Internal Structure Research Articles

Study on the folding damage mechanism of SiC fiber braided fabric based on synchrotron radiation CT and finite-element analysis

Silicon carbide (SiC) fiber exhibits high strength, thermal resistance, and chemical stability, but its insufficient flexural strength renders it unsuitable for use in flexible structural materials. In this study, the microstructure evolution and damage mechanisms of SiC fiber braided fabric were investigated at different braiding angles and folding stages using synchrotron micro computed tomography (µ-CT) and finite-element analysis. Results from synchrotron radiation CT scans indicate that, with an increase in the number of folding cycles, both fiber surface fractures and slippage gradually increased, leading to a looser internal structure and diminished fiber continuity. The SiC fiber braided fabric at 37.8° was predominantly influenced by the folding behavior, exhibiting a higher frequency of fiber breakages. Conversely, the 43.1° SiC fiber braided fabric was primarily affected by inter-bundle abrasion, resulting in looser fiber bundles and increased slippage. In the case of the 41.2° SiC fiber braided fabric, under the combined effects of friction and folding, the highest occurrences of fiber slippage and breakages were observed. Finite-element simulation results reveal that the stress at the folding site of the 40° braided fabric was higher than those of the 45° and 50° braided fabrics, confirming the experimental conclusion that the folding resistance of SiC fiber fabrics is poorest at a braiding angle of around 41° to 42°. This research is of significant importance for a deeper understanding of the folding performance and damage behavior of SiC fiber braided fabric, providing valuable insights for further optimizing material design and applications.

INVESTIGATION OF FLUORINATED DOUBLE-WALL CARBON NANOTUBES

Experimental results of investigation of the original and fluorinated ultra-long double-walled carbon nanotubes (DWCNTs) with a length of at least 1000 μm are presented. The degree of fluoridation did not exceed 27 at.%. It has been shown that the process of fluorination of samples of double-walled carbon nanotubes deforms the outer surface of the nanotube wall although does not destroy its internal concentric structure, while the diameter of the fluorinated nanotube increases by 1.5-2 times. In addition, the fluorinated samples, which were thermochemically purified from iron particles and other forms of carbon before fluorination, demonstrated many split/cut ends of nanotubes. The effect of fluorination on the electrical properties of initial and purified samples of double-walled carbon nanotubes was studied. It was revealed that with an increase in temperature from 80 to 300 K for non-fluorinated and fluorinated purified nanotube samples, the resistivity decreases, which corresponds to the semiconductor nature of the conductivity. It was also revealed that when a sample of initial DWNT is fluorinated, a change in the nature of conductivity from semiconductor to metallic is observed. With an increase in temperature from 80 to 300 K, the resistance of the non-fluorinated sample of the original DWNTs decreased by 45%, while the resistance of the fluorinated sample increased by 11%. Despite the decrease in electrical conductivity as a result of fluorination of the purified samples, all samples remained conductors, which presumably indicates partial fluorination of the outer wall of the DWNTs while maintaining the structure of the inner wall. Thus, fluorination of double-walled carbon nanotubes with a well-aligned and concentric structure leads to the formation of fluorocarbon nanostructures, which can be promising materials for electronic nanodevices. For citation: Karaeva A.R., Khaskov M.A., Kurzhumbaev D.Zh., Kulnitskiy B.A., Mordkovich V.Z. Investigation of fluorinated double-wall carbon nanotubes. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 38-48. DOI: 10.6060/ivkkt.20246710.4y.

Compressive behaviors and deformation mechanism of carbon fiber reinforced epoxy composites: A microscopic and molecular dynamics perspective

