker influence at microgravity with respect to Earth conditions. Comparing our model to the case where no injection history is present reveals that neglecting the latter has no significant influence on the evaporation dynamics nor on the simulated velocity and temperature profiles. This suggests that in most cases it is not necessary to include the injection period, so that uncertainties involving the injection are not an obstacle to model the evaporation of sessile droplets. Moreover, it also appears that thermal supply by the injected fluid plays a large role during injection in suppressing Marangoni convection, whilst the latter becomes the main mechanism determining the flow patterns after the injection. Finally, it appears that for high-molar-mass vapours the gas dynamics play an important role in the evaporation process. In particular, for correct numerical simulations, it is necessary to consider concentration-dependent gas properties, and especially concentration-dependent gas density, these effects being most often neglected in other approaches, which results in underestimated evaporation rates.

Modeling criteria for the seismic assessment of existing masonry buildings

Masonry elements modeling criteria and capacity models are useful for a correct numerical simulation. At first, this work refers to the piers and spandrels strength models according to the Italian design code, investigated in a dimensionless form. Then, the paper presents some preliminary results referring to the masonry strength and in-plane floor flexibility influence on the masonry buildings seismic behavior. Nonlinear pushover analyses are conducted on an ideal existing masonry case study, having three floors and assuming three specific masonry strengths and three floor behaviors. The pushover analyses, performed according to the equivalent frame model, show that in the case of poor masonry the response is not influenced by the in-plane floor stiffness, while it affects the response in the case of masonry of good quality. A mixed global failure mechanism is observed in all analyses performed.

Shadowing effects in the diffractive scattering of virtual photons on nuclei and its interference with the process of bremsstrahlung

In cosmic ray physics and high-energy neutrino astronomy, muons are ubiquitous. Due to their slow energy loss and consequently large range at high energies, the correct simulation of their transport through matter is especially important for underground experiments. The dominant energy loss processes are ionization and at higher energies pair production, bremsstrahlung and inelastic interaction with nuclei. A muon energy loss process, which has hitherto been neglected in such simulations, is the diffractive scattering of virtual photons on nuclei. As the elastic channel of this process has the same final state as the bremsstrahlung process (mu + A rightarrow mu + A + gamma ), an interference term arises, whose sign depends on the charge of the lepton. It is found that the contribution of this process was overestimated in earlier works and is significantly affected by shadowing.

Comparative Analysis of Numerical Methods for Simulating N-Heptane Combustion with Steam Additive

Currently, thermal power plants operating on hydrocarbon fuels (gas, fuel oil, peat, shale, etc.) are one of the main sources of electricity. An effective and promising method for suppressing harmful emissions (NOx, carbon oxides, soot) from the combustion of fossil fuels is the injection of steam into the combustion chamber. The influence of various mathematical submodels was studied on the accuracy of the numerical simulation of the process of n-heptane combustion in a laboratory burner with steam additive to the reaction zone as a promising chemical engineering method for the disposal of substandard liquid fuels and combustible waste with the production of thermal energy. The problem was solved in a three-dimensional stationary formulation. Systematic verification of these submodels, and a comparison of the results of the calculation with the experimental data obtained were carried out. The comparison with the experimental data was carried out for gas components and temperature distribution at the burner outlet; high agreement of the results was achieved. Optimal submodels of the methodology for calculating the process of fuel combustion in a jet of steam were determined. The best agreement with the experiment data was obtained using the EDC model in combination with a mechanism consisting of 60 components and 305 elementary reactions. More correct simulation results were obtained using the RSM turbulence model and the DO radiation model.

A Review on Atmospheric Dispersion System for Air Pollutants Integrated with GIS in Urban Environment

The objective of this article is to present comprehensive findings and analysis of studies performed on air pollutant dispersion in urban environments. It captures India’s rising environmental pollution due to urbanization, industrialization, and population growth. Dispersion of pollutants due to the wind in the lower Atmospheric Boundary Layer (ABL) is a major concern nowadays. The dispersion field around the buildings is a critical parameter to analyze and it primarily depends on the correct simulation of the wind flow structure. Therefore, studies performed on this in past years are being reviewed. Additionally, a brief review of different air dispersion models that are integrated with the Geographic Information System (GIS) has been studied in this article to assess the exposure. The results of these studies provide the urban air dispersion model aligning to three sub-models i.e., Emission, Weather Prediction, and Dispersion models. Various factors like wind speed, wind direction, cloud cover, traffic emission, disposal of waste, transportation, and others are considered. This study also captures the problems and risks being faced while creating a model, and its possible mitigation approaches.

