Outer Sheet Research Articles

Remodeling of Uterine Tissues During Gestation of Potamotrygon wallacei (Elasmobranchii), a Neotropical Freshwater Stingray Endemic to the Negro River, Central Amazonia.

Neotropical freshwater stingrays of the subfamily Potamotrygoninae exhibit aplacental viviparity with uterine trophonemata. In this reproductive mode, females nourish and provide oxygenation to the embryo via the mucosa of the uterine wall. The aim of this study was to describe and histologically quantify the tissue components of the gravid uterus in an Amazonian freshwater stingray. Adult females of Potamotrygon wallacei were studied in different reproductive periods: resting stage, pregnant, and postpartum. During reproductive rest, the left ovary has numerous follicles compared to the right side. Therefore, uterine fertility is usually higher on the left side. The presence of an embryo in the right uterus suggests that the right ovary is also functional, although this only occurs in larger females. In females at reproductive rest, the wall of the uterus is formed by a mucosal layer (without the trophonemata) that contributes 16.7% to the thickness, while the myometrium accounts for 83.3% of the thickness. The mass-specific volume of the mucosal layer, inner circular, and outer longitudinal smooth muscle sheets tend to increase in the gravid uterus, indicating hypertrophy and hyperplasia of these components. During pregnancy, the trophonemata undergo marked tissue remodeling. Epithelial cells are organized into glandular acini and have apical secretory vesicles; furthermore, peripheral blood vessels proliferate and become dilated. These characteristics demonstrate that the gravid uterus of P. wallacei presents intense uterolactation activity and provides oxygenation to the fetus. Tissue remodeling occurs only in the uterus with the presence of an embryo. During postpartum, females have low body condition factor indicating a high reproductive cost. This study contributes to the knowledge of the reproductive biology of this species and will help us understand the impacts of climate change on the breeding areas of potamotrygonids.

Ageing behaviour of folded joints produced by fusion bonding of an outer metal sheet and an inner organic sheet

Adhesive hemming is a process used in the automotive industry to join two metal sheets with good structural performance and good optical appearance of the rim. A new approach is to replace the inner metal sheet by a fibre-reinforced thermoplastic polymer sheet. The joining method used is fusion bonding. This can reduce process time, cost and weight of the finished part. As process route cold hemming is used where the outer metal sheet is first folded around the inner organic sheet at room temperature and afterwards thermally joined by induction. The aim of this work in particular is to investigate the behaviour under accelerated ageing conditions. Especially the cathodic dip coating as corrosion prevention and the air in the fold were varied. The latter can vary in the production process due to manufacturing. In addition, a pre-treatment of the metal surface with a laser was investigated to enhance the mechanical strength of the joint. The samples were produced with a three-step hemming process combined with inductive heating. The applied materials were an organic sheet made of polyamide-6 as matrix material and zinc coated steel. Conditioning according to DIN 1110 and the ageing test VDA 233-102 were applied to laboratory samples. It was shown that conditioning of the specimen reduces the maximal pull out force only slightly while ageing according to VDA 233-102 decreases the pull out force by about 50 %. Furthermore, the air gap has a significant influence on the ageing behaviour of the specimen while the cathodic dip coating only prevents the steel from corrosion but has no influence on the bond strength.

Fatigue properties of riveted joints under different hole perpendicularity errors and squeeze forces.

