Search Results (16)

This study investigates the shell hydroforming of 1.2 mm-thick AA5052 aluminum alloy sheets to produce hemispherical domes which possess inherent spatial symmetry about their central axis. Shell hydroforming is widely used in fabricating lightweight, high-strength components for aerospace, automotive, and energy applications. The forming process was driven by a spatially symmetrical internal pressure distribution applied uniformly across the blank to maintain balanced deformation and minimize geometrical distortion. Experimental trials aimed at achieving a dome depth of 50 mm revealed wrinkle formation at the blank periphery caused by circumferential compressive stresses symmetrical in nature with respect to the dome’s central axis. To better understand the forming behavior, a validated 3D finite element (FE) model was developed, capturing key phenomena such as material flow, strain rate evolution, hydrostatic stress distribution, and wrinkle development under symmetric boundary conditions. The effects of the internal pressure (IP), blank holding force (BHF), coefficient of friction (CoF), and flange radius (FR) were systematically studied. A strain rate of 0.1 s⁻¹ in the final stage improved material flow, while a symmetric tensile hydrostatic stress of 160 MPa facilitated dome expansion. Although tensile stresses can induce void growth, the elevated strain rate helped suppress it. An optimized parameter set of IP = 5.43 MPa, BHF = 140 kN, CoF = 0.04, and FR = 5.42 mm led to successful formation of the 50 mm dome with 19.38% thinning at the apex. Internal pressure was identified as the most critical factor influencing symmetric formability. A process window was established to predict symmetric failure modes such as wrinkling and bursting. Full article

Lymphocytes are generally non-adherent. This makes it challenging to fabricate three-dimensional (3D) structures mimicking the three-dimensional lymphoma microenvironment in vivo. This study presents the fabrication of a hemispherical 3D lymphoma model using the on-chip Cell Dome system with a hemispherical cavity (1 mm in diameter and almost 300 µm in height). Both the human brain lymphoma cell line (TK) and human B cell lymphoma cell line (KML-1) proliferated and filled the cavities. Hypoxic regions were observed in the center of the hemispherical structures. CD19 expression did not change in either cell line, while CD20 expression was slightly upregulated in TK cells and downregulated in KML-1 cells cultured in the Cell Dome compared to those cultured in two-dimensional (2D) flasks. In addition, both TK and KML-1 cells in the hemispherical structures exhibited higher resistance to doxorubicin than those in 2D flasks. These results demonstrate the effectiveness of the on-chip Cell Dome for fabricating 3D lymphoma models and provide valuable insights into the study of lymphoma behavior and the development of new drugs for lymphoma treatment. Full article

In this research, a streamlined numerical approach designed for the quick estimation of temperature profiles across the finite thickness of a hemispherical dome subjected to aerodynamic heating is introduced. Hemispherical domes, with their advantageous aerodynamic, structural, and optical properties, are frequently utilized in the front sections of objects traveling at supersonic velocities, including missiles or vehicles. The proposed method relies on one-dimensional analyses of fluid dynamics and flow characteristics to approximate the local heat flux across the exterior surface of the dome. By calculating these local heat flux values, it is also possible to predict the temperature variations within the thickness of the dome by employing the finite difference technique, to solve the heat conduction equation in spherical coordinates. This process is iterated over successive time intervals, to simulate the entire flight duration. Unlike traditional Computational Fluid Dynamics (CFD) simulations, the proposed strategy offers the benefits of significantly lower computational time and resource demands. The primary objective of this work is to provide an efficient numerical tool for evaluating aerodynamic heating impact and temperature gradients on hemispherical domes under specific conditions. The effectiveness of the proposed method will be validated by comparing the temperature profiles derived for a standard flight scenario against those obtained from 2-D axisymmetric transient CFD simulations performed using ANSYS-Fluent 2022 R2. Full article

Diamond-like carbon (DLC) has attracted significant attention in the recent decades because of its unique properties and applications. Ion beam assisted deposition (IBAD) has been widely established in industry due to the advantages of easy handling and scalability. In this work, a hemisphere dome model is specially designed as a substrate. The influence of the surface orientation on the coating thickness, Raman I_D/I_G ratio, surface roughness and the stress of the DLC films are examined. The reduction in the stress in the DLC films reflects the lower energy-dependence in diamond due to the varied sp3/sp2 fraction and columnar growth pattern. The variation of the surface orientation provides an efficient means of tailoring the properties and microstructure of the DLC films. Full article

