Internal Structural Parameters Research Articles

Optimization design of a two-step microreactor with spiral structure for high-performance catalytic reactions

Abstract In order to enhance the efficiency of diphenyldimethoxysilane preparation in microreactors, this study utilized the computational fluid dynamics simulation based on the finite element method to explore the impact of the internal structural parameters of the spiral two-step microreactor (STMR) on the reaction outcomes, with the aim of optimizing its structure for high-performance catalytic reactions. By designing a microreactor based on the Archimedean spiral shape and introducing two ribbed obstacles, the structure was optimized through adjusting the relevant ratios. The effects of different-sized structures and obstacles within the reaction zone and non-reaction zone on the product concentration and reaction results were discussed. The results demonstrate that lower obstacle heights and smaller aspect ratios (P = 2:7, R = 5:6) are beneficial for improving the reaction efficiency and product concentration. This study offers a theoretical foundation for microreactor design and is anticipated to further drive the development of microreactor technology.

Research the lubrication characteristics on the modified main thrust roller of the slewing bearings

The load capacity and lubrication performance of the slewing bearing are fairly sensitive to edge effects at both ends of the main thrust rollers. Therefore, quantitative investigations of the edge effect at both ends of slewing bearing is practically important. In this study, an elastic fluid lubrication model of the slewing bearing that considered the external load and internal structural parameters is established. A modification function of rollers is included in a finite long-line contact elastic fluid lubrication model to perform the dynamic analysis. The simulated oil film’s thickness and pressure distributions are compared under different working conditions. And the edge effect is eliminated by modifying the rollers’ construction. The results indicate that under the large eccentric load, the speed of the slewing bearing must be decreased to ensure elastic fluid lubrication performance. A genetic algorithm that used to discover the optimal modification length shows the best busbar of the main thrust roller is 12 μm, which could decrease the vibration amplitude of the unmodified roller by 8.13%. This result gives a significant way for slewing bearing’s structural design.

Optimisation of properties of Ti3SiC2 reinforced copper matrix composites

Cu-Ti3SiC2 composites were prepared by solid-liquid mixing, mechanical alloying and discharge plasma sintering. The composites' internal structure and performance characteristics were characterized using OM, SEM, XRD, TEM, conductivity and mechanical tests. The interaction of Ti3SiC2 with the Cu matrix was systematically investigated. The formation of Cu5Si, Cu15Si4 and TiC particles was found to optimize the bonding of Ti3SiC2 with the copper matrix. Also, the effect of different Ti3SiC2 contents (0.5, 1, 2 and 3 wt%) on the materials' internal structure and performance parameters was investigated. The results showed that the samples of Cu-1 wt% Ti3SiC2 exhibit excellent overall performance. It achieved a yield strength of 270.4 MPa, a tensile strength of 295.2 MPa, an elongation rate of 23.8 %, an electrical conductivity of 85.8 % (IACS), a coefficient of friction of 0.465, and a wear rate of 7.8×10−5 mm3N−1m−1.

Reconstruction of infrared absorption and scattering coefficient distributions of semitransparent medium using Adam algorithm combined with adjoint model

Precise reconstruction of infrared optical coefficient distributions within semitransparent medium holds great significance in engineering field. This study introduces the Adam algorithm to reconstruct the infrared absorption and scattering coefficient distributions of a 2D semitransparent slab. The discrete ordinate method (DOM) is utilized to solve the time-domain radiative transfer equation (TD-RTE), and the radiative intensity at boundary is employed as input signal. The gradient calculation of the objective function employs the adjoint equation method (AEM). Results demonstrate that the adaptive moment estimation (Adam) algorithm can simultaneously estimate the infrared absorption and scattering coefficient distributions with high accuracy. Compared to traditional optimization methods, the Adam algorithm demonstrates significant superiority in terms of reconstruction accuracy, computational efficiency, and tolerance to measurement errors. Furthermore, it is also appropriate for determining the infrared optical parameters of different internal structures. Balancing both calculation accuracy and computation time, a recommended learning rate of η = 50 is suggested for the reconstruction task. The Adam algorithm presents limitations for reconstructing the distributions in scattering-dominant medium. The normalized root-mean-square errors of the absorption and scattering coefficients respectively increase to 0.2311 and 0.0655 when the standard measurement error is increased to 20 %.