Riveting is the most important method of joining sheet metal and is widely used in the assembly of aircraft components. The perpendicularity error of the holes is unavoidable during automatic drilling and riveting, which has a significant impact on the quality of the assembly. In this paper, the effects of hole perpendicularity error and squeeze force on the interference fit size, interface contact state, microstructure morphology, fatigue life, and fracture form of riveted joints were investigated experimentally. The results show that the interference fit size increases with a greater tilt angle. When the tilt angle is 0°, the rivet shank is in close contact with the inner and outer sheets, and there is no obvious gap at the interface between the rivet and the sheets. As the tilt angle increases to 2° and 4°, a gap appears at the interface of regions 1, 2, and 3, while the rivet shank at region 4 is in close contact with the outer sheet. The fatigue life decreases when the tilt angle increases from 0° to 4°. For the same tilt angle, the fatigue life of riveted joints with a 0° tilt direction is higher than that of riveted joints with a 180° tilt direction. Increasing the squeeze force can to some extent reduce the adverse effect of the tilt angle on the fatigue life. The hole perpendicularity error does not affect the failure form, while the squeeze force has a significant effect on the failure form of the specimens. RESEARCH HIGHLIGHTS: The fatigue life of riveted joints decreases as the tilt angle increases. The size of the interfacial gap increases with increasing tilt angle. Higher fatigue life at 0° tilt direction than at 180° tilt direction. Increasing the squeeze force can somewhat reduce the negative effect of tilt angle on fatigue life.

A novel joining technology for metal and polymer sheets

This paper introduces a novel joining process for producing hybrid metal-polymer joints. The process, called hole hemming, involves deforming the metal sheet to establish a mechanical interlock with the polymer sheet, requiring neither heating nor auxiliary elements. The applicability of this process is tested for joining aluminum and polycarbonate (PC) sheets. Initially, an analytical design method is presented to achieve a connection without failure and with a mechanical interlock. Subsequently, the accuracy of the predictions is assessed through experiments and finite element simulations, employing the modified Mohr-Coulomb criterion for the prediction of ductile damage. Additionally, a new design for hole-hemmed joints, involving the incorporation of branches in the hole of the outer sheet, is introduced to expand the process window of this novel joining technology. Finally, the mechanical behavior of four different types of hybrid hole-hemmed joints (HHH joints) are evaluated through single-lap shear tests. The results show that the hole hemming process can successfully join AA6082-T4 and PC sheets, validating the proposed designs and ideas. The new hybrid joints demonstrate a maximum force and displacement of 1.6 kN and 12.9 mm, respectively, in the shear test, indicating significant potential of the proposed technology for joining metal and polymer sheets.

EXPERIMENTAL STUDY OF THE SPRAY PATTERN AND MERGER PROCESS OF DUAL-LAYER, ROTATING CONICAL LIQUID SHEETS

To obtain a comprehensive understanding of the primary breakup mechanism of dual-layer, rotating conical liquid sheets, the spray field of a dual-orifice, pressure-swirl atomizer is observed using high-speed shadowgraphy. The influences of the pressure drop in the primary and pilot flow channels and of the merger of the dual-layer liquid sheet on spray morphology, spray cone angle, and liquid sheet surface fluctuations are investigated on the basis of an analysis of spray field images. Attention is focused on the mechanisms underlying the behavior of the disturbance waves generated during the merger of the dual-layer liquid sheet. The results of this study reveal that the pressure drops in the primary and pilot flow channels affect the spray pattern, spray cone angle, and liquid sheet surface fluctuations. It is found that the influence of the pressure drop in the primary channel is dominant, and the changes in the liquid sheet surface fluctuations are related to the spray pattern. During liquid sheet merger (after the inner sheet has reached the expected spray cone angle), the spray cone angle of the outer sheet decreases, and only after the sheets are in contact with each other does the amplitude of the surface fluctuations become significantly larger and generate more medium- and high-frequency disturbance waves.