A correlated sampling-based Monte Carlo simulation for fast CBCT iterative scatter correction.

In recent years, cone-beam computed tomography (CBCT) has played an important role in medical imaging. However, the applications of CBCT are limited due to the severe scatter contamination. Conventional Monte Carlo (MC) simulation can provide accurate scatter estimation for scatter correction, but the expensive computational cost has always been the bottleneck of MC method in clinical application. In this work, an MC simulation method combined with a variance reduction technique called correlated sampling is proposed for fast iterative scatter correction. Correlated sampling exploits correlation between similar simulation systems to reduce the variance of interest quantities. Specifically, conventional MC simulation is first performed on the scatter-contaminated CBCT to generate the initial scatter signal. In the subsequent correction iterations, scatter estimation is then updated by applying correlated MC sampling to the latest corrected CBCT images by reusing the random number sequences of the task-related photons in conventional MC. Afterward, the corrected projections obtained by subtracting the scatter estimation from raw projections are utilized for FDK reconstruction. These steps are repeated until an adequate scatter correction is obtained. The performance of the proposed framework is evaluated by the accuracy of the scatter estimation, the quality of corrected CBCT images and efficiency. Overall, the difference in mean absolute percentage error between scatter estimation with and without correlated sampling is 0.25% for full-fan case and 0.34% for half-fan case, respectively. In simulation studies, scatter artifacts are substantially eliminated, where the mean absolute error value is reduced from 15 to 2HU in full-fan case and from 53 to 13HU in half-fan case. Scatter-to-primary ratio is reduced to 0.02 for full-fan and 0.04 for half-fan, respectively. In phantom study, the contrast-to-noise ratio (CNR) is increased by a factor of 1.63, and the contrast is increased by a factor of 1.77. As for clinical studies, the CNR is improved by 11% and 14% for half-fan and full-fan, respectively. The contrast after correction is increased by 19% for half-fan and 44% for full-fan. Furthermore, root mean square error is also effectively reduced, especially from 78 to 4HU for full-fan. Experimental results demonstrate that the figure of merit is improved between 23 and 43 folds when using correlated sampling. The proposed method takes less than 25s for the whole iterative scatter correction process. The proposed correlated sampling-based MC simulation method can achieve fast and accurate scatter correction for CBCT, making it suitable for real-time clinical use.

GPU-Accelerated All-Atom Particle-Mesh Ewald Continuous Constant pH Molecular Dynamics in Amber.

Constant pH molecular dynamics (MD) simulations sample protonation states on the fly according to the conformational environment and user specified pH conditions; however, the current accuracy is limited due to the use of implicit-solvent models or a hybrid solvent scheme. Here, we report the first GPU-accelerated implementation, parametrization, and validation of the all-atom continuous constant pH MD (CpHMD) method with particle-mesh Ewald (PME) electrostatics in the Amber22 pmemd.cuda engine. The titration parameters for Asp, Glu, His, Cys, and Lys were derived for the CHARMM c22 and Amber ff14sb and ff19sb force fields. We then evaluated the PME-CpHMD method using the asynchronous pH replica-exchange titration simulations with the c22 force field for six benchmark proteins, including BBL, hen egg white lysozyme (HEWL), staphylococcal nuclease (SNase), thioredoxin, ribonuclease A (RNaseA), and human muscle creatine kinase (HMCK). The root-mean-square deviation from the experimental pKa's of Asp, Glu, His, and Cys is 0.76 pH units, and the Pearson's correlation coefficient for the pKa shifts with respect to model values is 0.80. We demonstrated that a finite-size correction or much enlarged simulation box size can remove a systematic error of the calculated pKa's and improve agreement with experiment. Importantly, the simulations captured the relevant biology in several challenging cases, e.g., the titration order of the catalytic dyad Glu35/Asp52 in HEWL and the coupled residues Asp19/Asp21 in SNase, the large pKa upshift of the deeply buried catalytic Asp26 in thioredoxin, and the large pKa downshift of the deeply buried catalytic Cys283 in HMCK. We anticipate that PME-CpHMD will offer proper pH control to improve the accuracies of MD simulations and enable mechanistic studies of proton-coupled dynamical processes that are ubiquitous in biology but remain poorly understood due to the lack of experimental tools and limitation of current MD simulations.