AbstractInvestigating the macro‐mechanical properties of polymer composites at the nanoscale is a challenging topic. Here we report the compressive performances of carbon fiber‐reinforced epoxy composites using molecular dynamics (MD) simulations. The evolution of microstructure and microscopic energy, including free volume, radius of gyration, dihedral angle, potential energy, and interaction energy, has been investigated to characterize compressive behaviors at the nanoscale. Molecular chains gradually bend, and the movement space of the molecular chains decreases during compression loading. The radius of gyration and dihedral angle are deformed into a state of irreversible plasticity to accommodate the microstructural transformation. The interaction energy increases and subsequently declines as the carbon fiber/epoxy interface gets closer, reflecting the transition of the internal structure. The inhomogeneity and interfacial concentration distribution of stress, and local molecular stiffness under various strains have been obtained to reveal the nanoscopic mechanism of epoxy failure and interface delamination during compression. This study reveals the compression behaviors and deformation mechanism of carbon fiber‐reinforced epoxy composites at the molecular level, providing directions and possibilities for molecular design and structural optimization of composites.Highlights The nanoscopic compression deformation of CFRP composites is studied. Microstructural evolution and conformation transformation are revealed. The evolution and transition of microscopic energy are analyzed. Micro‐mechanism of epoxy deformation and interface delamination is elucidated.

Experimental and numerical investigation of the damage propagation in regularly arrayed short fiber reinforced composite laminates under low‐velocity impact

AbstractThe outstanding mechanical performance and flowability of unidirectionally arrayed chopped strands (UACSs) give them an advantage in the manufacture of engineering structures with complex geometry. For the application of practical structures, the impact responses and damage evolution of material under low‐velocity impact must be investigated in advance. In this study, UACS laminates and continuous carbon fiber laminates with a stacking sequence of [0/90]4s and a thickness of 2 mm were fabricated for low‐velocity impact tests at 7, 11, 15, and 20 J. The impact responses and postimpact intralaminar damage area were analyzed according to the experimental results, including impact load responses and ultrasound C‐scan inspections. Moreover, to predict the damage evolution of the internal structure, the 3D finite element models were constructed in ABAQUS using a progressive damage model (PDM) through a user‐material subroutine VUMAT. Compared with continuous carbon fiber laminates, the dissipated energy of UACS laminates increases by approximately 10.64% and 57.37% for the 15 and 20 J, respectively. However, the intralaminar damage area of UACS laminates decreased by 29.96% and 28.16% at 15 and 20 J, respectively, since the discontinuous slits in UACS laminates can guide damage paths and suppress damage propagation.Highlights The regularly arrayed short fiber reinforced composite was studied. Revealed the low‐velocity impact responses and predicted the damage evolution. UACS and CFRP laminates have comparable impact performance. Illustrated the slits design can suppress the damage to a relatively small area.

Analysis of errors in endodontic treatment according to cone-beam computed tomography

AIM. The aim of the study was to study the frequency of errors in endodontic treatment according to cone beam computed tomography.MATERIALS AND METHODS. 71 cone beam computed tomography (CBCT) scans of patients treated by random sampling who sought treatment and consultation in the period 2022–2023 were studied. 256 teeth previously subjected to endodontic treatment with the presence or absence of radiological signs of chronic apical periodontitis were examined. The assessment of the quality of root canal obturation and the features of the anatomical structure of teeth was carried out. The data of the «Ray RAYSCAN alpha 3D» cone beam computed tomograph were studied using the OnDemand3DDental program. The results were considered statistically significant at p< 0.05.RESULTS. In 57.42% of cases, there were no signs of periapical pathology, and in 42.58%, foci of bone destruction in the periapical region were observed. Homogeneously, 58.59% of root canals were sealed to the apex. In 16.79% of cases, the removal of filling material outside the root canal was noted. 10.54% of teeth with insufficient root canal filling depth and 6.64% of teeth with a missing root canal were also identified.CONCLUSIONS. There is a decrease in the incidence of the most common errors of endodontic treatment. The method of cone beam computed tomography is important at the stage of diagnosis and planning of endodontic treatment to assess the features of the internal structure of the tooth.

Ultrasonographic Assessment of Masseter and Anterior Temporal Muscle Thickness and Internal Structure in Young Adult Patients With Bruxism.