Properties of Quiet Magnetotail Plasma Sheet at Lunar Distances

AbstractThe Earth's magnetotail at lunar distances (R ≈ 60 RE) serves as a unique laboratory to study plasma dynamics in a weak, highly fluctuating magnetic field with a strong magnetic field gradient. In particular, studies of the of quiet‐time plasma in the lunar‐distant magnetotail can inform us about plasma entry to the magnetosphere and sources of magnetospheric plasma populations. We use the data collected by the two lunar‐orbiting Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft during its 2013–2019 magnetotail traversals to infer the average thermodynamic and spectral properties of plasma populations in the quiet‐time (i.e., low geomagnetic activity and absence of fast plasma flows) magnetotail at lunar distances. We found that plasma temperature and density in the quiet‐time magnetotail at R ≈ 60 RE are organized by the magnetic field. Three distinct regions with plasma β ≫ 1, β ∼ 1, and β ≪ 1, the central plasma sheet (CPS), outer plasma sheet (OPS), and lobes are sampled. We found that temperatures and energy spectra of ion populations in CPS, OPS, and lobes regimes are different: the hotter CPS temperatures scale with the kinetic energy of solar wind protons; cold OPS/lobe ions are, likely, of ionospheric origin. The ion and electron particle spectra in CPS, OPS, and lobes are nonthermal and reasonably well fitted by the Kappa function, with κ exponent varying between 2.5 and 3.5.

Fast and Long‐Lasting Potassium‐Ion Storage Enabled by Rationally Engineering Strain‐Relaxation Bi/Bi2O3 Nanodots Embedded in Carbon Sheets

AbstractBismuth (Bi)‐based materials merit high theoretical volumetric specific capacity (3800 mAh mL⁻1) but suffer from huge volume variations and sluggish reaction kinetics during cycling. Herein, the optimal framework of Bi/Bi2O3 nanodots enriched in suitable outer amorphous carbon sheets (Bi/Bi2O3 NDs@CSs) is first proposed to alleviate volume variations and accelerate stable charge transport to boost K+ storage performance. The introduction of proper Bi2O3 not only provides an efficient K+ adsorption path, but also effectively buffers volume changes via conversion reaction. Accordingly, the as‐prepared anode exhibits a remarkable rate capability (149.3 mAh g−1 at 60 A g−1, 42% capacity retention with a 120‐fold current‐density increase) and extraordinary durability (1800 cycles at 5.0 A g−1, 95% capacity retention), among the best rate and cycling performance to date in potassium ion batteries (PIBs) anodes. Theoretical calculations reveal the feasible structures of Bi/Bi2O3 NDs@CSs with double protection of carbon sheets and Bi2O3 are conducive to enhance charge transfer and efficiency of electrochemical reaction. Substantial in situ/ex situ characterizations and finite element simulation further unveil high reversibility and robust mechanical behavior of Bi/Bi2O3 NDs@CSs, favorable for the reinforcement of structural stability. This study provides new insights into developing high‐performance and durable Bi‐based anodes for PIBs.

Ductile Fracture Prediction in Hole Hemming of Aluminum and Magnesium Sheets

The present work proposes a suitable approach for predicting ductile fracture in a new joining process by plastic deformation called hole hemming. This process creates a combined form- and force-fit joint and enables the joining of lightweight materials with varying formability without requiring heating or auxiliary elements. In this process, the joinability of materials is limited by the occurrence of fracture in the outer sheet, highlighting the crucial need to accurately predict its damage during the process design phase. In this study, five different fracture criteria, including the McClintock, Rice–Tracey, Normalized Cockroft–Latham, and Brozzo and Modified Mohr–Coulomb (MMC) criteria, are examined during the joining of a challenging combination of lightweight materials (aluminum AA6082-T4 and magnesium AZ31). These criteria are calibrated by a hybrid experimental–numerical method using three tests with distinct stress states. These criteria are then implemented into the finite element model of the hole hemming process, utilizing an appropriate user subroutine. The results show that the flange edge of the outer sheet is the most prone region to fracture during the joining process, and a criterion must be able to model the fracture behavior of the material from uniaxial tension to shear to accurately predict fracture in this area. Among the examined criteria, only the MMC criterion was capable of such modeling and accurately predicted the critical displacement of the punch in the hemming stage with a negligible error (about 1%). On the other hand, the prediction accuracy of the other criteria varied significantly depending on the calibration test, resulting in errors ranging from 8.6% to 75.5%. The error of 8.6% was achieved with the Normalized Cockroft–Latham criterion calibrated by a uniaxial tension test. Thus, based on the results, the MMC criterion is recommended for ductile fracture prediction in the hole hemming process, offering valuable insights to assist in process design.