An automatic geomagnetic station for monitoring the Earth’s magnetic field variations was installed in December 2020 at Talos Dome, a remote site on the Antarctic Plateau, about 300 km away from the permanent geomagnetic observatory at Mario Zucchelli Station (MZS). Designed and assembled at the laboratory of electronics of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome, this autonomous station is formed by a vector magnetometer specifically manufactured by Lviv Institute (Ukraine) for very low temperatures and a low-power system supplied by batteries charged by a wind generator and solar panel. Data, sampled at 1 Hz, are locally stored and can be downloaded once a year during the Antarctic summer expeditions. The goal was to integrate observatory data for better monitoring the geomagnetic field from an uncovered Antarctic area. In fact, it is well known that the distribution of geomagnetic observatories strongly favors the northern hemisphere, and each new instrumental installation in Antarctica should be considered as a useful attempt to balance the geomagnetic monitoring in the two hemispheres. The achieved goal was to obtain a long data series, keeping the station working even during the austral winter when the temperature can reach −60 °C; we recorded almost 11 months of data in one year and the station is still operating. Data from the new station, jointly with data from permanent observatories, improve the analysis of the magnetospheric dynamics and the ionosphere–magnetosphere coupling. Talos Dome, together with the Italian geomagnetic observatory at Mario Zucchelli Station and New Zealand geomagnetic observatory at Scott Base, constitutes a network along the 80°S geomagnetic parallel, which is interesting for studying the longitudinal propagation of geomagnetic signals of external origin. In this work we present the characteristics of the station and of the data it provides, with the aim of them for analysis in the framework of space weather. Full article

Human-hepatoblastoma-derived cell line, HepG2, has been widely used in liver and liver cancer studies. HepG2 spheroids produced in a three-dimensional (3D) culture system provide a better biological model than cells cultured in a two-dimensional (2D) culture system. Since cells at the center of spheroids exhibit specific behaviors attributed to hypoxic conditions, a 3D cell culture system that allows the observation of such cells using conventional optical or fluorescence microscopes would be useful. In this study, HepG2 cells were cultured in “Cell Dome”, a micro-dome in which cells are enclosed in a cavity consisting of a hemispherical hydrogel shell. HepG2 cells formed hemispherical cell aggregates which filled the cavity of Cell Domes on 18 days of culture and the cells could continue to be cultured for 29 days. The cells at the center of hemispherical cell aggregates were observed using a fluorescence microscope. The cells grew in Cell Domes for 18 days exhibited higher Pi-class Glutathione S-Transferase enzymatic activity, hypoxia inducible factor-1α gene expression, and higher tolerance to mitomycin C than those cultured in 2D on tissue culture dishes (* p < 0.05). These results indicate that the center of the glass adhesive surface of hemispherical cell aggregates which is expected to have the similar environment as the center of the spheroids can be directly observed through glass plates. In conclusion, Cell Dome would be useful as an evaluation platform for organized HepG2 cells. Full article

This paper systematically explains the methodology and results of empirical work on the development of a low-cost filament winding technology for manufacturing axisymmetric polymer composite structures with a high length-to-diameter ratio, such as tubes, motor casings, and pressure vessels. The principal objective was to examine the experiences and most optimal practices in the development of computer-controlled equipment and auxiliary tooling for the wet filament-winding process. To preclude expensive commercial software for the automated control of a winding machine, analytical equations were derived for the winding trajectory of a four-axis filament-winding machine. The feasibility of the proposed equations was successfully validated by laying the fiber along the geodesic path marked on the surface of a cylindrical mandrel with hemispherical ends. Moreover, the carbon/epoxy cylindrical casings with hemispherical ends and port openings of the same diameter were wound to determine the thickness distribution in the hemispherical dome. The fiber volume ratio in the wound composite parts was evaluated using an optical technique. Full article