The current study is a comparative cross-sectional analysis study to determine the thickness and internal structure of the masseter muscle (MM) and anterior temporal muscle (ATM) in patients with bruxism by ultrasonography (USG). A total of 100 patients (36 males, 64 females), 50 with bruxism and 50 without bruxism, aged 20-30 years were included in the study. All patients were investigated with MM and ATM USG. The thickness of the muscles was measured at rest and during clenching and the internal structure at rest was classified as Type I, II, and III. Differences in the internal structure between bruxism and non-bruxism groups were determined using the Chi-square test (p < 0.05). The most common internal structure in bruxism was Type 2 in MM (74%) and Type 1 in ATM (46%), whereas in non-bruxism, Type 1 in MM (58%) and Type 1 in ATM (80%) were found most frequently. While there was a statistically significant difference in the internal echogenic pattern in the right MM and ATM in bruxism (p < 0.05), no significant difference was observed on the left side (p > 0.05). Bruxism patients had higher rest and clench thicknesses than non-bruxism patients on both sides in MM and ATM, however, this did not result in a statistically significant difference (p > 0.05). The results obtained showed that the evaluation of internal structure and thickness differences via USG is crucial in understanding the nature of the bruxism process affecting the masseter and ATM, facilitating its clinical diagnosis and leading to its treatment.

Effect of Surface Morphology and Internal Structure on the Tribological Behaviors of Snake Scales from Dinodon rufozonatum.

Snakes can move freely on land, in lakes, and in other environments. During movement, the scales are in long-term contact with the external environment, providing protection to the body. In this study, we evaluated the mechanical properties and scratching performance of the ventral and dorsal scales from Dinodon rufozonatum, a generalist species that moves on both land and in streams under wet and dry conditions. The results showed that the elastic modulus and hardness of the dry scales were greater than those of the wet scales. The average scale friction coefficient under wet conditions (0.1588) was 9.3% greater than that under dry conditions (0.1453). The scales exhibit brittle damage in dry environments, while in wet environments, ductile damage is observed. This adaptation mechanism allows the scales to protect the body by dissipating energy and reducing stress concentration, ensuring efficient locomotion and durability in both terrestrial and aquatic environments. Understanding how this biomaterial adapts to environmental changes can inspire the development of bionic materials.

Construction of Multiphase Concave Tetrahedral PdInMo Nanocatalyst for Enhanced Alcohol Oxidation

AbstractHeterogeneous palladium‐based catalysts show excellent catalytic properties for electrocatalytic oxidation of alcohols, but the construction of such heterogeneous catalysts is a challenge. Here, a multiphase tetrahedral PdInMo nanocatalyst is prepared by a one‐pot reaction method. And the multiphase tetrahedral PdInMo nanocatalyst consists of a face‐centered cubic structure and an intermetallic structure. Due to the oxygen affinity of indium and molybdenum atoms, the interface defects of internal multiphase structure, and intermetallic structure, the multiphase concave tetrahedral PdInMo nanocatalyst shows enhanced catalytic efficiency in the electrocatalytic oxidation reaction of methanol and ethanol. Compared with commercial Pd/C catalysts, PdIn0.117Mo0.037 nanocatalyst has the best mass activity and specific activity. In electrocatalysis of methanol oxidation, the mass activity (2205.57 mA mgPd−1) and specific activity (6.67 mA cm−2) are 4.81 and 3.40 times than that of a commercial Pd/C nanocatalyst (458.5 mA mgPd−1, 1.96 mA cm−2), respectively. In the electrocatalysis of ethanol oxidation, the mass activity (2668.49 mA mgPd−1) and specific activity (8.11 mA cm−2) are 4.06 and 3.14 times than that of the commercial Pd/C nanocatalyst (655.83 mA mgPd−1, 2.58 mA cm−2), respectively. This study provides a reference for the design of highly efficient palladium catalysts for alcohol oxidation.

Galois theory and homology in quasi-abelian functor categories

Given a finite category T, we consider the functor category AT, where A can be any quasi-abelian category. Examples of quasi-abelian categories are given by any abelian category but also by non-exact additive categories as the categories of torsion(-free) abelian groups, topological abelian groups, locally compact abelian groups, Banach spaces and Fréchet spaces. In this situation, the categories of various internal categorical structures in A, such as the categories of internal n-fold groupoids, are equivalent to functor categories AT for a suitable category T. For a replete full subcategory S of T, we define F to be the full subcategory of AT whose objects are given by the functors F:T→A with F(T)=0 for all T∉S. We prove that F is a torsion-free Birkhoff subcategory of AT. This allows us to study (higher) central extensions from categorical Galois theory in AT with respect to F and generalized Hopf formulae for homology.