Capacitive behavior dominated persistent lithium storage in the 3D carbon nanofibers with 1D molybdenum sulfide

As the anode material of lithium ion battery, molybdenum disulfide (MoS2) has a theoretical capacity far exceeding that of graphite. However, its development is greatly limited by the structural changes and low conductivity during the cycle. Here, we prepared three-dimensional (3D) nitrogen doped carbon nanofibers embedded with MoS2 nanorods by electrospinning and hydrothermal methods. One dimensional (1D) MoS2 nanorods are perfectly distributed in the carbon nanofibers along the axial direction, improving the stability and promoting the rapid insertion/removal of lithium ions. The outer molybdenum sulfide sheet provides more reactive sites, and the hierarchical nanostructures with high conductivity are constructed to obtain lithium ion storage materials dominated by high capacitance behavior. At the same time, it maintains the capacity of 736.7 mAh/g under the high current density of 5 A/g, showing excellent long cycle stability. This work provides a new possibility for the study of long cycle stable lithium ion storage at high rates.

One-step solution-induced impregnation synthesis of strongly coupled platinum–molybdenum/silicon carbide quantum dots heterostructures encapsulated on reduced graphene oxide sheet as electrocatalyst for hydrogen evolution reaction

Strongly coupled platinum-based transition-metal oxide/carbon hybrids and the development of quantum-dot structures of hybrid catalysts are cost-effective and maximize accessible active sites. However, a significant obstacle still exists for the rational proposal and simple synthesis of hybrid quantum-dot material catalysts. Herein, novel PtxMo1-xSiC quantum dots encapsulated in reduced graphene oxide (rGO) (PtxMo1-xSiC QDs @rGO) for catalyzing the hydrogen evolution reaction (HER) were fabricated through a simple solution-induced impregnation method. The optimized Pt5Mo95SiC QDs @rGO catalyst only require overpotentials of 18 mV and 25 mV to deliver current densities of 10 mA cm−2 and 250 mA cm−2 in acidic media, respectively. The synergistic effects of the inner PtxMo1-xSiC QDs networks and outer conductive rGO sheets that promote electron transfer are responsible for the outstanding HER performance. This work presents a novel method for producing an extremely effective HER catalyst for applications on large-scale.

Artifacts’ Detection for MRI Non-Metallic Needles: Comparative Analysis for Artifact Evaluation Using K-Means and Manual Quantification

Interventional biopsy needles need to be accurately localized to the target tissue during magnetic resonance imaging (MRI) interventions. In this context, severe susceptibility artifacts affect the visibility of structures in the MR images depending on the needle’s material composition. In particular, standard needles for the spinal cord made of nickel-titanium alloys (NiTi) generate massive susceptibility artifacts during MRI. Consequently, this does not allow the precise placement of the needle to the target. The aim was to prove that using a non-metallic material for the needle can significantly reduce the appearance of artifacts. Hence, this work used a new combination of non-metallic materials based on an enforced fiber bundle as an inner core with different outer hollow sheets to fabricate seven prototypes of interventional spinal needles to optimize their visualization in MRI scans. Susceptibility artifacts for the non-metallic needles were evaluated in MRI images by an automatic quantification based on a K-means algorithm and compared with manual quantification. The width and length of the artifacts were measured for each needle. The non-metallic needles showed significantly lower artifacts in comparison to the standard needle. K-means provided the capability for detecting needle artifacts in MRI images, facilitating qualitative and quantitative assessment of MRI artifacts.