The results are presented from a study of three-layer geodesic dome structures with bar fillers under their own weight. An algorithm was developed for selecting the type of structural layout used and the reference parameters chosen in terms of the technological, strength, and weight characteristics. The results of this analysis aim to make it easier for designers to determine the optimal reference parameters in the initial stage of the designing of geodetic hemispherical dome structures, the construction of which is planned to be carried out in remote areas with harsh climatic conditions. Due to the lack of sufficient ground transport infrastructure, cargo delivery to these regions is currently possible only with the help of air transport. The importance of this study rests on the lack of adequate methods for the determination of the reference parameters for geodesic hemispherical dome structures at an early stage of design. In particular, it is common for the issues regarding the transportation of structural elements as well as those that involve ensuring the strength and the technological characteristics of the structure to not be considered simultaneously. This study owes its relevance to the rapid development of the uninhabited territories of the Russian Federation in the context of the global ecological crisis caused by anthropogenic impact on the environment. Full article

A hemispherical research demonstration pavilion was presented to the public from April to October 2019. It was the first large-scale lightweight dome with a supporting roof structure primarily made of carbon- and glass-fiber-reinforced composites, fabricated by robotic coreless filament winding. We conducted monitoring to ascertain the sturdiness of the fiber composite material of the supporting structure over the course of 130 days. This paper presents the methods and results of on-site monitoring as well as laboratory inspections. The thermal behavior of the pavilion was characterized, the color change of the matrix was quantified, and the inner composition of the coreless wound structures was investigated. This validated the structural design and revealed that the surface temperatures of the carbon fibers do not exceed the guideline values of flat, black façades and that UV absorbers need to be improved for such applications. Full article

While more and more studies are being conducted on carbonaceous fractions—organic carbon (OC) and elemental carbon (EC)—in urban areas, there are still too few studies about these species and their effects in polar areas due to their very low concentrations; further, studies in the literature report only data from intensive campaigns, limited in time. We present here for the first time EC–OC concentration long-time data records from the sea-level sampling site of Ny-Ålesund, in the High Arctic (5 years), and from Dome C, in the East Antarctic Plateau (1 year). Regarding the Arctic, the median (and the interquartile range (IQR)) mass concentrations for the years 2011–2015 are 352 (IQR: 283–475) ng/m³ for OC and 4.8 (IQR: 4.6–17.4) ng/m³ for EC, which is responsible for only 3% of total carbon (TC). From both the concentration data sets and the variation of the average monthly concentrations, the influence of the Arctic haze on EC and OC concentrations is evident. Summer may be interested by high concentration episodes mainly due to long-range transport (e.g., from wide wildfires in the Northern Hemisphere, as happened in 2015). The average ratio of EC/OC for the summer period is 0.05, ranging from 0.02 to 0.10, and indicates a clean environment with prevailing biogenic (or biomass burning) sources, as well as aged, highly oxidized aerosol from long-range transport. Contribution from ship emission is not evident, but this result may be due to the sampling time resolution. In Antarctica, a 1 year-around data set from December 2016 to February 2018 is shown, which does not present a clear seasonal trend. The OC median (and IQR) value is 78 (64–106) ng/m³; for EC, it is 0.9 (0.6–2.4) ng/m³, weighing for 3% on TC values. The EC/OC ratio mean value is 0.20, with a range of 0.06–0.35. Due to the low EC and OC concentrations in polar areas, correction for the blank is far more important than in campaigns carried out in other regions, largely affecting uncertainties in measured concentrations. Through the years, we have thus developed a new sampling strategy that is presented here for the first time: samplers were modified in order to collect a larger amount of particulates on a small surface, enhancing the capability of the analytical method since the thermo-optical analyzer is sensitive to carbonaceous aerosol areal density. Further, we have recently coupled such modified samplers with a sampling strategy that makes a more reliable blank correction of every single sample possible. Full article

Species of the click-beetle genus Agriotes Eschscholtz are economically important crop pests distributed mainly in the Northern Hemisphere. They can inflict considerable damage on various field crops. Therefore, the detection, monitoring, and control of Agriotes include the adult trapping using species-specific sex pheromones, which is a critical component of pest research. To obtain a better understanding of the detailed antennal morphology as background information for subsequent chemical ecology research, we conducted a scanning electron microscopy study of the antennal sensilla of both sexes in 10 European Agriotes species. We identified 16 different sensilla in Agriotes, belonging to six main types: sensilla chaetica (subtypes C1 and C2), sensilla trichodea, sensilla basiconica (subtypes B1–B9), dome-shaped sensilla (subtypes D1 and D2), sensilla campaniformia, and Böhm sensilla. We discuss their possible functions and compare the sensilla of Agriotes with those of other Elateridae in order to consolidate the sensillum nomenclature in this family. Additionally, our study reveals the remarkable interspecific variability in sensillar equipment of Agriotes and identifies several characters of potential importance for future use in systematic studies. The present study provides a strong preliminary framework for subsequent research on the antennal morphology of this crop pest on a wider scale. Full article

