Search Results (30)

Although wind turbine installation vessels (WTIVs) are increasingly operating in deepwater complex geological areas with larger scales, systematic research on and experimental validation of platform jack-up stability remain insufficient. This study aimed to establish a comprehensive evaluation framework encompassing penetration depth, anti-overturning/sliding stability, and punch-through risk, thereby filling the gap in holistic platform stability analysis. An entire four-legged centrifuge test at 150× g was integrated with coupled Eulerian–Lagrangian (CEL) numerical simulations and theoretical methods to systematically investigate spudcan penetration mechanisms and global sliding/overturning evolution in clay/sand. The key findings reveal that soil properties critically influence penetration resistance and platform stability: Sand exhibited a six-times-higher ultimate bearing capacity than clay, yet its failure zone was 42% smaller. The sliding resistance in sand was 2–5 times greater than in clay, while the overturning behavior diverged significantly. Although the horizontal loads in clay were only 50% of those in sand, the tilt angles at equivalent sliding distances reached 8–10 times higher. Field validation at Guangdong Lemen Wind Farm confirmed the method’s reliability: penetration prediction errors of <5% and soil backflow/plugging effects were identified as critical control factors for punch-through risk assessment. Notably, the overturning safety factors for crane operation at 90° outreach and storm survival were equivalent, indicating operational load combinations dominate overturning risks. These results provide a theoretical and decision-making basis for the safe operation of large WTIVs, particularly applicable to engineering practices in complex stratified seabed areas. Full article

This study investigates the hydrogen permeability of injection-molded polyamide 6 (PA6) nanocomposites reinforced with organo-modified montmorillonite (OMMT) at varying concentrations (1, 2.5, 5, and 10 wt. %) for potential use as Type IV composite-overwrapped pressure vessel (COPV) liners. While previous work examined their mechanical properties, this study focuses on their crystallinity, morphology, and gas barrier performance. The precise inorganic content was determined using thermal gravimetry analysis (TGA), while differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and scanning electron microscopy (SEM) were used to characterize the structural and morphological changes induced by varying filler content. The results showed that generally higher OMMT concentrations promoted γ-phase formation but also led to increased agglomeration and reduced crystallinity. The PA6/OMMT-1 wt. % sample stood out with higher crystallinity, well-dispersed clay, and low hydrogen permeability. In contrast, the PA6/OMMT-2.5 and -5 wt. % samples showed increased permeability, which corresponded to WAXD and SEM evidence of agglomeration and DSC results indicating a lower degree of crystallinity. PA6/OMMT-10 wt. % showed the most-reduced hydrogen permeability compared to all other samples. This improvement, however, is attributed to a tortuous path effect created by the high filler loading rather than optimal crystallinity or dispersion. SEM images revealed significant OMMT agglomeration, and DSC analysis confirmed reduced crystallinity, indicating that despite the excellent barrier performance, the compromised microstructure may negatively impact mechanical reliability, showing PA6/OMMT-1 wt. % to be the most balanced candidate combining both mechanical integrity and hydrogen impermeability for Type IV COPV liners. Full article

