Search Results (200)

Suspension dome structures are widely utilized due to their superior performance compared to conventional structures. The condition of the cables, particularly the forces they experience, is critical for ensuring the safety of the overall structures. However, friction between cables and joints significantly disrupts cable force distribution, particularly during pre-stressing construction. This paper integrates a tension-compensation method with a numerical approach that accurately accounts for friction effects. A computational flowchart was introduced and subsequently applied to analyze a practical suspension dome structure. We assessed the impact of friction on cable forces, structural deformations, and the mechanical state of the cable–strut system. Furthermore, we quantified the consequences of excessive tensioning. The findings demonstrate that the method presented in this paper can efficiently be employed for the analysis of large-scale complex structures and is readily accessible to structural designers. Full article

Clouds modulate the net radiative flux that interacts with both shortwave (SW) and longwave (LW) radiation, but the uncertainties regarding their effect in polar regions are especially high because ground observations are lacking and evaluation through satellites is made difficult by high surface reflectance. In this work, sky conditions for six different polar stations, two in the Arctic (Ny-Ålesund and Utqiagvik [formerly Barrow]) and four in Antarctica (Neumayer, Syowa, South Pole, and Dome C) will be presented, considering the decade between 2010 and 2020. Measurements of broadband SW and LW radiation components (both downwelling and upwelling) are collected within the frame of the Baseline Surface Radiation Network (BSRN). Sky conditions—categorized as clear sky, cloudy, or overcast—were determined using cloud fraction estimates obtained through the RADFLUX method, which integrates shortwave (SW) and longwave (LW) radiative fluxes. RADFLUX was applied with daily fitting for all BSRN stations, producing two cloud fraction values: one derived from shortwave downward (SWD) measurements and the other from longwave downward (LWD) measurements. The variation in cloud fraction used to classify conditions from clear sky to overcast appeared consistent and reasonable when compared to seasonal changes in shortwave downward (SWD) and diffuse radiation (DIF), as well as longwave downward (LWD) and longwave upward (LWU) fluxes. These classifications served as labels for a machine learning-based classification task. Three algorithms were evaluated: Random Forest, K-Nearest Neighbors (KNN), and XGBoost. Input features include downward LW radiation, solar zenith angle, surface air temperature ($T_a$), relative humidity, and the ratio of water vapor pressure to $T_a$. Among these models, XGBoost achieved the highest balanced accuracy, with the best scores of 0.78 at Ny-Ålesund (Arctic) and 0.78 at Syowa (Antarctica). The evaluation employed a leave-one-year-out approach to ensure robust temporal validation. Finally, the results from cross-station models highlighted the need for deeper investigation, particularly through clustering stations with similar environmental and climatic characteristics to improve generalization and transferability across locations. Additionally, the use of feature normalization strategies proved effective in reducing inter-station variability and promoting more stable model performance across diverse settings. Full article

Background: Liver cancer is a major health concern worldwide. Radiofrequency ablation is a safe treatment option that can be guided by either ultrasound, computer tomography (CT), or fluoroscopy. Although ultrasound-guided radiofrequency ablation is commonly used in clinical practice, radiofrequency ablation guided by CT is more precise but requires more time and does not offer real-time monitoring, which may result in complications such as pneumothorax or organ damage. Objectives: In this study, we investigated the effect of ultrasound, CT, and combined ultrasound/CT guidance on patient survival and complication development. Methods: A total of 982 radiofrequency ablation sessions conducted on 553 patients were analyzed. Clinical outcomes were assessed during follow-up to determine the survival and recurrence rates of malignant tumors. Results: Overall, the three guidance approaches exhibited significant differences in terms of tumor size, number, complication development, and treatment duration. However, no significant differences were observed in survival rate. A comparison of the effect of CT guidance and ultrasound guidance on complication development revealed a higher odds ratio for CT guidance in some cases. A comparison of combined ultrasound/CT guidance and ultrasound guidance revealed nonsignificant differences in complication development. A comparison of CT guidance and combined ultrasound/CT guidance revealed a higher odds ratio for CT guidance in some cases. Radiofrequency ablation is a safe and effective treatment for liver tumors. However, CT has an increased incidence of complications. Conclusions: Combined ultrasound/computer tomography guidance is recommended for patients with multiple or large tumors or tumors near the hepatic dome or diaphragm. Full article

