Search Results (110)

Ship structures are subjected to cyclic loading from waves and currents during operation, which can lead to fatigue failure, particularly at locations with structural discontinuities such as welds. Although various fatigue assessment methods have been developed, there is a lack of experimental data and comparative studies for actual ship structure details. This study addresses this limitation by evaluating the fatigue strength of longi-web connections in hull structures using local stress approaches, including hot spot stress, effective notch stress, notch stress intensity factor, and structural stress methods. Finite element analyses were conducted, and the predicted fatigue lives and failure locations were compared with experimental results. Although there are some differences between each method, all methods are valid and reasonable for predicting the primary failure locations and evaluating fatigue life. These findings provide a basis for considering suitable fatigue assessment methods for welded ship structures with respect to joint geometry and failure mechanisms. Full article

This story began half a century ago with the discovery of an unusually high presence of tryptophan (Trp, W) in transthyretin (TTR), one of the three carrier proteins of thyroid hormones. With the Trp-rich retinol-binding protein (RBP), TTR forms a plasma complex implicated in the delivery of retinoid compounds to body tissues. W has the lowest concentration among all AAs involved in the sequencing of human body proteins. The present review proposes molecular maps focusing on the ratio of W/AA residues found in the sequence of proteins involved in immune events, allowing us to ascribe the guidance of inflammatory processes as fully under the influence of W. Under the control of cytokine stimulation, plasma biomarkers of protein nutritional status work in concert with major acute-phase reactants (APRs) and with carrier proteins to release, in a free and active form, their W and hormonal ligands, interacting to generate hot spots affecting the course of acute stress disorders. The prognostic inflammatory and nutritional index (PINI) scoring formula contributes to identifying the respective roles played by each of the components prevailing during the progression of the disease. Glucagon demonstrates ambivalent properties, remaining passive under steady-state conditions while displaying stronger effects after cytokine activation. In developing countries, inappropriate weaning periods lead to toddlers eating W-deficient cereals as a staple, causing a dramatic reduction in the levels of W-rich biomarkers in plasma, constituting a novel nutritional deficiency at the global scale. Appropriate counseling should be set up using W implementations to cover the weaning period and extended until school age. In adult and elderly subjects, the helpful immune protections provided by W may be hindered by the surge in harmful catabolites with the occurrence of chronic complications, which can have a significant public health impact but lack the uncontrolled surges in PINI observed in young infants and teenagers. Biomarkers of neurodegenerative and neoplastic disorders measured in elderly patients indicate the slow-moving elevation of APRs due to rampant degradation processes. Full article

While the explosive growth in e-commerce stresses urban logistics systems, city planners lack of fine-grained data in order to anticipate and manage the resulting freight flows. Using a three-stage analytical approach combining descriptive zonal statistics, hotspot analysis and different regression modeling from univariate to geographically weighted regression, this study integrates one year of parcel deliveries from a leading courier with open spatial layers of land-use zoning, census population, mobile-signal activity and household income to model last-mile demand across different land use types. A baseline linear regression shows that residential population alone accounts for roughly 30% of the variance in annual parcel volumes (2.5–3.0 deliveries per resident) while adding daytime workforce and income increases the prediction accuracy to 39%. In a similar approach where coefficients vary geographically with Geographically Weighted Regression to capture the local heterogeneity achieves a significant raise of the overall R² to 0.54 and surpassing 0.70 in residential and institutional districts. Hot-spot analysis reveals a highly fragmented pattern where fewer than 5% of blocks generate more than 8.5% of all deliveries with no apparent correlation to the broaden land-use classes. Commercial and administrative areas exhibit the greatest intensity (1149 deliveries per ha) yet remain the hardest to explain (global R² = 0.21) underscoring the importance of additional variables such as retail mix, street-network design and tourism flows. Through this approach, the calibrated models can be used to predict city-wide last-mile demand using only public inputs and offers a transferable, privacy-preserving template for evidence-based freight planning. By pinpointing the location and the land uses where demand concentrates, it supports targeted interventions such as micro-depots, locker allocation and dynamic curb-space management towards more sustainable and resilient urban-logistics networks. Full article