Inter-quintuple layer coupling and topological phase transitions in the chalcogenide topological insulators

Driving quantum phase transitions in the 3D topological insulators offers pathways to tuning the topological states and their properties. We use DFT-based calculations to systematically investigate topological phase transitions in Bi2Se3, Sb2Se3, Bi2Te3 and Sb2Te3 by varying the ratio of lattice constants. This ensures no net hydrostatic pressure under anisotropic stress and strain and allows a clear identification of the physics leading to the transition. As a function of , all of these materials exhibit structural and electronic stability of the quintuple layers (QLs), and quasi-linear behavior of both the inter-QL distance and the energy gap near the topological transition. Our results show that the transition is predominantly controlled by the inter-QL physics, namely by competing Coulomb and van der Waals interactions between the outer atomic sheets in neighboring QLs. We discuss the implications of our results for topological tuning by alloying.

Zirconium-based MOF nanocrystals confined on amphoteric halloysite nanotubes for promoting the catalytic hydrolysis of an organophosphorus nerve agent simulant.

Exploiting efficient and practical catalysts for hydrolyzing organophosphorus nerve agents is significant and highly desirable. Herein, a new class of self-detoxifying composites, namely, halloysite nanotubes@NU-912 (HNTs@NU-912), HNTs@NU-912-I and HNTs@UiO-66-NH2, is constructed by in situ synthesis of hexanuclear zirconium cluster-based metal-organic frameworks (Zr-MOFs) NU-912, NU-912-I and UiO-66-NH2, respectively, with HNTs, which are natural nanotubular materials consisting of Si-O-Si tetrahedral sheets on the outer surface and Al-OH octahedral sheets on the inner surface. The results show that crystalline Zr-MOFs uniformly cover the outer surface of HNTs and the particle size of Zr-MOFs is greatly reduced to less than 50 nm. Furthermore, HNTs@NU-912, HNTs@NU-912-I and HNTs@UiO-66-NH2 display much higher catalytic efficiency for the hydrolysis of dimethyl-4-nitrophenyl phosphate (DMNP) than the corresponding Zr-MOFs both in an aqueous N-ethylmorpholine (NEM) buffer solution and under ambient conditions. Specifically, HNTs@NU-912-I shows a turnover frequency (TOF) of 0.315 s-1 in aqueous buffer solution, placing it among the best Zr-MOF-based heterogeneous catalysts for the hydrolysis of DMNP. The composites show high stability, and more importantly, can replace the buffer solvent and control the pH to a certain degree by virtue of its acidic Si-O-Si sheets and alkaline Al-OH sheets. This work provides a certain reference for the subsequent development of personal protective equipment.

Susceptibility artifacts evaluation for non-metallic biopsy needles in a biological-engineered 3D tumor model

Abstract Nowadays, needle artifacts are an essential restriction for MRI-guided interventions, as they influence the visually perceived needle size and needle destination. Standard MRI needles made of Nickel-Titanium (NiTi) alloys still produce massive artifacts in MRI due to materials’ interactions with the magnetic environment. The use of non-metallic materials can reduce these artifacts. Therefore, we propose a nonmetallic concept of a coaxial needle design concept with a fiber-enforced inner core and an outer polymeric hollow sheet. This work aims to evaluate the artifact performance of the proposed needles in a custom-made three-dimensional (3D) tumor model with a relevant size and thickness for medical interventions under MRI guidance using a 3T field strength with a T1-weighted gradient-echo sequence. Three coaxial MRcompatible needles were inserted in the custom-made 3D tissue phantom, one standard needle from NiTi, and two proposed non-metallic needles. Artifact’s width and length were measured for each needle. Overall, the non-metallic needles showed significantly lower artifacts than the standard NiTi needle inside the 3D tumor model.