Type IV composite overwrapped pressure vessels (COPVs) store hydrogen at pressures up to 70 MPa and must meet stringent safety standards through physical testing. However, full-scale burst, plug torque, axial compression, impact, and drop tests are time-consuming and costly. This study proposes a unified finite element analysis (FEA) workflow that replicates these mandatory tests and predicts failure behavior without physical prototypes. Axisymmetric and three-dimensional solid models with reduced-integration elements were constructed for the polyamide liner, aluminum boss, and carbon/epoxy composite. Burst simulations showed that increasing the hoop-to-axial stiffness ratio shifts peak stress to the cylindrical region, promoting a longitudinal rupture—considered structurally safer. Plug torque and axial load simulations revealed critical stresses at the boss–composite interface, which can be reduced through neck boss shaping and layup optimization. A localized impact with a 25 mm sphere generated significantly higher stress than a larger 180 mm impactor under equal energy. Drop tests confirmed that 45° oblique drops cause the most severe dome stresses due to thin walls and the lack of hoop support. The proposed workflow enables early-stage structural validation, supports cost-effective design optimization, and accelerates the development of safe hydrogen storage systems for automotive and aerospace applications. Full article

Pressure relief devices are critical for the safe release of pressurized hydrogen. To address the risk of spontaneous ignition during a high-pressure release, three-dimensional (3D) numerical simulations are systematically conducted to investigate the effects of burst conditions on spontaneous ignition behavior. Eight simulation cases are considered, involving two opening processes (instantaneous and 10-step-like), three burst disk shapes (flat, conventional domed, and reverse domed), and five opening ratios (1, 0.8, 0.6, 0.4, and 0.2). The 10-step-like opening enhances jet turbulence and promotes flame merging between the boundary layer and jet front, intensifying combustion. Domed structures cause a high-velocity region behind the leading shock wave, altering jet front evolution. Compared with reverse-domed disks, flat and conventional domed disks generate stronger vortices and a larger shock-heated area, resulting in more severe combustion and elevated fire risk. As the opening ratio decreases, both shock wave strength and propagation velocity drop significantly, and spontaneous ignition does not occur. The opening ratio has minimal influence on the distance traveled by shock-induced heating. These findings offer meaningful guidance for the design and manufacture of pressure relief devices for the safe emergency release of hydrogen. Full article

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

The biologic response following the insertion of dental implants is a widely studied process. Recent research has highlighted the importance of implant surface topography and chemistry as highly influential factors in consolidating the dental implant with the surrounding biological environment. The hydrophilicity, or wettability, of dental implants plays a pivotal role in these interactions and successful osseointegration. A more well-established factor that can also influence the development of the tissue–implant interface is exposure to tobacco smoke. While the negative impact of smoking on the biological response of the tissue is clear, there has been no research evaluating the impact that tobacco smoke can have directly on the surface chemistry of dental implants. The present study aimed to explore the effect of smoking on implant surface chemistry and wettability in vitro. Five different implant disks (Ti-Mach, Ti-SLA, Ti-Alloy, Zirc-1 and Zirc-2) were subjected to contamination with tobacco smoke using a portable smoke infuser with dome enclosure. Occasional smoking (5×/day 10 min each for 3 days) and heavy smoking (20×/day for 10 min each for 10 days) were simulated. The wettability of the implant disks was evaluated via the contact angle technique using artificial blood and albumin, as well as saline as a control. It was determined that the contamination of implant surfaces due to smoking produces changes in the surface chemistry and wettability. Changes in the surface hydrophilicity differed based on the implant material. Within the constraints of this investigation, tobacco smoke improved the hydrophilicity of titanium surfaces but worsened that of ceramic surfaces when utilizing the testing solutions. Different implant surfaces exhibit different wetting behavior following contamination with nicotine smoke. This might have an impact on the treatment of peri-implantitis in smokers due to changes in implant surface hydrophilicity, which can affect the re-osseointegration process. Full article