Based on the engineering background of a new type of segmental-assembled steel temporary beam buttress, the fatigue strength evaluation method of the steel box girders with open longitudinal ribs was taken as the research objective. The fatigue stress calculation analysis and the full-scale fatigue loading test for the steel box girder local component were carried out. The accuracy of the finite-element model was verified by comparing it with the test results, and the rationality of the fatigue strength evaluation methods for welded joints was deeply explored. The results indicate that the maximum nominal stress occurs at the weld toe between the transverse diaphragm and the top plate at the edge of the loading area, which is the fatigue-vulnerable location for the steel box girder local components. The initial static-load stresses at each measuring point were in good agreement with the finite-element calculation results. However, the static-load stress at the measuring point in the fatigue-vulnerable position shows a certain decrease with the increase in the number of cyclic loads, while the stress at other measuring points remains basically unchanged. According to the finite-element model, the fatigue strengths obtained by the nominal stress method and the hot-spot stress method are 72.1 MPa and 93.8 MPa, respectively. It is reasonable to use the nominal stress S-N curve with a fatigue life of 2 million cycles at 70 MPa and the hot-spot stress S-N curve with a fatigue life of 2 million cycles at 90 MPa (FAT90) to evaluate the fatigue of the welded joints in steel box girders with open longitudinal ribs. According to the equivalent structural stress method, the fatigue strength corresponding to 2 million cycles is 94.1 MPa, which is slightly lower than the result corresponding to the main S-N curve but within the range of the standard deviation curve. The research results of this article can provide important guidance for the anti-fatigue design of welded joints in steel box girders with open longitudinal ribs. Full article

As terrestrial resources become increasingly scarce, the exploration and utilization of marine resources have become crucial for ensuring a stable resource supply. A maritime A-Frame is a specialized lifting mechanism mounted on the stern of a vessel, designed for deploying and retrieving heavy loads during subsea exploration. Real-time monitoring of the stress of A-Frames is essential for identifying potential failures and preventing accidents. This paper presents a stress-monitoring campaign conducted on a maritime A-Frame during a deep-sea mining project in the South China Sea. Fiber Bragg Grating (FBG) strain sensors were installed on the A-Frame to measure its stress responses throughout the deep-sea mining operation. The stress variations observed during the deployment and retrieval of a deep-sea mining vehicle were analyzed. The results indicate that the stress caused by the swinging motion of the A-Frame was significantly higher than that generated by the lifting and deployment of the mining equipment. Additionally, a finite element model (FEM) of the A-Frame was developed to estimate the stress of the hot spots by integrating the measured strain data. The analysis confirmed that the maximum stress experienced by the A-Frame was well below the allowable threshold, indicating that the structure had sufficient strength to withstand operational loads. In addition, the swing angle of the A-Frame significantly affects the stress value of the A-Frame, while lifting the mining vehicle has a very slight effect. Thus, it is advisable to accelerate the deployment and retrieval speeds of the mining vehicle and minimize the outward swing angle of the A-Frame. These findings provide valuable insights for optimizing the design and ensuring the safe operation of maritime A-Frames in deep-sea mining exploration. Full article

Enhanced abiotic stresses such as increased drought, elevated temperatures, salinity, and extreme weather phenomena severely affect major crops in the Mediterranean area, a ‘hot spot’ of climate change. Plants have evolved mechanisms to face stressful conditions and adapt to increased environmental pressures. Intricate molecular processes involving genetic and epigenetic factors and plant–microbe interactions have been implicated in the response and tolerance to abiotic stress. Deciphering the molecular mechanisms whereby plants perceive and respond to stress is crucial for developing strategies to counteract climate challenges. Progress in determining genes, complex gene networks, and biochemical pathways, as well as plant–microbiota crosstalk, involved in abiotic stress tolerance has been achieved through the application of molecular tools in diverse genetic resources. This knowledge could be particularly useful for accelerating plant improvement and generating resilient varieties, especially concerning woody perennial crops, where classical breeding is a lengthy and labor-intensive process. Similarly, understanding the mechanisms of plant–microbe interactions could provide insights into innovative approaches to facing stressful conditions. In this review, we provide a comprehensive overview and discuss the recent findings concerning the genetic, epigenetic, and microbial aspects shaping abiotic stress responses, in the context of enhancing resilience in important Mediterranean woody perennial fruit crops. Full article

Tubular structures are critical in renewable energy and offshore industries but face significant loads over time, leading to joint degradation. Carbon fiber-reinforced polymers (CFRPs) offer promising rehabilitation solutions, yet existing studies often overlook stress concentration factors (SCFs) along the weld toe. This study examines SCFs at 24 weld toe positions in CFRP-reinforced KT-joints under axial compression. Using 5429 simulations and artificial neural networks, precise estimations of CFRPs’ impact on SCFs were achieved, with <10% error. These findings demonstrate CFRPs’ potential to reduce SCFs and improve fatigue life prediction for tubular joints under axial compression. Full article