Prediction of Spherical Sheet Springback Based on a Sparrow-Search-Algorithm-Optimized BP Neural Network

Springback is an unavoidable problem in cold-forming processes and affects the efficiency and quality of the processing of outer sheets for ships. Therefore, effective control and prediction of sheet-forming springback is particularly important in the field of cold-bending processes. To this end, this paper presents research on cold-bending springback prediction based on a study of the multipoint cold-bending process combined with intelligent algorithms, as well as research on the multipoint cold-bending production of ship-hull plates. The forming process of spherical sheets was simulated by a finite element simulation. The amount of springback under different processes was studied, and the forming state and springback state were briefly analyzed. Then an in-depth study of machine learning was carried out, and the sparrow search algorithm (SSA) was introduced based on a back-propagation neural network (BPNN). The purpose of this integration was to prevent the BP neural network model from falling into local optimal solution problems. Then simulation data were obtained with the help of a simulation to build a backpropagation neural network prediction model, which was optimized based on the sparrow search algorithm, and training tests were conducted. Then the prediction results of the model were compared with the simulation data to verify that the prediction accuracy performance of the sparrow-search-algorithm-optimized BPNN model was improved. Finally, the prediction model based on the SSA–BPNN algorithm was compared with the prediction models of different algorithms, and the prediction results showed that SSA–BPNN outperformed other algorithms in prediction accuracy and speed; its prediction error was within 4%, which meets on-site processing requirements. The sparrow-search-algorithm-based optimization of BPNN was confirmed to have strong applicability in springback prediction.

Enhanced cycling performance of SiOx microparticles uniformly coated with graphene sheets

Microsized silicon suboxide (SiOx, 0<x<2) materials promise less interfacial side reactions and higher volumetric capacity than those of nanosized couterpart when used as anode materials for high energy density lithium ion batteries. However, its poorer mechanical stability during charge/discharge process severely frustrates the cycling performance. Here we successfully achieved a conformally graphene-coated microsized SiOx material through surface engineering by a facile PVP-assisted hydrothermal method. PVP connects SiOx and graphene oxide (GO) sheets via hydrogen bonds in hydrothermal process and then in-situ carbonizes to form an amorphous carbon layer between SiOx core and graphene sheets after heat-treatment. The inner amorphous carbon layer and outer graphene sheets together evenly and conformally coat on SiOx particles, forming a double-layer coated SiOx/C@graphene composite. The well-encapsulation of SiOx by the double coating layers guarantees the uniform occurrence of electrode reactions on SiOx surface, which reduces the structural stress and homogenizes the volume variation, thus enabling excellent structural integrity of electrode during lithiation/delithiation process. Owing to the well-engineered structure, the SiOx/C@graphene electrode delivers an excellent cyclic performance (1076 mAh g−1 at 0.5C after 120 cycles with a capacity retention of 88.7%) and superior rate capability (785 mAh g−1 at 3C).

Morphologically-different cells and colonies cause distinctive performance of coagulative colloidal ozone microbubbles in simultaneously removing bloom-forming cyanobacteria and microcystin-LR

Morphology, the important feature of bloom-forming cyanobacteria, was studied for its impacts on the harmful cyanobacterial bloom (HCB) treatment by coagulative colloidal ozone microbubbles (CCOMBs). The globally-appeared HCB species – Microcystis aeruginosa (spherical cells, block mass colonies), Microcystis panniformis (spherical cells, flat penniform-like colonies) and Anabaena flos-aquae (filamentous morphology) were chosen as representative species. CCOMBs were generated by modifying the bubble surface and the gas core with coagulant and ozone, respectively. The removal of spherical cells and filaments was > 99.5% and ≤ 34.6%, individually, and the latter was ascribed to chain breakage. CCOMBs collected Microcystis panniformis via complexing with the fluorescent and non-fluorescent functional groups of cell colonies but captured Anabaena flos-aquae through the fluorescent ones. More Microcystis aeruginosa got membrane-damaged than Microcystis panniformis; nevertheless, the microcystin-LR (MC-LR) removal was guaranteed through efficiently oxidizing the released MC-LR. Although the outer peptidoglycan sheet of Anabaena flos-aquae was destroyed, the inner cyte membrane remained intact, preventing intracellular MC-LR from releasing. The HCBs dominated by single species with spherical cells were more readily treated than those with co-occurred species. The toxicological tests imply that, as a robust tool for HCB treatment, the CCOMB technology could be eco-environmentally friendly to the aquatic environment.