Effect of the Length and Pressure of a Gas Jet on Optical Harmonics Generation by 4.5-μm Femtosecond Laser Radiation of a Fe:ZnSe Laser System

The effect of the length and pressure of an argon gas jet on low-order harmonics (5th, 7th, 9th, and 11th) generation by 4.5-μm femtosecond laser radiation of a Fe:ZnSe laser system has been studied experimentally. It has been shown that an increase in the length of the generation medium up to the waist length allows one to increase the generation efficiency by a factor of 12. It has also been demonstrated that a change in the length of the gas medium changes the pressure dependence of the energy of the generated radiation because of change in the phase matching conditions, whose correct simulation requires the inclusion of nonlinear propagation effects for pump pulse and generated harmonics.

Coupling of an SPH-based solver with a multiphysics library

A two-way coupling between the Smoothed Particle Hydrodynamics-based (SPH) code with a multiphysics library to solve complex fluid-solid interaction problems is proposed. This work provides full access to the package for the use of this coupling by releasing the source code, completed with guidelines for its compilation and utilization, and self-contained template setups for practical uses of the novel implemented features, is provided here. The presented coupling expands the applicability of two different solvers allowing to simulate fluids, multibody systems, collisions with frictional contacts using either non-smooth contact (NSC) or smooth contact (SMC) methods, all integrated under the same framework. The fluid solver is the open-source code DualSPHysics, highly optimised for simulating free-surface phenomena and structure interactions, uniquely positioned as a general-purpose Computational Fluid Dynamics (CFD) software with a GPU-accelerated solver. Mechanical systems that comprise collision detection and/or multibody dynamics are solved by the multiphysics library Project Chrono, which uses a Discrete Element Method (DEM). Therefore, this SPH-DEM coupling approach can manage interactions between fluid and complex multibody systems with relative constraints, springs, or mechanical joints. Program summaryProgram title: DualSPHysics-ChronoCPC Library link to program files:https://doi.org/10.17632/g2cc37dw4f.1Licensing provisions: DualSPHysics and DSPHChronoLib under GNU Lesser General Public License (LGPL); Project Chrono under BSD-3-Clause License.Programming language: C++ and CUDANature of problem: The simulation of turbulent free-surface flows in interaction with complex fixed or floating structures is essential to address typical marine and coastal engineering problems. The Smoothed Particle Hydrodynamics (SPH) method is particularly suitable for solving this type of nonlinear problems. However, this type of application usually requires mechanical restrictions between the different structural elements (spherical joints, hinges, or springs), as well as the correct simulation of collisions between solid objects. In these cases, it is necessary to combine the SPH method with other numerical methods that allow performing these multiphysics simulations.Solution method: DualSPHysics-Chrono is a two-way coupling between an SPH solver and a multiphysics library that combines fluid simulation using a Lagrangian approximation and interactions between solids using Discrete Element Method (DEM). DualSPHysics solver is a GPU-optimized implementation of the SPH method that allows efficient simulation of fluid-structure interaction problems. Whereas Project Chrono is a DEM implementation for simulating multibody dynamics that includes collision detection and numerous mechanical constraints to solve complex mechanisms. The coupling of DualSPHysics and Project Chrono combines the capabilities of both models under a free software framework.Additional comments including restrictions and unusual features: The SPH solver includes a version implemented with CUDA (Compute Unified Device Architecture) to exploit the parallelism of NVIDIA graphics processing units (GPUs).

Validation of finite element connection modeling by comparison of experimental and virtual power injection methods

There are several ways to obtain the matrix of damping loss factors and coupling loss factors for Statistical Energy Analysis. The most recent approach is Virtual SEA, where the Power Injection Method is performed virtually on a finite element model. In order to validate this approach, the most common connection types are investigated in this paper through an L-junction of two coupled steel plates. Virtual SEA and experimental Power Injection Method results are compared in a bent, line welded, superglued and spotwelded variants. The respective finite element connection representation is also validated during the comparison. It was found that with the correct simulation setup, Virtual SEA provides good agreement with the experimental results. In case of the spotwelded variants, further investigations were necessary regarding the parameters of the connection. The influence of these parameters was evaluated and the greatest source of deviations in the results is found.