The aim of this research is the structural study of the dome of Tesoro di San Gennaro in Naples compared with the more recent studies about San Francesco di Paola, as examples, respectively, of baroque and neoclassic style, emblems of different stylistic periods of Neapolitan architectural schools about domes and churches. The studies are carried out with particular attention to evaluating their seismic safety without considering the role of the vertical supporting structures. The analysis adopts graphical approaches to assess the safety of the two domes under vertical and horizontal loads, with a special focus on the effects of earthquakes. In the case of San Gennaro, the approach is mixed between the rigid-kinematic theory and the theory of elasticity due to the presence of a wooden structure, while in the case of San Francesco di Paola, only the thrust-line method was used, applying it to the three-dimensional structures through the slicing technique. In conclusion, the methods to assess the safety of the domes under both vertical and horizontal seismic loads allow for a comparison of the two structures and provide a comprehensive evaluation of their structural integrity. The study demonstrates, through a predominantly graphical methodology, the effectiveness of traditional equilibrium-based approaches in assessing dome stability, highlighting the active contribution of the timber structure in San Gennaro and quantifying its role under seismic loading scenarios. Full article

This research introduces an innovative probabilistic method for examining torsional stress behavior in spherical shell structures through Monte Carlo simulation techniques. The spherical geometry of these components creates distinctive computational difficulties for conventional analytical and deterministic numerical approaches when solving torsion-related problems. The authors develop a comprehensive mesh-free Monte Carlo framework built upon the Feynman–Kac formula, which maintains the geometric symmetry of the domain while offering a probabilistic solution representation via stochastic processes on spherical surfaces. The technique models Brownian motion paths on spherical surfaces using the Euler–Maruyama numerical scheme, converting the Saint-Venant torsion equation into a problem of stochastic integration. The computational implementation utilizes the Fibonacci sphere technique for achieving uniform point placement, employs adaptive time-stepping strategies to address pole singularities, and incorporates efficient algorithms for boundary identification. This symmetry-maintaining approach circumvents the mesh generation complications inherent in finite element and finite difference techniques, which typically compromise the problem’s natural symmetry, while delivering comparable precision. Performance evaluations reveal nearly linear parallel computational scaling across up to eight processing cores with efficiency rates above 70%, making the method well-suited for multi-core computational platforms. The approach demonstrates particular effectiveness in analyzing torsional stress patterns in thin-walled spherical components under both symmetric and asymmetric boundary scenarios, where traditional grid-based methods encounter discretization and convergence difficulties. The findings offer valuable practical recommendations for material specification and structural design enhancement, especially relevant for pressure vessel and dome structure applications experiencing torsional loads. However, the probabilistic characteristics of the method create statistical uncertainty that requires cautious result interpretation, and computational expenses may surpass those of deterministic approaches for less complex geometries. Engineering analysis of the outcomes provides actionable recommendations for optimizing material utilization and maintaining structural reliability under torsional loading conditions. Full article

Introduction: The anatomy of the distal tibiofibular joint (DTFJ) has been demonstrated to influence the radiological outcome of reduction with syndesmotic screw fixation in the course of ankle fracture treatment. The objective of this study was to describe the anatomy of the DTFJ and to analyze the effect of incisura anatomy on syndesmotic stabilization with suture button systems (SBS), also in the context of their flexible nature of fixation. Materials and Methods: Forty-four (21 females, 23 males) consecutive postoperative bilateral computed tomography scans after stabilization of the DTFJ by SBS in the course of operative treatment of unstable ankle fractures were retrospectively analyzed. The anatomy of the DTFJ was evaluated by examining the following parameters: depth of the tibial incisura (DI), rotation of the incisura (ROI), Nault talar dome angle (NTDA), Leporjärvi clear space (LCS), anterior tibiofibular distance (antTFD), and fibula engagement (FE). The side-to-side (Δ) of LCS, NTDA, and antTFD, which analyzed the reduction result, were correlated with DI, FE, ROI, and NTDA, as well as the transverse offset (TO), reflecting the flexible nature of fixation. Results: Patients with slight overtightening (ΔLCS > −1 mm) showed a fibula that protruded less into the incisura on the native side (smaller FE) compared to symmetrical reduced patients and to patients with slight diastasis (p < 0.05). There was no relationship between the parameters describing the anatomy of the incisura and parameters assessing the parameter of the “flexible nature of fixation” (rs < 0.300). Regarding the anatomical parameters, it was observed that there were inter-individual differences of more than 4 mm (p > 0.05). Conclusions: The considerable inter-individual anatomical variability of the DTFJ was confirmed. The morphological configuration of the incisura has no impact on the immediate radiological reduction result after SBS stabilization of the DTFG, as determined by CT. The extent of the flexible nature of fixation is also not affected by the morphology of the incisura. Stabilization of the DTFJ can be performed regardless of the anatomical configuration. Full article