Structure Design of Pressure Swirl Atomizing Nozzle

Based on Solidworks and Fluent, the inner flow field of swirl nozzle is modeled and simulated. The simulation results of the internal flow field of the nozzle show that the change of the internal structural parameters of the nozzle has an importa nt impact on the flow characteristics of the working medium at the outlet of the nozzle. The parameters such as the axial velocity, tangential velocity and atomization angle at the outlet of the nozzle under different structural parameters are comprehensively compared, and finally the nozzle structure with the optimal atomization effect is determined.

Forward modeling of quake’s infrasound recorded in the stratosphere on board balloon platforms

Acoustic waves generated by seismic waves contain information on the internal structure of planets, and can be sensed by pressure sensors onboard high-altitude balloons. To identify the various contributions (infrasound signal, noise, balloon response, etc.) in such pressure records, a full waveform modeling is implemented and completed by infrasound ray tracing and additional data analysis. Here, we analyze the Stratéole-2 pressure data associated with two earthquakes (Garcia et al. Geophys. Res. Lett. 49(15):e98844, 2022) and compared these to full waveform simulations by SPECFEM2D-DG-LNS software. Even if our simulations do not precisely reproduce the waveform observed in the frequency range [0.05, 0.3] Hz, we show that the waveform presents more sensitivity to quake and internal structure parameters than to atmospheric structure, and that seismic surface wave dispersion is observed in balloon pressure records. The long-duration pressure oscillations observed after the main infrasonic signal cannot be fully reproduced by our one-dimensional input model even when source time function complexity and aftershocks are considered. These features are ascribed mainly to the complex vertical ground movements below the balloon and partly to late secondary infrasound arrivals excited by the interactions of seismic waves with the topography. These results enhance the advantages and limitations of quake-related infrasound observations on board terrestrial and planetary balloon platforms.Graphical

Experimental and theoretical investigation of a miniature simple pressure pulsation attenuator lined with porous polyurethane material

A miniature simple pressure pulsation attenuator (PPA) lined with porous polyurethane material is designed and a theorical model is established for analyzing the pressure pulsation attenuation performance of PPA. The effect of internal structural parameters of PPA and external operating conditions on attenuation performance is investigated theoretically and experimentally. Spectral intensity is used as a new method to evaluate the pressure pulsation attenuation, and other common index such as pressure pulsation rate and frequency spectrum are also compared in detail. The results show that spectral intensity can more accurately reflect the overall effect of pressure pulsation and the attenuation effect at a specific frequency. The present PPA is more suitable for low static pressure and can effectively eliminate low-frequency and high-frequency pressure pulsation. In addition, the diameter and number of pores can affect the pressure pulsation attenuation. Insertion loss of PPA exhibits multiple peaks, which are mainly influenced by liner length and liner material. Furthermore, the flow rate increases as the pulsation frequency increases for the piston pump based on frequency control, which can cause the pulsation attenuation performance to basically remain unchanged. The research offers valuable insights for the design, optimization, and analysis of PPA in seawater hydraulic system.

Pressure propagation mechanism of open-cell aluminium foam within a pipe under hypervelocity impact

Low-density open-cell aluminium (Al) foam exhibits a different deformation mode under hypervelocity impacts compared to being subjected to medium-low speed and quasi-static compression. In this case, material flows between cells in the form of metal jets and propagates forward. This paper establishes the open-cell Al foam model based on Voronoi tessellation. Using numerical methods, one-dimensional hypervelocity constant velocity impact experiments of 1–6 km/s inside a closed pipe are conducted on Al foam with different internal structure parameters (average cell diameter: 2–3.5 mm; ligament width: 0.251–1 mm). Propagation mechanism of pressure waves in foams and the key factors affecting the propagation velocity are investigated. Three zones are divided according to the condition of jet distribution along the impact direction: unaffected zone, jet influence zone, and particle accumulation zone. The variation of the length of different zones with impact velocity is discussed: higher velocities result in longer jet influence zones but shorter particle accumulation zones. Meanwhile, length of zones is closely related to the width of Al foam ligament and cell pore diameter: the larger the diameter of cell pores and the smaller the width of ligaments, the longer the length of the jet influence zone. Time dependence is exhibited in the length of jet influence zone for the large cell pore diameter specimens(≥0.03 cm). Particle pressures are extracted using the one-dimensional averaging method, which propagates forward significantly lower than in dense materials. Dominant factors affecting the pressure wave propagation of open-cell Al foam, i.e., the internal unloading space, are obtained by combining two-dimensional hypervelocity impact simulation experiments with different boundary conditions. A strong correlation between metal jet distribution and particle pressure propagation is observed.