The possibility of collecting new archaeological elements useful in reconstructing the dynamics of population, production and commercial activities in the Bronze Age at the edge of the central-southern Venice Lagoon was provided between 2023 and 2024 thanks to an intervention of rescue archaeology planned during some water restoration works in the Giare–Mira area. Three small excavations revealed, approximately one meter below the current surface and covered by alluvial sediments, a rather complex palimpsest dated to the late Recent and the early Final Bronze Age. Three large circular pits containing exclusively purified grey/blue clay and very rare inclusions of vegetable fibres, and many large, fired clay vessels’ bases, walls and rims clustered in concentrated assemblages and random deposits point to potential on-site production. Two pyro-technological structures, one characterised by a sub-circular combustion chamber and a long inlet channel/praefurnium, and the second one with a sub-rectangular shape with arched niches along its southern side, complete the exceptional context here discovered. To analyse the relationship between the site and the natural sedimentary succession and to evaluate the possible extension of this site, three electrical resistivity tomography (ERT) and low-frequency electromagnetic (FDEM) measurements were collected. Several manual core drillings associated with remote sensing integrated the geophysical data in the analysis of the geomorphological evolution of this area, clearly related to different phases of fluvial activity, in a framework of continuous relative sea level rise. The typology and chronology of the archaeological structures and materials, currently undergoing further analyses, support the interpretation of the site as a late Recent/early Final Bronze Age productive site. Geophysical and geomorphological data provide information on the palaeoenvironmental setting, suggesting that the site was located on a fine-grained, stable alluvial plain at a distance of a few kilometres from the lagoon shore to the south-east and the course of the Brenta River to the north. The archaeological site was buried by fine-grained floodplain deposits attributed to the Brenta River. The good preservation of the archaeological structures buried by fluvial sediments suggests that the site was abandoned soon before sedimentation started. Full article

This study systematically analyzes the composition and microstructure of Neolithic pottery unearthed from the Dazhuzhuang, Likou, and Biting Sites in the Yongcheng District using techniques such as X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). The results show that although the raw materials for pottery at the three sites were likely sourced from nearby ancient soil layers, significant differences in chemical composition and manufacturing techniques are evident. Pottery from the Dazhuzhuang Site is mainly composed of argillaceous gray pottery, with relatively loose raw material selection and a wide fluctuation in SiO₂ content (64.98–71.07%), reflecting diversity in raw material sources. At the Likou Site, argillaceous black pottery predominates, characterized by higher Al₂O₃ content (17.78%) and significant fluctuations in CaO content (1.46–2.22%), suggesting the addition of calcareous fluxes and the adoption of standardized manufacturing techniques. Pottery from the Biting Site mainly consists of argillaceous gray pottery, showing higher Al₂O₃ content (17.36%), stable SiO₂ content (65.19–69.01%), and the lowest CaO content (0.84–1.81%). The microstructural analysis further reveals that the black pottery (from the Likou Site) displays dense vitrified regions and localized iron enrichment. In contrast, the gray pottery (from the Dazhuzhuang and Biting Sites) shows clay platelet structures and vessel-type-specific differences in porosity. This research provides important scientific evidence for understanding raw material selection, manufacturing techniques, and regional cultural interactions in the Yongcheng area during the Longshan Culture period. Full article

The archaeological materials from the Velika Humska Čuka site on the northern fringe of the Niš Basin in southeastern Serbia were analyzed to reveal the provenance of ceramics and other artifacts. This study focused on the elemental analysis of 61 samples, including local clay pits, potsherds, and whole vessels. Samples were chosen based on stylistic and typological characteristics to distinguish local and “foreign” pottery. Elemental analysis was conducted using energy-dispersive X-ray fluorescence (EDXRF) spectrometry, complemented by principal component analysis (PCA) for data interpretation. Results indicated that the majority of pottery samples, over 80%, were produced using local clay from deposits near the site. However, approximately 20% of the analyzed vessels were made using clay from deposits near the Bubanj site, 8 km south of Velika Humska Čuka. A vessel on a hollow high foot combining stylistic elements of the Bubanj-Hum I group and Early Eneolithic Pannonian groups was made of clay not sourced from any identified local deposits, suggesting its non-local origin. While the predominance of local materials suggests self-sufficient production, the use of non-local clays and stylistic influences highlights long-distance connections and exchanges. The study emphasizes the importance of Velika Humska Čuka in understanding the development of ceramic traditions and the cultural dynamics of the Early Eneolithic in the Central Balkans. Full article