With the intensifying global energy crisis, ensuring robust and reliable energy reserves has become crucial, and underground energy storage offers a safe, large-scale, and cost-effective solution. Among various options, salt cavern gas storage is recognized for its excellent sealing capacity and geological stability; however, many natural salt domes contain inherent fissures and interlayers (e.g., gypsum) that can jeopardize operational safety. Hence, this study aims to clarify how different fissure angles and bedding plane dip angles affect the mechanical behavior of salt–gypsum composites, providing insights for enhancing safety measures in underground gas storage facilities. Based on practical engineering demands, we employ finite element software (RFPA2.0) under a confining pressure of 25 MPa to investigate the compressive strength, fractur patterns, and acoustic emission responses of salt–gypsum composites with varying bedding plane and fissure angles. The results indicate that (1) the composite’s compressive strength gradually increases with the fissure angle, being lowest at 0° and highest at 90°; (2) as the bedding plane angle increases, the compressive strength first rises, then decreases, and finally rises again, with its minimum at 60° and maximum at 90°; and (3) when the bedding plane angle exceeds 60°, cracks preferentially develop along the bedding plane, dominating the overall fracture process. These findings provide theoretical guidance for optimizing the design and ensuring the long-term safety and stability of underground salt cavern gas storage systems. Full article

While L-PBF research continuously expands technologically towards more complex-shaped components and effective scanning strategies, the customization of the mechanical performance of these components to specific applications is still challenging. The presence of high process-induced residual stress levels frequently makes the current (standard) mechanical testing procedures ineffective or even inappropriate. The current engineering design principles cannot be applied to L-PBF components as the available mechanical properties are apparent (i.e., space and residual stress dependent properties). It is the aim of this work to overcome the aforementioned limitations by presenting a comprehensive methodology that can be used to determine the mechanical performance of an L-PBF 316L deposit along (five) pre-specified directions, denoted as performance lines (PLs), and in six special key regions, denoted as performance zones (PZs), through the nanoindentation test (PL-nIIT). The PLs determine the gradients of the indentation properties across the deposit, while the PZs exhibit the orientation-dependent mechanical performance in a specified number of regions of the deposit. The latter can be used for benchmarking, mechanical design, or performance customization. The frequently resorted to indentation modulus and hardness have thus been complemented with a new indentation size effect-free property (i.e., the loading stiffness rate, LSR) to help discriminate the presence of residual stress at different depths in the given deposit. A decreasing mild compressive residual stress was determined along the build direction of the deposit as revealed by the decreasing values of the relative LSR, H_IT, and E_IT (from the root to the top dome, i.e., 47.8 to 43.4, 2.57 to 2.49, and 216 to 202 GPa, respectively). Full article