Improved magnetic-based apparatus enables non-destructive and high sensitive steel-bar corrosion detection

Steel-bar corrosion can not only induce corrosion cracking, but also cause the bearing capacity decline of concrete structures. This contribution reported an improved magnetic-based steel bar corrosion detection apparatus with simple structure and high accuracy. Accelerated corrosion tests on steel rebar were carried out to calibrate the accuracy of the magnetic-based corrosion detection apparatus. A parameter of sensitivity coefficient, k, was proposed to evaluate the corrosion detection sensitivity of the apparatus. An equivalent numerical model was established based on multi-physical simulation to quantify the corrosion degrees and explore the impacts of the frame internal structural parameters. Results show that k is stable and changes linearly with the diameter of steel rods tested. Increasing frame width and foot length can increase k, and adding extra calibration magnetic circuits leads to reduction in k. Overall, the modified magnetic-based apparatus provides a simple, reliable, accurate and non-destructive method for steel corrosion detection.

Fabrication of controlled porous and ultrafast dissolution porous microneedles by organic-solvent-free ice templating method

Porous Microneedles (PMNs) have been widely used in drug delivery and medical diagnosis owing to their abundant interconnected pores. However, the mechanical strength, the use of organic solvent, and drug loading capacity have long been challenging. Herein, a novel strategy of PMNs fabrication based on the Ice Templating Method is proposed that is suitable for insoluble, soluble, and nanosystem drug loading. The preparation process simplifies the traditional microneedle preparation process with a shorter preparation time. It endows the highly tunable porous morphology, enhanced mechanical strength, and rapid dissolution performance. Micro-CT three-dimensional reconstruction was used to better quantify the internal structures of PMNs, and we further established the equivalent pore network model to statistically analyze the internal pore structure parameters of PMNs. In particular, the mechanical strength is mainly negatively correlated with the surface porosity, while the dissolution velocity is mainly positively correlated with the permeability coefficient by the correlation heatmap. The poorly water-soluble Asiatic acid was encapsulated in PMNs in nanostructured lipid carriers, showing prominent hypertrophic scar healing trends. This work offers a quick and easy way of preparation that may be used to expand PMNs function and be introduced in industrial manufacturing development.

Performance and regression analysis of air-cooled thermoelectric cooling system using response surface methodology and numerical simulation

In this study, the response surface methodology (RSM) combined with numerical simulation (NS) techniques is used to perform regression model of an air-cooled thermoelectric cooler (TEC) system. To obtain the interaction models between the thermal resistance (Rh) of the external hot-side heat sink and the internal structure parameters of the TEC (leg height, h; leg width, w; numbers of P/N leg pairs, N), regarding the key performance of the TEC. According to the NS and RMS results Imax, Qcmax, and Qh decline with the rise of Rh under different N, h, and w. The decline rate is rise with the elevation of N, the increase of the w, and the decrease of the h. COP and Tcmin decrease with an increase in h, while increase with an increase in w, N, and Rh. The key factors Rh, w, h and N in the air-cooled TEC system are studied using RSM. The second-order response models for the response variables (COP, Tcmin, Qcmax,Imax and dTmax) with respect to the influencing factors (Rh, w, h and N) are established using the Box-Behnkn Design (BBD) method in RSM.

On formation, annihilation, and evolution of potential wells, and nonlinear phenomena of multi-magnet energy sink system.

This paper investigates the formation, annihilation, and evolution mechanisms of potential energy wells in nonlinear energy sink systems. The nonlinear energy sink system is composed of multiple inner and outer magnets. Two multi-magnet energy sink (MES) architectures are designed: a single-magnet vibrator and a double-magnet vibrator. Multi-stable (bi-, tri-, quad-, penta-, hexa-, and hepta-stable) mechanisms are elaborated by the Poincaré section and bifurcation diagram concerning the magnet length, the link length, and the MES configuration. The results show that the change in the internal structural parameters of the MES system will generate different types of bifurcations (i.e., saddle-node, subcritical, and super pitchfork bifurcations) and phase trajectories and have rich nonlinear response behaviors in the low frequency and wide frequency range, which can be used for damping and vibration reduction of engineering structures, vibration control, and energy source of the microgrid.