The paper presents an interdisciplinary study based on an experimental model for investigating clay sources to identify prehistoric human behavior regarding resources. The study focuses on the Middle Bronze Age (1955/1773–1739/1614 cal. BC) settlement of Siliştea-Pe Cetățuie in eastern Romania, where archaeological materials from the Costișa and Monteoru cultures were discovered. Standard criteria for macroscopic analysis and analytical techniques, such as optical microscopy (OM), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Micro-Fourier Transform Infrared Spectroscopy (µ-FTIR), and thermal analysis (DTA and TG), were used to investigate the ceramic material from multiple points of view. The results showed that there were no significant differences between the ceramics of the two communities. Putting together the data obtained from macroscopic and physico-chemical analyses helped in partially reconstructing ancient human behaviors related to the production and use of ceramic vessels. Full article

This study focuses on polyamide 6/organo-modified montmorillonite (PA6/OMMT) nanocomposites as potential liner materials, given the growing interest in enhancing the performance of type IV composite overwrapped hydrogen storage pressure vessels. The mechanical properties of PA6/OMMT composites with varying filler concentrations were investigated across a temperature range relevant to hydrogen storage conditions (−40 °C to +85 °C). Liner collapse, a critical issue caused by rapid gas discharge, was analyzed using an Ishikawa diagram to identify external and internal factors. Mechanical testing revealed that higher OMMT content generally increased stiffness, especially at elevated temperatures. The Young’s modulus and first yield strength exhibited non-linear temperature dependencies, with 1 wt. per cent OMMT content enhancing yield strength at all tested temperatures. Dynamic mechanical analysis (DMA) indicated that OMMT improves the storage modulus, suggesting effective filler dispersion, but it also reduces the toughness and heat resistance, as evidenced by lower glass transition temperatures. This study underscores the importance of optimizing OMMT content to balance mechanical performance and thermal stability for the practical application of PA6/OMMT nanocomposites in hydrogen storage pressure vessels. Full article

The Amapá margin, part of the Brazilian Equatorial Margin (BEM), is a key region that plays a strategic role in the global climate balance between the North and South Atlantic Ocean as it is strictly tied to equatorial heat conveyance and the fresh/salt water equilibrium with the Amazon River. We performed a new scientific expedition on the Amapá continental shelf (ACS, northern part of the Amazon continental platform) collecting sediment and using instrumental observation at an unstudied site. We show here the preliminary outcomes following the applied methodologies for investigation. Geophysical, geological, and biological surveys were carried out within the ACS to (1) perform bathymetric and sonographic mapping, high-resolution sub-surface geophysical characterization of the deep environment of the margin of the continental platform, (2) characterize the habitats and benthic communities through underwater images and biological sampling, (3) collect benthic organisms for ecological and taxonomic studies, (4) define the mineralogical and (5) elemental components of sediments from the study region, and (6) identify their provenance. The geophysical data collection included the use of bathymetry, a sub-bottom profiler, side scan sonar, bathythermograph acquisition, moving vessel profiler, and a thermosalinograph. The geological data were obtained through mineralogical, elemental, and grain size analysis. The biological investigation involved epifauna/infauna characterization, microbial analysis, and eDNA analysis. The preliminary results of the geophysical mapping, shallow seismic, and ultrasonographic surveys endorsed the identification of a hard substrate in a mesophotic environment. The preliminary geological data allowed the identification of amphibole, feldspar, biotite, as well as other minerals (e.g., calcite, quartz, goethite, ilmenite) present in the substrata of the Amapá continental shelf. Silicon, iron, calcium, and aluminum composes ~85% of sediments from the ACS. Sand and clay are the main fraction from these sediments. Within the sediments, Polychaeta (Annelida) dominated, followed by Crustacea (Arthropoda), and Ophiuroidea (Echinodermata). Through TowCam videos, 35 taxons with diverse epifauna were recorded, including polychaetes, hydroids, algae, gastropods, anemones, cephalopods, crustaceans, fishes, and sea stars. Full article