A free‐form surface flattening algorithm that minimizes geometric deformation energy

Based on the analysis of the advantages and disadvantages of existing surface flattening algorithms, this paper proposes a free-form surface flattening algorithm that minimizes geometric deformation by combining the advantages of the geometric flattening method and the mechanical energy flattening method to address the problems of many iterations, large changes in convergence, and weak visualization of deformation. The point cloud surface is meshed using the triangular slice search method, and the 3D surface mesh is wrapped around the surface using geometric mapping relationships. The initial correction and deformation analysis of the ring flatten graphic are carried out according to the average flattening error, and a global geometric deformation energy model is established to obtain the energy-minimizing unfolding conditions and optimize the initial flattening graph by iterative optimization. The verification of the algorithm shows that the algorithm is general, has good robustness, high flattening accuracy, and visualizes the flattening deformation. The method is suitable for some design occasions of machining, such as the flattening calculation of automobile outer cladding parts and sheet metal parts. It is especially suitable for the flattening calculation of ring-like parts, and is a good guide for the design calculation and stamping process of sheet-metal-like parts.

Numerical investigation of atomization of swirling liquid sheets using transforming algorithm

The atomization of swirling liquid sheets is investigated with numerical simulations. An algorithm that transforms the small Eulerian droplets into the Lagrangian particles is developed to reduce the computational errors in describing the interfaces. Different transforming criteria are evaluated and the grid scale criterion is shown applicable for atomization simulations of swirling sheets. Due to the complexity in the flow field, the inverse transformation is implemented when the Lagrangian particles move close to the resolved Eulerian liquid structures. First, the transforming algorithm is verified through a series of test cases. Then the algorithm is applied to investigate the atomization of a single swirling sheet. Characteristic vortical structures are identified near the interfaces. It is found that the sheet disturbances coincide with the recirculation regions. The mechanisms to break up hole structures are found to be related to surface tension and aerodynamic forces. The diameter distribution of droplets and number of liquid structures are consistent with realistic conditions. Finally the atomization of coaxial swirling liquid sheets, which is rarely investigated in detail in previous studies due to difficulties in experiments and numerical methods, is simulated with the presented algorithm. The atomization process is captured in detail. The inner and outer sheets collide and merge with each other to form a single sheet due to the pressure difference. A high pressure region at the impinging positions is generated by the strong momentum exchange between the sheets and it promotes the rapid breakup of the merged sheet. The spray characteristics and diameter distributions of droplets are obtained and compared under different injection conditions.

Analysis of the causes and areas of localization of wear of the outer plating of the hulls of inland and mixed (river-sea) navigation

This article analyzes the areas of localization of wear of the outer plating of the hulls of ships of inland and mixed (river-sea) navigation and the causes of them. It is noted that the problem of wear of outer plating sheets is associated with the tasks of ensuring watertightness and strength of ship hulls, on which the preservation of the functionality of ships as floating transport engineering structures depends. The results of the study show that: 1) wear of the outer skin of the vessels of inland and mixed (river-sea) navigation of the studied groups (pusher tugs, oil ore carriers, dry cargo and passenger ships) have different localization; 2) the localization of wear depends on the area of ​​operation, the main dimensions and design features of the ships; 3) wear is caused by corrosive, erosive and abrasive effects of the external environment, structural changes in the metal in welds and near-weld zones, as well as poor quality of paint and varnish protection of ship hulls, insufficient vibration damping of ship mechanisms, in some cases, unsatisfactory alignment of ship mechanisms and shafting; 4) local residual deformations (dents, crooks, ribbing), the frequency of their formation, the appearance and development of cracks in welds and the whole metal are due to the loss of stability of bonds due to their wear; 5) there is a correlation between the wear values and residual deformations of the outer skin sheets. Establishing the type of correlation dependence requires special study.