FORMATION OF TWO-PHASE ZONES DURING INTERNAL OXIDATION OF BINARY ALLOYS

In the paper the formation patterns of two-phase regions during the internal oxidation process in low-alloyed binary alloys is studied. The goal of the research is the creation of a mathematical model for the internal oxidation process, which is to describe the kinetics of formation and evolution of internal oxidation zones, the study of the patterns governing the two-phase zone formation during internal oxidation, the study of the space-time dynamics of the structural parameters of the two-phase area, namely the number of the oxide particles, their average radius and the phase volume, at different stages of the internal oxidation zone evolution. The two-phase process of diffusion saturation with light components applied to binary alloys is analyzed theoretically. The conditions for formation of disperse oxide particles are formulated. A mathematical model for the formation of two-phase areas as well as the numerical solution for the system of equations describing the kinet- ics of formation and evolution of the two-phase area for different values of the process parameters is proposed. The modeling and experiments demonstrate that the distribution of structural parameters of the two-phase area has complex, non-monotonous nature. The influence of the main parameters of the process on the kinetics of the formation of the two-phase area in a lightly-alloyed binary nickel-based alloy plate is also determined. All stages of the plate’s oxidation process are studied – from the inception of the particles to the coalescence of second-stage particles. The results of the work could be used for developing new technologies in thermal and chemical-thermal treatments for disperse strengthening of materials using internal oxidation, as a physical basis for seeking ways of providing certain distributions of the internal oxidation zone structural parameters, which are required to give the al- loy a necessary set of physical and mechanical properties. The comparison of the modeling and experimental results shows a good correlation, which allows them to be recommended for developing new technologies in disperse strengthening, new heat-resistant steels, disperse-strengthened magnetic materials and electrotechnical alloys.

Low-fat microwaved peanut snacks production: Effect of defatting treatment on structural characteristics, texture, color, and nutrition

This study develops low-fat microwaved peanut snacks (LMPS) using partially defatted peanuts (PDP) with different defatting ratios, catering to people’s pursuit of healthy, low-fat cuisine. The effects of defatting treatment on the structural characteristics, texture, color, and nutrient composition of LMPS were comprehensively explored. The structural characteristics of LMPS were characterized using X-ray micro-computed tomography (Micro-CT) and scanning electron microscope (SEM). The results demonstrated that the porosity, pore number, pore volume, brightness, brittleness, protein content, and total sugar content of LMPS all significantly increased (P<0.05) with the increase in the defatting ratio. At the micro level, porous structure, cell wall rupture, and loss of intracellular material could be observed in LMPS after defatting treatments. LMPS made from PDP with a defatting ratio of 64.44% had the highest internal pore structural parameters (porosity 59%, pore number 85.3×105, pore volume 68.23 mm3), the brightest color (L* 78.39±0.39), the best brittleness (3.64±0.21) mm–1), and the best nutrition (high protein content, (34.02±0.38)%; high total sugar content, (17.45±0.59)%; low-fat content, (27.58±0.85)%). The study provides a theoretical basis for the quality improvement of LMPS.

Artificial neural network for deciphering the structural transformation of condensed ZnO by extended x-ray absorption fine structure spectroscopy

Pressure-induced structural phase transitions play a pivotal role in unlocking novel material functionalities and facilitating innovations in materials science. Nonetheless, unveiling the mechanisms of densification, which relies heavily on precise and comprehensive structural analysis, remains a challenge. Herein, we investigated the archetypal B4 → B1 phase transition pathway in ZnO by combining x-ray absorption fine structure (XAFS) spectroscopy with machine learning. Specifically, we developed an artificial neural network (NN) to decipher the extended-XAFS spectra by reconstructing the partial radial distribution functions of Zn–O/Zn pairs. This provided us with access to the evolution of the structural statistics for all the coordination shells in condensed ZnO, enabling us to accurately track the changes in the internal structural parameter u and the anharmonic effect. We observed a clear decrease in u and an increased anharmonicity near the onset of the B4 → B1 phase transition, indicating a preference for the iT phase as the intermediate state to initiate the phase transition that can arise from the softening of shear phonon modes. This study suggests that NN-based approach can facilitate a more comprehensive and efficient interpretation of XAFS under complex in-situ conditions, which paves the way for highly automated data processing pipelines for high-throughput and real-time characterizations in next-generation synchrotron photon sources.

Modeling and analysis of ice condensation on bridge deck pavement surface based on heat transfer theory and finite element method

Bridge surfaces usually freeze more easily than road surfaces in wet and cold conditions, which is unfavorable to traffic safety. This study aims to develop an ice prediction model for bridge deck pavement structures by integrating external climatic factors and internal structure parameters, and to analyze the mechanism of ice condensation. This model adopted finite element analysis to deal with the heat transfer problem and the latent heat during the phase change process. A series of experiments were designed to validate the model, and the relative difference was around 10 %. Results shown that: among external climatic factors, the impact of changes in water accumulation on ice formation is not significant. Meanwhile, the air temperature has the greatest impact, and there is a non-linear relationship between wind speed and the initial freezing time. In the study on the effect of aging, it was found that aged asphalt concrete pavement would freeze earlier and melt later compared to new. When comparing different structures, it was observed that the initial freezing time of the bridge deck pavement structure was 0.8 h earlier than the road structure, and the total freezing time was 2.8 h shorter than the road structure. It was also found that the lower thermal conductivity would delay the occurrence of icing when the bridge deck pavement structure was in a cooling stage. Finally, it was observed that the vehicle speed played a critical role in determining the direction of the heat flow with a specific value, and the value would increase as the temperature difference decreased. This prediction model is useful for transportation agencies to understand the mechanism of pavement ice formation and ensure traffic safety in winter.