Within the realm of archaeology, the analysis of biomolecules assumes significant importance in elucidating historical dietary patterns and their implications for contemporary contexts. To achieve this, knowledge and tools of both chemistry and archaeology are essential to yield objective outcomes and conduct analyses of archaeological materials for the detection of biomolecules. Usually, only minuscule remnants of ceramic fragments are retrieved from excavations, which limits the feasibility of comprehensive laboratory analysis. This study aimed to establish a protocol for analyzing fatty acids and starch from archaeological food utensils with minimal sample quantities. Various experiments were conducted to replicate preparations that might have occurred in archaeological vessels, aiming to establish the optimal protocol. The analyses were performed using clay griddles, subjecting vegetable oil to varying temperatures for fatty acid assessment. For starch analysis, a series of experiments encompassed diverse forms of potato preparations (pulp, chuño, tortilla, carbonization, and freeze-drying) and maize (flour, tortilla, and carbonization). The verification of the experiments was confirmed by conducting identical analyses, as developed in the current study, on authentic archaeological fragments. The principal outcomes of this investigation include the successful extraction of both types of biomolecules using only 0.25 g of the sample, obtained through direct scraping from the vessel. Soxhlet extraction was identified as the most efficient strategy to recover fatty acids. Additionally, a comprehensive protocol for the identification of starch extraction was developed. This study has, for the first time, elucidated two detailed methodologies for the extraction of fatty acids and starch in scenarios in which researchers can obtain limited quantities of archaeological food utensil fragments. Full article

Throughout history, ceramics have been the most abundant artifacts in archaeological discoveries. Within the Neolithic period in present-day Bulgaria, skilled artisans applied additional materials to decorate their pottery, evolving in composition and application techniques such as painting or incrustation. This study is focused on the investigation of white pigments used in decorating Early and Late Neolithic pottery from Madzherito, Kaloyanovets, and Hadzhidimitrovo—archaeological sites located in the Thracian Valley, Central South Bulgaria, affiliated with the cultural groups of Karanovo I and IV. Thirteen ceramic sherds were investigated through archaeometric techniques, including Fourier-transformed infrared spectroscopy in attenuated total reflection mode (ATR-FTIR) and laser-induced breakdown spectroscopy (LIBS). LIBS data underwent further analysis using principal component analysis (PCA). The results revealed that calcite, enriched with diverse fillers like quartz, clays, feldspars, and metal oxides, was the primary raw material for white decoration throughout the entire period. Talc emerged as an addition to calcite in the paint of two Early Neolithic sherds. The presence of hydroxyapatite and kaolinite in Late Neolithic pottery was also observed. The inclusion of supplementary ingredients in the primary formula for crafting white decorations signifies either the emergence of novel trends in manufacturing techniques or serves as evidence of vessels imported from adjacent territories. Full article

With the increasing popularity of automatic identification system AIS devices, mining latent vessel motion patterns from AIS data has become a hot topic in water transportation research. Trajectory similarity computation is a fundamental issue to many maritime applications such as trajectory clustering, prediction, and anomaly detection. However, current non-learning-based methods face performance and efficiency issues, while learning-based methods are limited by the lack of labeled sample and explicit spatial modeling, making it difficult to achieve optimal performance. To address the above issues, we propose CLAIS, a contrastive learning framework for graph-based vessel trajectory similarity computation. A combined parameterized trajectory augmentation scheme is proposed to generate similar trajectory sample pairs and a constructed spatial graph of the study region is pretrained to help model the input trajectory graph. A graph neural network encoder is used to extract spatial dependency from the trajectory graph to learn better trajectory representations. Finally, a contrastive loss function is used to train the model in an unsupervised manner. We also propose an improved experiment and three related metrics and conduct extensive experiments to evaluate the performance of the proposed framework. The results validate the efficacy of the proposed framework in trajectory similarity calculation. Full article

