Simulation Results Research Articles

We have studied the photodissociation of gas-phase bromocyclopropane by 200nm wavelength ultraviolet radiation using ultrafast electron diffraction. Bromocyclopropane is a prototypical molecule in the study of organobromides, a class of molecules that have a significant impact on atmospheric ozone depletion through their photochemistry. Previous studies have revealed two possible reaction pathways for the photodissociation of bromine from bromocyclopropane; either the C-Br bond dissociates, leaving behind a cyclopropyl ring, or there is a concerted opening of the cyclopropyl ring along with the C-Br bond dissociation. In this work, both our experimental and simulation results indicate that the majority of the UV-photoexcited BCP molecules (88% ± 11% in the experiment) follow the first reaction pathway, in which the cyclopropyl ring remains closed after homolytic C-Br bond cleavage. This direct bond dissociation occurs within the experimental time resolution of 270fs. In order to differentiate between the possible reaction end-products, both of which have diffraction signals dominated by the bromine atom, a new analysis method has been employed, which is more sensitive to the structure of the end-products.

Phosphine (PH3) is an important functional material that plays a pivotal role in semiconductor fields. As semiconductor technology rapidly advances toward smaller sizes and higher performance, the requirements for the purity of phosphine in chip manufacturing are becoming increasingly stringent. To address this, this study has designed a purification process for ultra-high purity phosphine, capable of achieving a purity level of 6N (99.9999%) for phosphine products. The process was simulated and analyzed using Aspen Plus to investigate the influence of various factors on the purity of phosphine products. In this design, the sensitivity analysis function was used to determine the optimal number of theoretical stages, feed stage, and reflux ratios for each rectifying column in the process. It was also found that an increase in rectifying column pressure is detrimental to the removal of low-boiling-point substances such as N2 and O2 from phosphine. Furthermore, a double-effect distillation process was designed. After adopting the double-effect distillation process, the heat duty on all condensers and reboilers would decrease by 27%, but the purity of the phosphine product would decrease from 99.999943% to 99.999936%. Finally, a control scheme was designed for the distillation column used to extract phosphine products, and the control effect was dynamically simulated and tested using Aspen Plus Dynamics. The test results showed that disturbances caused by a decrease in feed were much more difficult to control than those caused by an increase in feed, and that low-boiling-point impurities had a much greater impact on the purity of phosphine products than high-boiling-point impurities. In addition, the results of steady-state simulation indicate that CO2 in phosphine is difficult to remove through distillation processes. Adding adsorption processes or membrane separation processes after distillation to remove CO2 from phosphine is a research direction for improving the purity of phosphine.

To investigate how rigid head motion interacts with 3D MRI k-space sampling strategies and to introduce motion-sampling plots as a framework for predicting motion artifacts. We evaluated a range of motion-sampling combinations across three sampling trajectories (Cartesian, stack-of-stars, kooshball) in both simulation and in vivo. Experiments included shifting motion states in k-space, changing the direction of motion with regards to the sampling, and varying the magnitude of motion. In vivo experiments were conducted on healthy volunteers mimicking patient motion while wearing a real-time pose-tracking device. Motion-sampling plots were used to map motion states directly onto k-space and assess their relationship to artifact appearance. Nine categories of motion artifacts were identified. The severity and nature of artifacts were found to depend heavily on the k-space distribution of motion states. Motion-sampling plots were seen to work as guides in predicting artifact appearance. In vivo findings supported simulation results. Artifacts were especially pronounced when motion discontinuities occurred near the center of k-space or aligned with slow phase-encoding directions. Motion-sampling plots offer an effective way to visualize and interpret motion artifacts in 3D MRI, providing insight beyond traditional motion-time plots. This framework enables systematic evaluation of motion robustness and can guide the development and validation of motion correction techniques. We propose practical recommendations for motion experiment design to improve reproducibility and benchmarking in MRI research.

Combining random forest and XGBoost models for source apportionment and health risk assessments of heavy metals in suburban farmland soils.