Application of Different Image Processing Methods for Measuring Rock Fracture Structures under Various Confining Stresses

Fractures within granite may become channels for fluid flow and have a significant impact on the safety of waste storage. However, internal aperture variation under coupled conditions are usually difficult to grasp, and the inevitable differences between the measured data and the real fracture structure will lead to erroneous permeability predictions. In this study, two different CT (Computed Tomography) image processing methods are adopted to grasp internal fractures. Several CT images are extracted from different positions of a rock sample under different confining stresses. Two critical factors, i.e., aperture and the contact area ratio value within a single granite fracture sample, are investigated. Results show that aperture difference occurs under these two image processing methods. The contact area ratio value under two image processing methods has less than 1% difference without confining stress. However, there is larger than ten times difference when the confining stress increases to 3.0 MPa. Moreover, the edge detection method has the capability to obtain a relatively accurate internal fracture structure when confining pressure is applied to the rock sample. The analysis results provide a better approach to understanding practical rock fracture variations under various conditions.

Application of Soft Magnetic Composite in XEV Motor Core Manufacturing: Process Effects and Performance Analysis

This study explores the application of AncorLam HR (Höganäs, Sweden), a soft magnetic composite material, in the stator core of an axial flux permanent magnet drive motor. Building on previous research that provided mechanical and thermal properties of the material, the focus is on analyzing how the manufacturing process affects the motor core’s shape. A bulk prototype was created based on case 3, which demonstrated the least deviation in density and internal stress. The prototypes were produced under the conditions of SPM 7 and 90 °C, and a heat treatment in a nitrogen atmosphere for 1 h, resulting in an average density error of 0.54%, confirming process effectiveness. A microstructural analysis using scanning electron microscopy (SEM) on Sample 2, with the highest density, confirmed consistency between simulation and prototype trends. Electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analyses revealed that the internal phase structure remained unchanged. Energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) identified the elimination of phosphorus (P) during molding, affecting the insulating layer, a critical factor for SMC materials. In motor simulations and actual measurements, the average torque was recorded as 37.7 N·m and 34.7 N·m at 1500 rpm and 27.7 N·m and 25.1 N·m at 2000 rpm, respectively. The torque comparison observed in the actual measurements compared to the simulation results indicates that the output loss increases in the actual measurements due to the deterioration of the insulation performance judged based on the microstructure evaluation. This study confirms the viability of using AncorLam HR in motor cores for electric vehicles and provides key data for improving the performance.

Topology optimization and numerical validation for heat transfer improvement in a packed-bed reactor with monolithic catalyst

This study focuses on optimizing heat transfer in packed-bed reactors by simplifying the problem to a two-dimensional steady-state heat conduction scenario. The objective is to efficiently arrange a limited volume of high-conductivity material to transport heat from the source to the low-conductivity heat-absorbing materials, representing the reacting fluid phase. The topology optimization problem is tackled using a density-based method that relies on a gradient-based algorithm. The optimized design is extruded and compared to a honeycomb internal structure using high-fidelity simulations for steam methane reforming. Results show a 6.04 % improvement in CH4 conversion for the optimized structure, highlighting the potential of this method to enhance monolithic catalysts, particularly in cases where heat transfer critically influences the reaction.

Development and Validation of Dimensional Clinical Personality Inventory 2 (IDCP-2) Algorithms to Assess ICD-11 Personality Trait Domain Qualifiers.

With the advent of the new diagnostic model for personality disorders in the 11th revision of the International Classification of Diseases (ICD-11), researchers and practitioners in World Health Organization signatory countries are urged to implement it. This study aims to develop a brief, reliable, and valid scale for assessing maladaptive personality traits according to the ICD-11 model, using the item pool of the Dimensional Clinical Personality Inventory (IDCP-2). Quantitative and qualitative criteria for item selection were applied to a sample of 251 Brazilian adults. As a result, the 25 items (five items per factor) were selected, demonstrating promising evidence of validity based on the internal structure with a database of 1,659 Brazilian adults. In addition, we found good evidence of validity based on relationships with external variables, particularly those related to personality pathology, in a sample of 617 Brazilian adults. The implications of these findings are discussed.