The global challenge of food waste management poses severe environmental and public health risks. Traditional disposal methods, such as landfilling and incineration, exacerbate these issues. Decomposing food waste in landfills emits methane, a greenhouse gas 25 times more potent than CO₂, while landfill leachate contaminates soil and groundwater with hazardous pathogens and toxins. Additionally, improper waste disposal fosters microbial proliferation, posing severe health risks. Incineration, though commonly used, is inefficient due to the high moisture content of food waste, leading to incomplete combustion and further air pollution. Therefore, this review examines biodigesters as a sustainable alternative to traditional food waste disposal, assessing their effectiveness in mitigating environmental and health risks while promoting circular economy practices. It evaluates different biodigester designs, their operational scalability, and their economic feasibility across diverse global contexts. Through an analysis of case studies, this review highlights biodigesters’ potential to address localized waste management challenges by converting organic waste into biogas—a renewable energy source—and nutrient-rich digestate, a valuable natural fertilizer. The process reduces greenhouse gas emissions, improves soil health, and minimizes public health risks associated with microbial contamination. Various biodigester designs, including fixed-dome, floating-drum, and tubular systems, are compared for their efficiency and adaptability. Additionally, this review identifies key barriers to biodigester adoption, including feedstock variability, maintenance costs, and policy constraints, while also discussing strategies to enhance their efficiency and accessibility. This review is novel in its comprehensive approach, bridging the technological, environmental, and public health perspectives on biodigesters in food waste management. Unlike prior studies that focused on isolated aspects—such as specific case studies, policy analyses, or laboratory-scale evaluations—this review synthesizes the findings across diverse real-world implementations, offering a holistic understanding of biodigesters’ impact. By addressing knowledge gaps in terms of health risks, environmental benefits, and economic challenges, this study provides valuable insights for policymakers, researchers, and industry stakeholders seeking sustainable waste management solutions. Full article

A reverse-flow combustor has a larger liner surface area due to airflow turning, which complicates flow and cooling control, particularly heat transfer efficiency. Effective heat management is essential for maintaining uniform temperature distribution and preventing thermal gradients. This study explores the impact of axial position and diameter of primary holes on thermal performance and flow dynamics. Results indicate that as the primary holes move toward the dome, the recirculation vortex size decreases, leading to insufficient fuel mixing, a reduction in the high-temperature area in the primary zone, and an increase in the high-temperature area of the middle zone. On the other hand, moving the primary holes downstream enhances fuel mixing, increasing high-temperature areas in the primary zone and reducing them in the middle and dilution zones, thus improving thermal boundary layers and convective heat transfer rates. When the primary hole is moved 10 mm downstream, outlet temperature improves significantly with an outlet temperature distribution factor (OTDF) of 0.21 and a radial temperature distribution factor (RTDF) of 0.16. Additionally, reducing the upper primary hole diameter strengthens jet deflection, improving fuel–gas mixing at the dome and heat transfer to the central region. With a 2.1 mm hole diameter, the temperature gradient decreases, resulting in an OTDF of 0.184 and RTDF of 0.15. Furthermore, as the momentum flux ratio increases, the jet penetration depth initially rises and then stabilizes. Momentum flux ratios between 10.6 and 15.1 significantly affect jet penetration, while further increases result in smaller fluctuations. Higher momentum flux ratios create localized high- and low-temperature zones, reducing outlet temperature distribution quality. The optimal momentum ratio for the reverse-flow combustor, ensuring effective jet penetration and better temperature distribution, is between 10.6 and 14.7, with a corresponding penetration depth of 34.3 mm to 35.1 mm. These findings offer valuable insights for improving reverse-flow combustor design and performance. Full article

Mental imagery influences the body, movement, and technical skills of the dancer. The aim of this study was to identify the influence of dance imagery on the electromyographic parameters of selected muscles in a professional ballet dancer during three ballet tasks: parallel position, demi pointe relevé, and demi plié. Five mental imageries according to the Franklin Method^® were used: foot dome, the wheelbarrow, pushing the toes, space behind the kneecap, and the kneecap float. Electromyographic signals were recorded bilaterally for lumbar erector spinae, rectus abdominis, vastus medialis, long head of biceps femoris, lateral head of gastrocnemius, tibialis anterior, and fibularis longus. All of the mental imageries resulted in increased activity (above 20% compared with no-imagery performance) of the selected muscles in the studied classical dance positions and tasks. Overall, the ankle muscles were influenced the most. This study indicates that mental images effectively influence a physiological parameter, as indicated by an electromyographic signal. Full article