High-performance tracking control for the hydraulic manipulator should address the challenges of the uncertainties and unknowns associated with the electro-hydraulic servo system (EHSS). This paper presents an extended state observer-based chattering-free terminal sliding-mode (ESO-CFTSM) control scheme for hydraulic manipulators. A third-order integral chain model is developed to characterize the system dynamics, where uncertainties and unknowns are considered as disturbances and estimated by the ESO. Meanwhile, a full-order TSM manifold is designed to stabilize the closed-loop system in finite-time. For this proposed scheme, the feedforward compensation of disturbances is introduced in the equivalent control law. Furthermore, the composite reaching law and a low-pass filter are used to realize the chattering-free control. The singularity is avoided because there are no derivatives of terms with fractional powers in the control law. The stability of the overall system is proved by Lyapunov technique. The simulations using the physical model of a hydraulic manipulator with coupled dynamics show the effectiveness of the proposed scheme for trajectory tracking problems. Simulation results indicate that the proposed ESO-CFTSM can achieve superior performance without being affected by lumped disturbances.

The primary objective of deep learning is to have good performance on a large dataset. However, when the model lacks sufficient data, it becomes a challenge to achieve high accuracy in predicting these unfamiliar classes. In fact, the real-world dataset often introduces new classes, and some types of data are difficult to collect or simulate, such as medical images. A subset of machine learning is meta learning, or "learning-to-learn", which can tackle these problems. In this paper, a few-shot classification model is proposed to classify three types of brain cancer: Glioma brain cancer, Meningioma brain cancer, and brain Tumor cancer. To achieve this, we employ an episodic meta-training paradigm that integrates the model-agnostic meta-learning (MAML) framework with a prototypical network (ProtoNet) to train the model. In detail, ProtoNet focuses on learning a metric space by computing distances to class prototypes of each class, while MAML concentrates on finding the optimal initialization parameters for the model to enable the model to learn quickly on a few labeled samples. In addition, we compute and report the average accuracy for the baseline and our methods to assess the quality of the prediction confidence. Simulation results indicate that our proposed approach substantially surpasses the performance of the baseline ResNet18 model, achieving an average accuracy improvement from 46.33% to 92.08% across different few-shot settings. These findings highlight the potential of combining metric-based and optimization-based meta-learning techniques to improve diagnostic support in healthcare applications.

Abstract While bars are commonly observed in disk galaxies, the precise conditions governing their formation remain incompletely understood. To investigate these conditions, we perform a suite of N -body simulations of bulgeless disk galaxies with stellar masses in the range 10 9 ≤ M d ≤ 10 11 M ⊙ . Our galaxy models are constructed based on the observed properties of nearby barred galaxies from the S 4 G survey, and we systematically vary the halo scale radius to isolate its dynamical influence. Bars in our simulations form via repeated swing amplifications of disk perturbations, sustained by feedback loops. The amplification factor Γ depends on both the Toomre stability parameter Q T and the dimensionless wavelength X . Based on our simulation results, we propose a two-parameter bar formation criterion, Q T + 0.4( X − 1.4) 2 ≤ 1.8, corresponding to Γ = 10, which better captures the onset of bar formation than traditional one-parameter conditions. Bars in low-mass galaxies tend to be shorter and weaker, and are more susceptible to disruption by outer spiral arms. In contrast, bars in high-mass galaxies are longer, stronger, and more resilient to spiral interference. Bars in low-mass galaxies undergo only slight vertical thickening over time, whereas those in high-mass galaxies thicken rapidly via buckling instability.

Abstract As a newly emerging pillar industry in the medical field, telemedicine relies on the Internet and other transmission networks to complete the transmission of patient information and obtain the consultation results of telemedicine experts, which greatly improves the guarantee of patients’ lives. At the same time, the secure transmission of medical data is also one of the important standards of telemedicine, because any attack or theft caused by the loss of small details, changes, or information leakage will lead to the direction of treatment, resulting in serious consequences. Therefore, a new digital watermarking scheme for medical images is proposed in this paper, which combines image encryption and watermarking protection techniques. In the watermarking aspect, the Canny operator is used to obtain the self-embedding watermark image which is highly related to the plaintext, and the watermark embedding is realized by NSCT(Nonsubsampled Contourlet Transform), DWT(Discrete Wavelet Transform) transform, Fourier transform, and other operations. An efficient S-Box is constructed by using the generated chaotic sequence and the improved Z-transform, which fully disrupts the arrangement position of image pixels, and uses two-way diffusion to complete the distribution of plaintext information in ciphertext to realize image encryption. Simulation results and related tests show that the algorithm can successfully encrypt color and grayscale medical images, and has good robustness and ability to resist various external attacks.