Effect of Increased Interprofessional Familiarity on Team Performance, Communication, and Psychological Safety on Inpatient Medical Teams

In large academic centers, medical residents work on multiple clinical floors with transient interactions with nursing colleagues. Although teamwork is critical in delivering high-quality medical care, little research has evaluated the effect of interprofessional familiarity on inpatient team performance. To determine the effectiveness of increased familiarity between medical residents and nurses on team performance, psychological safety, and communication. A 12-month randomized clinical trial in an inpatient general medical service at a large academic medical center was completed from June 25, 2019, to June 24, 2020. Participants included 33 postgraduate year (PGY)-1 residents in an internal medicine residency program and 91 general medicine nurses. Fifteen PGY-1 residents were randomized to complete all 16 weeks of their general medicine inpatient time on 1 medical nursing floor (intervention group with 43 nurses). Eighteen PGY-1 residents completed 16 weeks on 4 different general medical floors as per usual care (control group with 48 nurses). The primary outcome was an assessment of team performance in physician-nurse simulation scenarios completed at 6 and 12 months. Interprofessional communication was assessed via a time-motion study of both work rounds and individual resident clinical work. Psychological safety and teamwork culture were assessed via surveys of both residents and nurses at multiple time points. Of the intervention and control PGY-1 residents, 8 of 15 (54%) and 8 of 18 (44%) were women, respectively. Of the nurses in the intervention and control groups with information available, 37 of 40 (93%) and 34 of 38 (90%) were women, respectively, and more than 70% had less than 10 years of clinical experience. There was no difference in overall team performance during the first simulation. At the 12-month simulation, the intervention teams received a higher mean overall score in leadership and management (mean [SD], 2.47 [0.53] vs 2.17 [0.39]; P = .045, Cohen d = 0.65) and on individually rated items were more likely to work as 1 unit (100% vs 62%; P = .003), negotiate with the patient (61% vs 10%; P = .001), support other team members (61% vs 24%; P = .02), and communicate as a team (56% vs 19%; P = .02). The intervention teams were more successful in achieving the correct simulation case outcome of negotiating a specific insulin dose with the patient (67% vs 14%; P = .001). Time-motion analysis noted intervention teams were more likely to have a nurse present on work rounds (47% vs 28%; P = .03). At 6 months, nurses in the intervention group were more likely to report their relationship with PGY-1 residents to be excellent to outstanding (74% vs 40%; P = .003), feel that the input of all clinical practitioners was valued (95% vs 53%; P < .001), and say that feedback between practitioners was delivered in a way to promote positive interactions (90% vs 60%; P = .003). These differences diminished at the 12-month survey. In this randomized clinical trial, increased familiarity between nurses and residents promoted more rapid improvement of nursing perception of team relationships and, over time, led to higher team performance on complex cognitive tasks in medical simulations. Medical centers should consider team familiarity as a potential metric to improve physician-nursing teamwork and patient care. ClinicalTrials.gov Identifier: NCT05213117.

Operando Raman spectroelectrochemical study of polyaniline degradation: A joint experimental and theoretical analysis

Operando Raman spectroscopy of an electrode composed of the polyaniline is performed to elucidate the fundamental polarization mechanism occurring in an electrochemical supercapacitor during a large electroactive voltage window. The polyaniline presented two distinct redox processes; the first is associated with converting the leucoemeraldine base to the emeraldine and then with the conversion of emeraldine to the pernigraniline. By operando Raman spectroscopy, the exchange of the head-to-tail polarization mechanism by forming head-to-head coupling during voltammetric was verified. In the charging process, oxidized polyaniline forms polaron and bipolaron structures, causing deprotonation, while sulfate from the electrolyte inserting in the polyaniline chain causing a balance of the electronic charge. The materials modeling was shown to analyze the effects of the applied high potential and its correlation with the p-doping/dedoping sulfate anion and water molecules in the polyaniline chain. The density functional theory using van der Wall correction (DFT + vdW) simulation elucidated tensile stress with the insertion of sulfate anion and water molecules. It was not observed any hydrogen bond between polyaniline chain and sulfate anion, which facilitate and contribute to the conductivity of polyaniline emeraldine-like structure.

Relationship Between Talofibular Impingement and Increased Talar Tilt in Incongruent Varus Ankle Osteoarthritis

Category: Ankle; Ankle Arthritis Introduction/Purpose: Recently, talofibular bony impingement has been postulated to be a source of ankle pain. This study aimed to evaluate the relationship between talofibular impingement and increased talar tilt in incongruent varus ankle OA patients using bilateral weightbearing CT. Methods: Incongruent varus ankle osteoarthritis was defined as a talar tilt of more than 4° on standard ankle anteroposterior radiographs. We retrospectively reviewed 30 patients with unilateral incongruent varus ankle osteoarthritis with normal alignment of the contralateral ankle. All patients underwent bilateral weightbearing computed tomography and standing plain radiographs. The talar tilt and the distance between the talar lateral process and lateral malleolar tip were measured from a standing ankle anteroposterior radiograph of both sides. Talar and fibular spurs were assessed on the coronal and axial views of weightbearing computed tomography. After simulating the correction of the talar tilt in varus ankle osteoarthritis, talofibular bony impingement was reassessed. Results: On the varus side, the distance between the talar lateral process and the lateral malleolar tip was significantly shorter than that on the contralateral side (p &lt; .001). Talar spur was present in the varus side of all 30 patients on the axial view of weightbearing computed tomography and in the control side of 10 patients. After the simulation of talar tilt correction, talofibular impingement (overlap) occurred in all 30 patients with a larger extent in the severe talar tilt subgroup (p &lt; .001). Conclusion: Talofibular impingement by lateral gutter osteophytes is closely related to increased talar tilt in patients with incongruent varus ankle osteoarthritis. Therefore, lateral gutter osteophytes should be resected to stabilize mortise and improve clinical outcomes.