The present work aims at studying the tensile behavior and formability of pre-painted steel sheets. To this purpose, uniaxial tensile and hemispherical punch tests were performed in order to analyze the deformation behavior of pre-painted sheets under uniaxial stretching and biaxial balanced stretching conditions, respectively. Tests were interrupted in order to obtain different strain levels until fracture; at each strain level reached, the occurrence of superficial damages on the paint coating was detected; thinning of the different layers of the pre-painted sheet was also measured. It was observed that the degree of damage on the paint coating depends on the loading condition; in particular, under uniaxial stretching, the paint coating is able to follow the steel sheet during deformation up to the onset of the necking, whilst, under biaxial balanced stretching, coating exhibits superficial damages before fracture of the sheet. Full article

The high-speed deformation behavior of friction stir-welded thin sheets in AA6082-T6 aluminum alloy, under biaxial balanced stretching, was investigated by means of a hemispherical punch test carried out using direct tension-compression Split Hopkinson Bar. The friction stir welding process was performed on thin sheet blanks using a pinless tool; the rotational and welding speeds were kept constant during process. The dynamic tests were carried out, with a punch speed of 4500 mm/s, at different punch stroke values until failure of the friction stir welded sample. It was seen that failure occurs along the welding line at a dome height about 11% higher than that at the onset of necking. Fractographic analysis shows that deformation is localized in the fracture zone. The results were compared with those obtained on friction stir welded blanks deformed under quasi-static condition in order to evaluate the influence of the loading rate on the weld deformation and fracture mechanisms. It was shown that joints deformed under dynamic loading condition are characterized by a dome height at the onset of necking significantly higher than the one measured under quasi-static condition. Full article

The significance of this work lies in the development of a novel code-based, detailed, and deterministic geometrical approach that couples the optimization of the Fresnel lens primary optical element (POE) and the dome-shaped secondary optical element (SOE). The objective was to maximize the concentration acceptance product (CAP), while using the minimum SOE and receiver geometry at a given f-number and incidence angle (also referred to as the tracking error angle). The laws of polychromatic light refraction along with trigonometry and spherical geometry were utilized to optimize the POE grooves, SOE radius, receiver size, and SOE–receiver spacing. Two literature case studies were analyzed to verify this work’s optimization, both with a spot Fresnel lens POE and a spherical dome SOE. Case 1 had a 625 cm² POE at an f-number of 1.5, and Case 2 had a 314.2 cm² POE at an f-number of 1.34. The equivalent POE designed by this work, with optimized SOE radiuses of 13.6 and 11.4 mm, respectively, enhanced the CAP value of Case 1 by 52% to 0.426 and that of Case 2 by 32.4% to 0.45. The SOE’s analytical optimization of Case 1 was checked by a simulated comparative analysis to ensure the validity of the results. Fine-tuning this design for thermal applications and concentrated photovoltaics is also discussed in this paper. The algorithm can be further improved for more optimization parameters and other SOE shapes. Full article

X-ray absorption near edge structure (XANES) measurements at the Fe K-edge were performed on aeolian dust in the TALos Dome Ice CorE drilling project (TALDICE) ice core drilled in the peripheral East Antarctic plateau, as well as on Southern Hemisphere potential source area samples. While South American sources show, as expected, a progressive increase in Fe oxidation with decreasing latitude, Antarctic sources show Fe oxidation levels higher than expected in such a cold polar environment, probably because of their very high exposure ages. Results from the TALDICE dust samples are compatible with a South American influence at the site during MIS2 (marine isotopic stage 2, the last and coldest phase of the last glacial period), in particular from Patagonia and Tierra del Fuego. However, a contribution from Australia and/or local Antarctic sources cannot be ruled out. Finally, important changes also occurred during the deglaciation and in the Holocene, when the influence of Antarctic local sources seems to have become progressively more important in recent times. This research is the first successful attempt to extract temporal climatic information from X-ray absorption spectroscopic data of the insoluble mineral dust particles contained in an ice core and shows the high potential of this technique. Full article