A collaborative control strategy combining the hyperbolic sine-cosine optimization (SCHO) algorithm with fuzzy adaptive linear active disturbance rejection control is proposed to address the nonlinearity and uncertainties in the hydraulic position servo system of shock absorber test benches. First, based on the dynamic characteristics of the shock absorber fatigue test bench and the tested shock absorber, a linearized model of the valve-controlled hydraulic cylinder and its load was established. The coupling mechanism of system parameter perturbation and disturbance was also analyzed. A third-order LADRC (Linear Active Disturbance Rejection Control) was designed considering the linear model characteristics of the test bench hydraulic servo system model to quickly estimate internal system disturbances and perform real-time compensation. Secondly, a multi-objective optimization function was constructed by integrating system performance indicators and incorporating controller and observer bandwidths into the optimization objectives. The SCHO algorithm was used for the global search and optimization of key LADRC parameters. To enhance the controller’s adaptive capability of modeling uncertainties and external disturbances, a fuzzy adaptive module was introduced to adjust control gains online according to errors and their rates of change, further improving system robustness and dynamic performance. The results show that compared with traditional PID, under different working conditions, the proposed method reduced the maximum tracking error, overshoot, and system response time by an average of 45%, from 15% to 5%, and by approximately 30%, respectively. Meanwhile, the parameter combination obtained via SCHO effectively avoids the limitations of manual parameter tuning, significantly improving control accuracy and energy utilization. The simulation results indicate that this method can significantly enhance position-tracking accuracy compared with traditional LADRC, providing an effective solution for position-tracking control in hydraulic servo testing systems.

The article presents a comparison between the pressure conditions of a real low-pressure gas network and the results of hydraulic calculations obtained using various simulation programs and empirical equations. The calculations were performed using specialized gas network analysis software: STANET (ver 10.0.26), SimNet SSGas 7, and SONET. Additionally, the simulation results were compared with calculations based on the empirical Darcy–Weisbach and Renouard equations. In the first part of the analysis, two calculation models were compared. In one model, the geodetic elevation of individual network nodes was included (elevation-aware model), while in the second, calculations were performed without considering node elevation (flat model). For low-pressure gas networks, accounting for elevation is critical due to the presence of the pressure recovery phenomenon, which does not occur in medium- and high-pressure networks. Furthermore, considering the growing need to increase the share of renewable energy, the study also examined the network’s operating conditions when using natural gas–hydrogen mixtures. The following hydrogen concentrations were considered: 2.5%, 5.0%, 10.0%, 20.0%, and 50.0%. The results confirm the importance of incorporating elevation data in the modeling of low-pressure gas networks. This is supported by the small differences between calculated results and actual pressure measurements taken from the operating network. Moreover, increasing the hydrogen content in the mixture intensifies the pressure recovery effect. The hydraulic results obtained using different computational tools were consistent and showed only minor discrepancies.