Straintronics with single-layer MoS2 : A quantum Monte Carlo study

Using state-of-the-art quantum Monte Carlo (QMC) methods, we study straintronic properties of a single MoS2 monolayer. 2D MoS2 is a quintessential straintronic material for which many experiments have been performed. First, we determine the equilibrium atomic structure which is not known experimentally and is strictly needed to correctly determine the straintronic properties. That enables us to precisely analyze the quasiparticle band gaps for any applied biaxial strain, which we describe by a bivariate paraboloid function of lattice constant and internal structural parameter. Using the fixed-node QMC calculations fitted by analytical formulas, we localize the following excited state crossings between the direct, K→K, and indirect Γ→X and K→K/2 excitations. Based on this highly accurate many-body treatment, we predict a gauge factor of 136 meV/% for the K→K transition and a fairly narrow window of ≈2.8% from compressive to mildly tensile strains, accounting for only ≈0.3 eV band gap change maintaining the direct character of the gap. Consequently, we suggest that, compared to other 2D materials, such as phosphorene, there is only a limited straintronic tuneability in this material often studied for its straintronic properties. QMC results are compared to results of standard DFT modeling, which reveal insights into the corresponding inaccuracies and therefore open a window for educated use of rapid DFT approaches. Published by the American Physical Society 2024

Optimal shaping of acoustic black holes for sound absorption in air

This article presents a systematic numerical study of the absorbing properties of acoustic black holes (ABHs) serving as an anechoic termination of waveguides. The study focuses on the sensitivity of ABHs’ absorbing performance to their profile and internal-structure parameters. The article compares numerical predictions from 1D model based on the Riccati equation with a detailed 2D model based on the linearized Navier-Stokes equations and the finite element method, finding good agreement among all results, especially for ABHs with fine internal structures. The mean value of the reflection coefficient modulus is used to quantify the ABH’s absorbing performance, and the article introduces the use of power-law functions and cubic splines to define the ABH’s shape function. An evolutionary algorithm is employed to optimize the ABH’s profile, resulting in improved absorbing performance. The numerical results suggest that the optimum shape is simple and more-or-less insensitive to other geometrical and internal-structure parameters.

Preservation of strawberries using chitosan incorporated with lemongrass essential oil: An X-ray computed tomography analysis of the internal structure and quality parameters

Preservation of strawberries using chitosan incorporated with lemongrass essential oil: An X-ray computed tomography analysis of the internal structure and quality parameters

Micromechanics study of short carbon fiber-reinforced thermoplastics fabricated via 3D printing using design of experiments

In this study, short carbon fiber-reinforced thermoplastic (sCFRTP) was 3D-printed under different printing parameters, and the influence of the combination of printing parameters on the tensile properties and internal structure (void volume fraction, fiber orientation, and fiber length) of the 3D-printed sCFRTP was investigated through tensile testing, X-ray computed tomography, microscopic observations and theoretical analysis based on a micromechanics model (MM). A total of ten printings and characterizations were performed via the design of experiments, and the outcomes displayed specimens that were fabricated under optimal printing parameters (specimen DoE) exhibited a Young's modulus of 5.1 ± 0.3 GPa and a tensile strength of 73.3 ± 0.9 MPa, resulting in the highest Young's modulus and tensile strength. The MM analysis successfully reproduced the experimental stress-strain response as well as the equivalent stiffness of the sCFRTPs with a much shorter time than finite element analysis by inputting the measured fiber length, void volume fraction, and fiber orientation distribution into the in-house MM code. From this MM analysis, it was suggested the higher Young's modulus and tensile strength observed in the specimen DoE is due to more of the relatively long fibers are oriented in the print direction with fewer voids. Furthermore, the influence of internal structure parameters on the mechanical properties of the 3D-printed sCFRTPs was analyzed, revealing that fiber length has a greater impact on the mechanical properties than void volume fraction and fiber orientation distribution.