Since lead is a highly toxic metal, it is necessary to detect its presence in different samples; unfortunately, analysis can be complicated if the samples contain concentrations below the detection limit of conventional analytical techniques. Solid phase extraction is a technique that allows the carrying out of a pre-concentration process and thus makes it easy to quantify analytes. This work studied the efficiency of sorption and preconcentration of lead utilizing polysulfone (PSf) fibers grafted with acrylic acid (AA). The best conditions for Pb(II) extraction were: pH 5, 0.1 mol L⁻¹ of ionic strength, and 40 mg of sorbent (70% of removal). The sorbed Pb(II) was pre-concentrated by using an HNO₃ solution and quantified using flame atomic absorption spectrometry. The described procedure was used to obtain a correlation curve between initial concentrations and those obtained after the preconcentration process. This curve and the developed methodology were applied to the determination of Pb(II) concentration in a water sample contained in a handmade glazed clay vessel. With the implementation of the developed method, it was possible to pre-concentrate and determine a leached Pb(II) concentration of 258 µg L⁻¹. Full article

The article presents the palaeobotanical investigations of a remarkable discovery from the Early Chalcolithic settlement of Isaiia–Balta Popii (Romania), a multi-layered site. The excavation of a dwelling brought to light a rather rare finding, meaning a medium sized ceramic vessel having deposited inside two objects of burnt clay: an anthropomorphic figurine depicting pregnancy attributes and a small cone. Given the special character of the deposition, several samples from the vessel and near it were collected for phytolith analysis. Our results highlighted a ritual plant deposition: Elongate dendritic and Blocky morphotypes suggest that cereals and probably Artemisia seem to have been used for this purpose. These plants are known, aside from their practical uses, as powerful symbols, used through the ages in magic practices. All of these facts are strong arguments to interpret this find as a result of a ritual related to fertility involving both feminine and masculine symbols and plant use. Full article

This study investigated the behavior of the spudcan foundation of jack-up vessels of offshore wind turbines during the undrained vertical penetration into thin stiff-over-normally consolidated clay. Large deformation finite element (LDFE) analyses were used to simulate the continuous spudcan penetration into the seabed surface. Detailed parametric analysis was performed to explore a range of normalized soil properties and layer geometry and roughness of the soil–spudcan interface. The results were validated against previously reported data. The LDFE results were consistent with those of centrifuge tests. The evolving soil-failure patterns revealed soil backflow and the trapping of stronger top-layer material beneath the spudcan. The plug shape was influenced by the top layer thickness, the strength gradient of the bottom layer, and the relative strength ratio, which also affected the penetration resistance of soils. In this study, an expression was derived to quantify the plug shape with the aim of providing a theoretical basis for the design of spudcan footings with penetration resistance suitable for thin stiff-over-soft clay. Full article

Lead (Pb) as a pollutant is not biodegradable, tends to accumulate in different organisms, and can affect, for example, the performance of maize crops. However, only a few studies have reported on the effect of lead (Pb) and the relationship with the potential of hydrogen (pH) of water on crop performance. Thus, this study aimed at determining the influence of Pb and its relationship with the pH of water on the growth of Creole maize (Zea mays L.). In order to achieve this, a double bottom vessel system, isolated from the soil, was used to expose the plants to an aqueous Pb solution based on the equivalence of 1.5985 g of lead nitrate (Pb(NO₃)₂) per g of Pb. An experimental design of the two-factor response surface methodology (RSM) was applied. The Creole maize plants were exposed to four different concentrations of Pb in water [0 g L⁻¹ (P1: control); 0.33 g L⁻¹ (P2); 0.66 g L⁻¹ (P3); 1 g L⁻¹ (P4)], as well as to three different pH levels (5.5 (pH1); 6.5 (pH2); 7.5 (pH3)) in clay soil typical of the region. Subsequently, the relationship of these variables with maize growth was determined. The results showed a decrease in leaf growth, height, stem circumference, and root. However, it was also determined that these negative effects can be mitigated by controlling the pH of water in 7.5. Failure to control the combination of these two factors in the cultivation process generally results in an impact on the growth of the maize seedling. In addition, leaf discoloration was also observed in the leaves of maize plants from the concentration of 0.33 g L⁻¹ (P2), which suggests a nutritional anomaly that is toxic to the plant. Full article