This study integrates silico multiscale modeling─including quantum mechanical (QM) and molecular dynamics (MD) simulations─with experimental in vitro validation to comprehensively evaluate the pH-responsive drug delivery behavior of CeBTC-functionalized carbon nanotube (CNT) nanocarriers for sodium lignosulfonate (SLS). Among pristine (PCNT), moderately functionalized (MFCNT), and densely functionalized CNTs (DFCNT), the 20S-5CeBTC-DFCNT system emerged as the most efficient platform. Density functional theory (DFT) analysis revealed low HOMO-LUMO gaps (SLS: 0.206 eV; CeO2: 0.231 eV), supporting electronic reactivity and interaction compatibility. MD simulations demonstrated superior conformational stability for DFCNT with RMSD = 3.51 ± 0.33 Å, Rg = 16.28 ± 0.14 Å, RMSF = 1.17 ± 0.85 Å, and maximal solvent exposure (SASA = 9367.73 ± 182.07 Å2; PSA = 4147.67 ± 145.04 Å2). Drug loading interaction energy peaked at 5668.23 ± 54 kcal/mol, with Coulombic contribution of 3851.53 ± 53.36 kcal/mol. Upon pH 5.0-triggered protonation, drug (SLS) release energy reached 23616.87 ± 125 kcal/mol and the center-of-mass separation between SLS and carrier increased to 43.22 ± 6.32 Å, indicating efficient release. Notably, in vitro assays along with FE-SEM, HR-TEM, and FTIR confirmed 88% drug loading and 87.5% release over 100 h under acidic conditions, aligning closely with simulation results (100% loading, 95% release). In contrast, other nanocarriers (MFCNT and PCNT) showed lower performance, with higher RMSD (>25 Å), reduced PSA (<2200 Å2), weaker interaction energies (<4300 kcal/mol), and incomplete drug displacement (<31 Å). The release kinetics of DFCNT followed the Korsmeyer-Peppas model at pH 5.0 (R2 = 0.98193), confirming its pH-sensitive behavior. These findings establish DFCNT as a stable, tunable, and efficient nanocarrier for targeted drug delivery in acidic pathological environments, with promising potential for future redox-responsive and combination therapies.

Abstract Understanding the preseismic behavior of faults before large earthquakes is crucial. Previous quasistatic and quasidynamic modeling of nucleation with rate- and state-dependent friction (RSF) has reported diverse preseismic creep behaviors depending on the choice of a state-evolution law. However, a dynamic earthquake cycle simulation (ECS), which yields a more realistic solution, exhibits different results. Thus far, preseismic behavior in the dynamic ECS has been examined only for the aging law (AG). In this study, we investigated it for a linear RSF fault embedded in a two-dimensional linearly elastic infinite medium using a series of state-evolution laws. With AG and the Nagata law (NGT), the preseismic moment rate $$\text{d}M/\text{d}t$$ d M / d t was inversely proportional to the time-to-failure $${t}_{\text{f}}$$ t f in the final stage of nucleation, where the acceleration of a compact patch occurred. In contrast, the modified slip law (MSL) exhibited an approximately $${t}_{\text{f}}^{-0.9}$$ t f - 0.9 acceleration. The measure of uniformity of the slip rate distribution $${V}_{\text{ave}}/{V}_{\text{max}}$$ V ave / V max decreased before the final stage in all cases. Subsequently, AG and NGT showed a nearly constant $${V}_{\text{ave}}/{V}_{\text{max}}$$ V ave / V max , whereas $${V}_{\text{ave}}/{V}_{\text{max}}$$ V ave / V max kept decreasing for MSL. The transition in the acceleration and localization behavior with AG and NGT can be explained by the decrease in similarity to the slip law and convergence to the constant-weakening limit. The creep front for AG migrated deeper into the seismogenic patch with acceleration. For NGT and MSL, the migration behavior is influenced by the occasional switchback of the slow rupture, where said front propagates backward from the creep front. This switchback caused a longer creeping region at the onset of the earthquake. The critical crack length derived from the energy criterion approximated the simulated nucleation size well regardless of the occurrence of switchback. The differences and similarities between the simulation results and foreshock activities before large earthquakes were discussed. Graphical Abstract

Abstract. Iceberg observations in the Barents Sea are scarce. Numerical simulations of iceberg drift and deterioration help fill this gap. The quality of these simulation results depends, among other factors, on the accuracy of the environmental data (e.g., wind, waves, currents, salinity, temperature), often derived from ocean, sea ice and atmosphere models. In this study, we conduct a numerical experiment simulating the drift and deterioration of a large number of synthetic icebergs. We force the iceberg model with two atmospheric reanalyses (ERA5, CARRA) and two ocean and sea ice models (Topaz, Barents-2.5) in the Barents Sea for the years 2010–2014 and 2020–2021. The differences in iceberg model output are statistically quantified, illustrated using an exemplary trajectory, and explained based on variations in environmental input. We conclude that simulation results of iceberg drift and deterioration are highly sensitive to the choice of the environmental input, depending on the simulation goal, time frame, area of interest and input characteristics. Iceberg simulations using input from Barents-2.5 yielded a distinct regional distribution of iceberg density, 8 d longer drift duration, and −6.2 × 104 kg lower deterioration trend. These differences are primarily attributed to lower sea surface temperature (−0.41 °C), higher ice concentration (4 %), larger exposure to sea ice (23 %), larger water speeds (0.05 m s−1) and the representation of tides and topographically-steered currents in Barents-2.5, compared to Topaz. Atmospheric input has little impact on most iceberg characteristics. However, the iceberg pathways and their southern extent remain largely insensitive to variations in environmental inputs.