Mixed-mode coupling in the red clum. I. Standard single star models

The investigation of global, resonant oscillation modes in red giant stars offers valuable insights into their internal structures. In this study, we investigate in detail the information we can recover on the structural properties of core-helium burning (CHeB) stars by examining how the coupling between gravity- and pressure-mode cavities depends on several stellar properties, including mass, chemical composition, and evolutionary state. Using the structure of models computed with the stellar evolution code we calculate the coupling coefficient implementing analytical expressions, which are appropriate for the strong coupling regime and the structure of the evanescent region in CHeB stars. Our analysis reveals a notable anti-correlation between the coupling coefficient and both the mass and metallicity of stars in the regime $M in agreement with data. We attribute this correlation primarily to variations in the density contrast between the stellar envelope and core. The strongest coupling is expected thus for red-horizontal branch stars, partially stripped stars, and stars in the higher-mass range exhibiting solar-like oscillations ($M While our investigation emphasises some limitations of current analytical expressions, it also presents promising avenues. The frequency dependence of the coupling coefficient emerges as a potential tool for reconstructing the detailed stratification of the evanescent region.

Thin-film freeze-drying of an influenza virus hemagglutinin mRNA vaccine in unilamellar lipid nanoparticles with blebs

Messenger RNA (mRNA) vaccines have revolutionized the fight against infectious diseases and are poised to transform other therapeutic areas. Lipid nanoparticles (LNP) represent the most successful delivery system for mRNA. While the mRNA-LNP products currently in clinics are stored as frozen suspensions, there is evidence that freeze-drying mRNA-LNP into dry powders can potentially enable their storage and handling at non-freezing temperatures. Previously, we successfully applied thin-film freeze-drying (TFFD) to transform a polyadenylic acid [poly(A)]-LNP formulation from a liquid suspension to dry powders. The poly(A)-LNP were structurally multilamellar spheres without blebs, but the mRNA vaccines in clinics are comprised of mRNA-LNP that are structurally spheres surrounded by a unilamellar lipid bilayer, with some containing blebs, and it was reported that the presence of blebs increases the sensitivity of mRNA-LNP to freeze-drying-induced stress. In the present study, using an influenza A virus hemagglutinin (HA) mRNA in LNP that were structurally similar to that in the COVID-19 mRNA vaccines currently in clinic, we studied the effect of TFFD on the physical properties, internal structure, as well as immunogenicity of the HA mRNA-LNP vaccine. We concluded that TFFD can be utilized to prepare dry powders of the HA mRNA-LNP, but a sufficient amount of excipients were needed to minimize changes in the physical properties, structure, and immunogenicity of the HA mRNA-LNP vaccine.

Scorpion-inspired multi-scale contact enabled multifunctional piezoresistive pressure sensor based on hybrid nanofiber decoration

Inspired by the slit organs of scorpions, an array narrow orifice configuration (ANOC) piezoresistive foam sensors are developed by decorating hybrid polypyrrole (PPy)/ carbon nanotubes (CNT) nanofibers on the foam strut. The developed ANOC composite foam exhibits a unique multi-scale contact sensing mechanism enabled by the macro-scale internal dome structures, the micro-scale struts of the porous foam, the nano-scale PPy/CNT hybrid conductive networks, and the nano-scale friction of the rough CNT/PPy hybrid nanofibers (NFs), which rendered the ANOC composite foam an ultra-high sensitivity of 1.8 kPa−1 at low pressure within 1.5 kPa. When used as a piezoresistive pressure sensor, the ANOC composite foam exhibits a wide detection range (0 %-70 %), fast response/recover time (120/90 ms), and long-term stability and fatigue resistance (over 80000 s), and demonstrated capability to monitor various human activities. A smart cushion integrated with an array of foam sensors can accurately identify the human sitting positions and posture rectifying. Moreover, owing to the highly porous conductive network and the doped ions, the ANOC composite foam can generate energy from saline water and serve as a water-induced energy generation (WIEG) device for direct energy supply. This research paves the way for the development of multifunctional high-performance.