Rib–deck (RD) welded joints in orthotropic steel bridge decks are prone to different fatigue crack mechanisms. Standard fatigue design methods are inadequate for some of these mechanisms under multiaxial non-proportional loading conditions. This study presents a framework to assess fatigue damage at RD welded joints, considering the different crack mechanisms based on the equivalent structural stress method and its extension to multiaxial non-proportional fatigue, which is the path-dependent maximum stress range (PDMR) cycle counting algorithm. The method is validated for uniaxial loading by using experimental data from the literature. Additionally, non-proportional fatigue damage at RD welded joints of a suspension bridge girder is investigated under simulated random traffic loading. The analyses reveal the limitations of the nominal stress approach to account for complex stress field variations. The PDMR method, more suited to capture the stress path dependency of non-proportional fatigue damage than the hot spot and critical plane-based methods, predicts higher fatigue damage. A comprehensive fatigue test campaign of full-scale RD welded joints is necessary to better understand their fatigue behaviour under multiaxial loading. Until more experimental data are available, the PDMR method is recommended for fatigue verifications of welded RD joints as it yields safer predictions. Full article

A CHS-to-CFRHS Y-joint that consists of a circular hollow section (CHS) brace and a concrete-filled rectangular hollow section (CFRHS) chord by welding has a simple and smooth weld profile that saves time and cost for the fabrication of CHS-to-CFRHS Y-joints and leads to a superior fatigue performance, compared with other welded tubular joints. This investigation presented an analysis of the stress concentration factors (SCFs) of CHS-to-CFRHS Y-joints subjected to axial tension loading of the brace. First, a finite element (FE) modelling method, which was validated with the experimental results cited in the reference, was utilised to establish the FE models of CHS-to-CFRHS Y-joints. Then, a parametric analysis was conducted to investigate the influences of the significant non-dimensional geometric parameters on the SCFs of CHS-to-CFRHS Y-joints. It is found that the intersection angle of the brace and chord has an important influence on the magnitudes of the SCF values. An increase in the intersection angle of the brace and chord will increase the values of the SCFs at the 60° location and saddle. The values of the SCFs at the 60° location and saddle reach the maximum value when the intersection angle of the brace and chord reaches 90°. Furthermore, on the basis of the large database of the SCF results, empirical design equations were established to calculate the SCFs at the crown toe, 60° location and saddle via multiple regression analysis. A safety factor was applied to the empirical design equations to ensure safe and reliable results of SCF calculations for the fatigue design of CHS-to-CFRHS Y-joints in a composite truss structure. Ultimately, a comparative analysis of SCFs was conducted with the FE models of welded tubular joints with rectangular hollow section (RHS) chords and CFRHS chords. The results reveal that infilling concrete in the chord leads to a reduction in SCFs along the weld profile of more than 11% on average, and the peak SCF decreases by more than 15%. Full article

There is no doubt that global climate change is happening and affecting life on Earth in a variety of ways. It can be seen on the extreme events of natural disasters, prolonged periods of drought, and increased summer and annual temperatures. While climate change affects every place on Earth, the Mediterranean region is considered a hot spot of climate change. Temperature is expected to increase further, precipitation, especially during summer months, is expected to decrease, and extreme rainfall events are projected to increase. These projected changes will affect both continental and insular environments, with small islands being particularly vulnerable due to the lack of space for species to move into more favorable conditions. As a result, these environments need to be studied, the changes quantified, and the consequences monitored. The current study focuses on the island of Fournoi in the central eastern part of the Aegean Sea. We employed data from a local meteorological station, which operates for a limited period, the Climate Research Unit TS data, and remote sensing thermal data to monitor the trends in aridity over a period of almost 40 years. The results show that summer temperature has increased significantly over the last 40 years, and this is confirmed by both meteorological and remote sensing data. At the same time, precipitation seems to remain stable. Despite the increased aridity imposed by the increased temperature and stable precipitation, vegetation seems not to be experiencing extreme stress. On the contrary, it seems to be following a positive trend over the study period. This observation is explained by the extreme resilience of the plant species of the study area and the fact that vegetation has been recovering over the last 50 years after a period of human overexploitation, and this recovery overcomes the stress imposed by increased aridity. Full article

The thermal chemical vapor deposition (CVD) process was utilized to fabricate 6H-structured SiC coating dies with carbon control. The carbon-rich clusters along the SiC grain boundaries acted as a pinning site to suppress irregular crystal growth and to homogenize the fine-grained structure. These massive carbon-supersaturated (MCSed) SiC dies with a thickness of 4 mm were utilized for upsetting pure titanium bars in dry and cold conditions. Under a stress gradient from the contact interface to the depth of the SiC coating, the carbon solute isolated from these carbon clusters diffused through the grain boundaries and formed free carbon agglomerates on the contact interface to the pure titanium bars. These in situ-formed free carbon agglomerates acted as a solid lubricant to sustain the friction coefficient at 0.09 at the hot spots on the contact interface and to protect the dies and bars from severe adhesive wearing. Full article