Abstract In multi-pass and multi-layer laser cladding, significant thermal accumulation occurs in the clad layers. This thermal accumulation causes substantial fluctuations in the molten pool's temperature field. It also induces significant variations in the flow field. Consequently, these changes affect the microstructure, formation quality, and mechanical properties of the clad layer. This study develops a finite element model that integrates heat transfer, fluid flow, and free surface dynamics to simulate the multi-layer deposition of IN718 alloy onto a 45 steel substrate. The model reveals the dynamic evolution of the temperature and flow fields under the influence of thermal accumulation during multi-layer deposition. Numerical results demonstrate that interlayer thermal accumulation exerts a more substantial influence than multi-pass overlapping. A continuous decrease in temperature gradient is observed throughout the entire process. After the first pass, the gradient measures 1.53×10⁶ K/m. It then declines sharply during interlayer deposition. The gradient ultimately reaches 8.5×10⁵ K/m by the end of cladding. This represents a total reduction of 44.4%. The molten pool flow velocity exhibits an initial increase from 0.42 m/s to 0.45 m/s, followed by a decrease and eventual stabilization at 0.37 m/s. With progressive deposition, insufficient edge support leads to increasingly severe gravity-driven pool inclination, particularly evident in the final pass of each layer. The average error between the temperature measurements and the simulation results is 4.42%. Furthermore, the simulated pool morphology aligns closely with experimental cross-sections, confirming the model's reliability.

Anapole mode, as a radiation-suppressed state, stems from the interaction of electric and toroidal dipoles, with its physical mechanism manifesting as destructive interference in far-field radiation and localized enhancement of near-field energy. In this work, we have proposed a flexible metasurface based on graphene-assembled film (GAF). Through subwavelength structural design of GAF, an anapole mode supported by a deformable substrate is realized in the microwave frequency band, overcoming the limitations of conventional rigid substrates. The simulation results have demonstrated that the metasurface maintains a highly stable resonance spectrum across incident angles ranging from −10° to 10°, with the excited anapole mode exhibiting robustness to angular variations, thereby preserving the localized enhancement of near-field energy. The close agreement between experimental results and electromagnetic simulation results confirms the feasibility of the proposed design. This metasurface features radiation-suppressed characteristics and flexibility, providing a research foundation for exploring mechanically deformable radiation-suppressed metasurfaces and simultaneously offering a new approach for the application of anapole metamaterials in fields such as biosensing and spectroscopy.

Abstract This paper offers an approach to deal with parametrized nonlinear strongly coupled thermo-poroelasticity problems. The approach uses the LATIN-PGD method and extends previous work in multiphysics problems. Proper Generalized Decomposition (PGD) allows the building of independent reduced-order bases for each physics. This point is particularly appropriate for thermo-poroelasticity problems whose physics present different dynamics. In parametrized problems dealing with material variability, a new computation is initialized with the result of a previous simulation to speed up the computation times. As a first step, the solver is validated on a standard benchmark in thermo-poroelasticity. The solver shows good performance even in the nonlinear frame. Then, the approach for parametrized problems is addressed on an academic problem and a more complex one, which is part of an industrial process. The results show that the method is effective and less time-consuming than naive approaches.

Abstract To address the issues of traditional spraying robots, such as heavy weight and limited adaptability to complex environments, a cable-driven continuum spraying robot (CDCSR) with pulley-winding flexible joints (PWFJ) is proposed, leveraging the high flexibility and compliance of continuum robots. The overall structure of the robot with transition joints and a stiffness-enhanced flexible joint are designed. The kinematic analysis of the CDCSR is conducted, and the mapping relationships among its configuration space, workspace, and actuation space are established. Additionally, a preliminary stiffness analysis of the flexible joint was performed based on the kinematic analysis and force conditions. Finite element analysis of a single flexible joint is carried out. Subsequently, simulation analysis is conducted on the workspace and kinematic mapping of continuum robots with one or two bending joints, followed by result comparison. A prototype of the robot is constructed, and bending performance tests, joint bending stiffness tests as well as spraying experiments in obstacle environments are conducted. Simulation and experimental results validated that the CDCSR exhibits higher joint stiffness (compared to conventional continuum mechanisms), superior motion performance and environmental adaptability.