Study on Vibration and Failure of Transverse Flow Turbine Based on Fluid–Structure Interaction

During the operation of a turbine, the water level drop can cause vibration and damage to the flow components, severely threatening its stability and reliability. Investigating the impact of operational parameters on the internal flow field and flow structures of tidal turbines under low flow conditions is crucial for peak shaving and deployment of tidal power stations. This paper takes a 24[Formula: see text]MW turbine as the research object, using numerical calculations to analyze the effects of tailwater height on the flow characteristics and structural properties of the unit under low flow conditions. It studies the hydraulic impact on the flow component walls under different operating parameters and verifies the reliability of numerical calculations through vibration and stress tests. The results show that the increase in tailwater level affects the turbine’s flow characteristics, forming large-scale, high-intensity vortices in the internal flow field and causing pressure pulsations near the wall surface. Modal analysis reveals that under different tailwater heights, the maximum modal effective mass exists along the axis of the impeller, with modal frequencies higher than the main frequencies of pressure pulsations. The impeller region corresponds to the turbine chamber wall bearing significant stress, which induces strain. The magnitude of stress and the degree of strain are positively correlated with the tailwater height. The research findings provide guidance for tailwater regulation and stable operation of tidal power stations.

Ignition and Combustion of Aluminum Hydride Dust Aerosols

ABSTRACT The results of comparative experimental studies of aluminum hydride AlH3 and aluminum Al particle aerosols, in particular, of the critical conditions for auto-ignition and the features of the flame propagation in low-volume (V ≈ 5.1·10−3 m3) and large clouds (volume is varied from 40 to 60 m3) are presented in this article. Experiments have shown that for aerosols of AlH3 particles, the auto-ignition temperature is much lower than for aluminum particles. This is due to the thermal decomposition of aluminum hydride into hydrogen and active aluminum. The laminar flame was studied in low-volume clouds. A two-frontal form of a laminar flame wave in AlH3 aerosol was found. Moreover, the visible flame propagation speeds for AlH3 correspond to those for finely dispersed Al and are two times higher compared to coarse Al. The turbulent flame in the large free clouds of aluminum hydride dusts has flame propagation speeds several times higher than those in the aluminum clouds and is characterized by the formation of a toroid vortex with a complex internal structure.

Geology and geochronology of the El Peñón granitic pluton: A contribution to the famatinian magmatic evolution in the Sierra de San Luis, Argentina

The El Peñón pluton is a peraluminous granite located in the northeastern sector of the Sierra de San Luis. According to its textural and mineral variations two endmember facies have been distinguished along it: a coarse-grained muscovite-bearing facies, and a fine-grained biotite-bearing facies. Field relationships aligned with mineralogical and geochemical compositions, allow us to establish an anatectic origin for this pluton. Regarding the inherited zircon ages, the provenance area of the metasedimentary source could be linked to the orogenic systems of Western Gondwana. The analysis of the internal structure of the intrusive body related with the structural arrangement observed in the country rocks indicates a syn-kinematic emplacement of the igneous body with respect to the main deformational event described in the Sierra de San Luis, which has been assigned to the closure of the Famatinian arc. New U-Pb (LA-ICP-MS) zircon ages constrain the emplacement/crystallization age of the El Peñón granite within the time lapse between ∼470 and 460 Ma. The geochronological data presented here, together with geochemical and structural analysis, enables us to correlate the origin of the El Peñón pluton and the deformation that occurred during its emplacement with the Famatinian Orogeny. Thus, these results allow us to rule out the presence of Pampean magmatism in the Sierra de San Luis but also establish a new absolute age for the main deformational event of the range.

Influence of micro-arc oxidation on the microstructure and dielectric properties of anodic aluminum oxide

To improve the dielectric performance of the anodic alumina film used in aluminum electrolytic capacitors, this study comparatively investigated the microstructure and dielectric properties of anodic aluminum oxide obtained through micro-arc oxidation (MAO) and conventional anodic oxidation (CAO). It is found that from the perspective of microstructure, the internal structure of the MAO treated oxide film has more and larger pores than that of CAO. This was attributed to the generation and overflow of numerous oxygen bubbles from within the oxide film at the locations where plasma sparks occurred during the process, thus forming larger pores. Regarding dielectric properties, the leakage current of the oxide film after MAO treatment was significantly reduced compared to CAO, with reductions of 58%, 56%, 64%, and 74% for the tested electrolytes Y1–Y4, respectively.