This experimental study delves into the intricate mechanics of stress concentration and fatigue behavior exhibited by 9% Ni steel welded joints under cryogenic conditions. The study specifically examines butt-welded, fillet longitudinal, and fillet transverse specimens, comparing their fatigue properties under room and cryogenic temperatures. Notably, determining hot-spot stress presents a challenge, as it cannot be directly obtained through traditional means. To overcome this limitation, a method for predicting hot-spot stress is introduced, which considers the effects of misalignments and weld bead characteristics. The study also highlights the impact of grip-clamping-induced specimen deformation and the reduced middle section on stress concentration resulting from misalignments. Furthermore, it proposes separate consideration of the effects of the weld bead on the axial nominal stress and on the bending stress of the specimen. The accuracy of strain gauge measurements in cryogenic environments is addressed by suggesting a method to correct the output of 2-wire strain gauges using a fixed ratio derived from 2-wire and 3-wire strain gauges. By comparing predicted hot-spot stress with actual measurements, the study validates the reliability of the proposed predictive method. These findings contribute to a deeper understanding of the behavior of 9% Ni steel welded joints under cryogenic conditions and provide valuable insights for design and engineering in similar applications. Full article

The 9p21.3 genomic locus is a hot spot for disease-associated single-nucleotide polymorphisms (SNPs), and its strongest associations are with coronary artery disease (CAD). The disease-associated SNPs are located within the sequence of a long noncoding RNA ANRIL, which potentially contributes to atherogenesis by regulating vascular cell stress and proliferation, but also affects pancreatic β-cell proliferation. Altered expression of a neighboring gene, CDKN2B, has been also recognized to correlate with obesity and hepatic steatosis in people carrying the risk SNPs. In the present study, we investigated the impact of 9p21.3 on obesity accompanied by hyperlipidemia in mice carrying a deletion of the murine ortholog for the 9p21.3 (Chr4^Δ70/Δ70) risk locus in hyperlipidemic Ldlr^−/−ApoB^100/100 background. The Chr4^Δ70/Δ70 mice showed decreased mRNA expression of insulin receptors in white adipose tissue already at a young age, which developed into insulin resistance and obesity by aging. In addition, the Sirt1-Ppargc1a-Ucp2 pathway was downregulated together with the expression of Cdkn2b, specifically in the white adipose tissue in Chr4^Δ70/Δ70 mice. These results suggest that the 9p21.3 locus, ANRIL lncRNA, and their murine orthologues may regulate the key energy metabolism pathways in a white adipose tissue-specific manner in the presence of hypercholesterolemia, thus contributing to the pathogenesis of metabolic syndrome. Full article

Temperature is a critical parameter for the GaN HEMT as it sharply impacts the electrical characteristics of the device more than for SiC or Si MOSFETs. Either when designing a power converter or testing a device for reliability and robustness characterizations, it is essential to estimate the junction temperature of the device. For this aim, manufacturers provide compact models to simulate the device in SPICE-based simulators. These models provide the junction temperature, which is considered uniform along the channel. We demonstrate through two-dimensional numerical simulations that this approach is not suitable when the device undergoes high electrothermal stress, such as during short circuit (SC), when the temperature distribution along the channel is strongly not uniform. Based on numerical simulations and experimental measurements on a 650 V/4 A GaN HEMT, we derived a thermal network suitable for SPICE simulations to correctly compute the junction temperature and the SC current, even if not providing information about the possible failure of the device due to the formation of a local hot spot. For this reason, we used a second thermal network to estimate the maximum temperature reached inside the device, whose results are in good agreement with the experimental observed failures. Full article

The study aims to investigate the impact of uniform, grooving and non-uniform corrosion degradation on the hot-spot stresses of a T-shaped tubular joint using the finite element method. The through-thickness linearization method is employed to estimate the hot-spot stresses, allowing a more reasonable consideration of the effect of grooving corrosion and non-unform corrosion. The grooving corrosion degradation is modelled assuming that the corrosion rate of the weld metal is 1.4 times that of the base metal. The non-uniform corrosion is modelled by moving the nodes around the weld by a random distance along the direction perpendicular to the surface. The random distances are generated based on the surface roughness parameter Ra. The results indicate that the stress concentration factor (SCF) increases with the uniform corrosion depth. The grooving corroded tubular joint results in a higher SCF than those of the corresponding uniformly corroded tubular joint. The non-uniform corrosion can lead to SCF deviations from the SCF of the uniformly corroded tubular joint. The SCF deviation at the critical region follows the normal distribution, and its standard deviation increases with Ra. Full article