Considering the rock creep effect can effectively improve the prediction accuracy of surface subsidence in goafs, which is particularly important for determining construction timing and ensuring the safe operation of surface structures. On basis of the time-dependent deformation characteristics of the overlying strata in mining areas, a nonlinear viscoelastic‒plastic (NVEP) model for accurately describing the three-stage creep behavior of rocks was established. The three-dimensional creep constitutive equations of this model were derived, and a secondary development of the creep model was implemented on the FLAC3D numerical simulation platform. A creep parameter inversion method for overlying strata in goaf areas was proposed by combining creep simulation analysis with a genetic algorithm. A specific project was selected as a case study, and the creep model and its related parameters were subsequently used to predict the long-term surface settlement behavior, providing a scientific basis for determining the appropriate construction timing for the surface railway in the goaf area of the region. The numerical simulation results indicate that the surface subsidence exhibits an exponential decay trend, which can be divided into three distinct stages: an initial rapid settlement phase (0-2 years), a transitional phase (2-3 years), and a long-term stabilization phase (beyond 4 years). On the basis of the railway construction specifications and the results of the numerical simulation analysis, the feasibility of constructing a railway on the goaf surface is assessed. The findings indicate that railway construction above the goaf in this area should be postponed for at least five years after the cessation of mining activities.

The escalating electromagnetic pollution from electronic devices necessitates high-performance microwave absorbers. Herein, we fabricate lightweight carbon nanotube (CNT)/reduced graphene oxide (rGO) porous composites via graphene oxide (GO)-mediated reconstruction of melamine-derived microspheres. Multiple characterizations (SEM, XRD, Raman, and Brunauer–Emmett–Teller) confirm that rGO can manipulate disordered CNT aggregates into interconnected 3D scaffolds with regular nanopores and enhance graphitic ordering. Electromagnetic analysis (2–18 GHz) indicates that incorporating rGO increases the dielectric loss tangent and facilitates optimal impedance matching. Consequently, the CNT/rGO-composite exhibits exceptional absorption capabilities: −40 dB reflection loss at 8 GHz (3.0 mm thickness) and a 4 GHz effective bandwidth (RL ≤ −10 dB) at 2 mm. Radar cross section simulations further demonstrate that the composite contained rGO with a maximum attenuation of 21.2 dBsm at 8 GHz, validating radar stealth performance. Such a high electromagnetic wave absorption performance is attributed to the synergetic effects of long-range propagation paths from internal multiple reflections, additional polarization centers due to heterogeneous interfaces, and other effects. Experimental and simulation results provide insights into the composite manufacturing of one-dimensional carbon nanotubes and two-dimensional reduced graphene oxide.

Abstract This study outlines the design, testing, and optimization of a soft actuator featuring variable stiffness based on the principle of chain mail jamming. The variable stiffness actuator was designed for a wearable exosuit for spinal rehabilitation. It enables the exosuit to apply and adjust varying forces in response to muscle activity, allowing for adaptive support during therapy. The jamming effect occurs when negative pressure is applied on the edges of a soft cover, causing particles inside to entangle. Finite Element Analysis (FEA) was conducted to evaluate the performance of the variable stiffness element in terms of the elastic bending modulus E at different particle parameters, such as length and diameter. Then, Response Surface Methodology (RSM) was applied to analyze the change of parameters and optimize them to get the optimal performance samples, which showed an improvement in stiffness and reduction in weight. Then, we manufactured the optimized sample using 3D printing to validate the simulation results. An experimental setup was used to conduct a three-point bending test, allowing an analysis of the actuator under different pressures. Finally, we customized, fabricated, and tested a wearable exosuit using the optimized variable stiffness element and compared it with the standard exosuit with fixed stiffness support.