P‐3.25: Synergistic effects between Optical Proximity Correction (OPC) and lithography process simulation in display backplane

In this paper, lithographic simulation tools, including Optical Proximity Correction (OPC), have been applied in designing backplane layout of displays. That will lead to better resolution of lower feature size of the lithography process in display manufacturing with wider process window.

Seismic velocity field estimation using sonic well logs decomposed by Singular Spectrum Analysis (SSA) and Exponentially Weighted Moving Average (EWMA) - A case of study in Recôncavo Basin, Brazil

The determination of an accurate seismic wavefield velocity propagating in the subsurface is a problem faced currently by geoscientists. However, velocity analysis on land seismic data is often compromised due to lack of a good signal-to-noise ratio, absence of guide reflectors, and low fold, which significantly affects the quality of the final velocity model and, consequently, the seismic image. This paper introduces an improvement in the root mean square (RMS) velocity model obtained from the Polo-Miranga seismic cube, located in the Recôncavo sedimentary basin in northeast of Brazil, using slowness well log data. The available vagarosity logs were smoothed using the Exponentially Weighted Moving Average (EWMA) and Singular Spectrum Analysis (SSA) to determine a new measurement that reflects the low frequency of the p-wave seismic velocity to be employed in the velocity analysis. Estimating the best parameter of the EWMA algorithm required some tests to smooth the slowness. At the same time, the first component of the sonic decomposition into three other curves was a reasonable way to estimate the velocity. Those techniques showed robust results and enhanced some reflectors in the 3D stack. Furthermore, the proposed methodology’s performance is validated through the normal moveout correction (NMO) simulation and on the time-slice image.

Zero-shot sim-to-real transfer of reinforcement learning framework for robotics manipulation with demonstration and force feedback

AbstractIn the field of robot reinforcement learning (RL), the reality gap has always been a problem that restricts the robustness and generalization of algorithms. We propose Simulation Twin (SimTwin) : a deep RL framework that can help directly transfer the model from simulation to reality without any real-world training. SimTwin consists of a RL module and an adaptive correct module. We train the policy using the soft actor-critic algorithm only in a simulator with demonstration and domain randomization. In the adaptive correct module, we design and train a neural network to simulate the human error correction process using force feedback. Subsequently, we combine the above two modules through digital twin to control real-world robots, correct simulator parameters by comparing the difference between simulator and reality automatically, and then generalize the correct action through the trained policy network without additional training. We demonstrate the proposed method in an open cabinet task; the experiments show that our framework can reduce the reality gap without any real-world training.

Fast and Accurate Computation of the Displacement Force of Stent Grafts after Endovascular Aneurysm Repair.

Purpose: Currently, the displacement force of stent grafts is generally obtained using computational fluid dynamics (CFD), which requires professional CFD knowledge to perform the correct simulation. This study proposes a fast, simple, and clinician-friendly approach to calculating the patient-specific displacement force after endovascular aneurysm repair (EVAR). Methods: Twenty patient-specific post-EVAR computed tomography angiography images were used to reconstruct the patient-specific three-dimensional models, then the displacement forces were calculated using CFD and the proposed approaches, respectively, and their numerical differences were compared and analyzed. Results: Based on the derivation and simplification of the momentum theorem, the patient-specific displacement forces were obtained using the information of the patient-specific pressure, cross-sectional area, and angulation of the two stent graft ends, and the average relative error was no greater than 1.37% when compared to the displacement forces calculated by CFD. In addition, the linear regression analysis also showed good agreement between the displacement force values calculated by the new approach and CFD (R = 0.999). Conclusions: The proposed approach can quickly and accurately calculate the patient-specific displacement force on a stent graft and can therefore help clinicians quickly evaluate the post-EVAR displacement force.