Search Results (3,037)

This study investigates the effects and mechanisms of high-power microwave on GaN HEMTs. By injecting high-power microwave from the gate into the device and employing techniques such as DC characteristics, gate-lag effect analysis, low-frequency noise measurement, and focused ion beam (FIB) cross-sectional inspection, a systematic investigation was conducted on GaN HEMT degradation and failure behaviors under conditions of a low duty cycle and narrow pulse width. Experimental results indicate that under relatively low-power HPM stress, GaN HEMT exhibits only a slight threshold voltage shift and a modest increase in transconductance, attributed to the passivation of donor-like defects near the gate. However, when the injected power exceeds 43 dBm, the electric field beneath the gate triggers avalanche breakdown, forming a leakage path and causing localized heat accumulation, which ultimately leads to permanent device failure. This study reveals the physical failure mechanisms of GaN HEMTs under low-duty-cycle HPM stress and provides important guidance for the reliability design and hardening protection of RF devices. Full article

Background/Objective: Clinical statistics show that bacterial infection is a major driver of implant failure. To enhance antibacterial performance, some metallic elements, such as silver (Ag), zinc (Zn), and copper (Cu), are commonly used to modify the titanium surface. Despite the promising antibacterial performance of Ag, concerns persist regarding dose-dependent cytotoxicity, systemic accumulation, and potential effects on local bone metabolism. This review aimed to investigate the effects of incorporating or coating titanium (Ti) implant surfaces with Ag on bone formation around implants. Methods: A search was undertaken using three main databases (PubMed, Web of Science, and Scopus). The search was limited to studies published within the last 20 years that involved animal experiments using endosseous implants coated with or incorporating Ag. Meta-analyses were performed for bone-to-implant contact (BIC), bone formation (BA), and bone volume (BV/TV) around the implant in control and test groups. The compared groups were subjected to similar implant surface treatments aside from the presence of silver in the test group. Results: Sixteen studies met the inclusion criteria in this study and were included. The analysis of BIC values revealed a statistically significant overall effect in favor of silver-coated implants (Z = 2.01, p = 0.04), along with 95% confidence intervals (CIs). The BA analysis found no significant difference between silver-coated and control implants (Z = 1.09, p = 0.28). The BV/TV analysis also showed no statistically significant overall difference (Z = 0.35, p = 0.73). Conclusions: In animal models, silver-coated Ti implants improve bone–implant contact without altering peri-implant bone volume metrics. Full article

A group of Spanish experts of different specialties participated in the ENFOCA2 project, promoted by the Spanish Oncology Genitourinary Group (SOGUG), which was designed to provide updated information on current and novel aspects contributing to the optimal care of prostate cancer (PCa) patients. In localized disease, it is important to implement strategic alliances with other institutions for improving adherence to active surveillance in low-risk groups and to explore genetic testing for a better indication of focal therapy. Local control of the disease should be maximized to prevent local failure and biochemical recurrence. In patients with locally advanced disease, with PSMA PET/CT-positive lesions in M0 staging on conventional imaging techniques, therapeutic decisions should be carefully evaluated due to insufficient evidence regarding the gold standard in this setting. In patients with metastatic castration-resistant PCa (mCRPC), assessment of BRCA somatic and germline mutations provides prognostic information and familial cancer risk and informs treatment decisions. Combinations of androgen receptor signaling inhibitor (ARSi) agents and poly-ADP ribose polymerase inhibitors (PARPi) are emerging alternatives for advanced PCa. The oldest segment of PCa patients (>70 years of age) may require geriatric assessment to evaluate physical and functional reserves, tailoring treatment to their individual characteristics and circumstances. The concept of a comprehensive multidisciplinary approach together with inter-center and/or inter-specialty therapeutic alliances should be implemented in the routine care of patients with PCa. Full article

Ply Curving Termination (PCT) is an effective method to suppress stress concentration at composite ply drop-offs by locally curving the reinforcing fibers to reduce the stiffness. A previous study by the authors confirmed that PCT can suppress fatigue delamination failure in composite ply drop-off. However, the specimens used were external ply drop-offs without cover plies and did not reflect practical structural configurations. Following the basic study, this current study evaluated the fatigue damage suppression characteristic of PCT in practically relevant internal ply drop-offs with cover plies. Finite element analysis, fatigue testing, and detailed observation of the failure process using X-ray CT showed that PCT is effective in suppressing fatigue failure of internal ply drop-offs. In particular, delamination propagation from matrix cracks along the curving fibers, a weak point of PCT, is suppressed in the external ply drop-off. Finite element analysis indicated the importance of stress transfer from the cover ply to the ply drop-off, confirming that the fatigue damage suppression effect of PCT is enhanced in practical composite ply drop-off configurations. Full article

The biomechanical performance of dental implants is affected by both abutment height and bone quality, which influence stress distribution around the implant and the preservation of surrounding bone. This study used three-dimensional finite element analysis (FEA) to assess the combined effects of these factors. Two implants with abutment heights of 3 mm and 6 mm were modeled and placed in mandibular bone blocks representing class II and class IV bone, according to Lekholm and Zarb’s classification. A static load of 150 N, inclined at 6° buccolingually, was applied during the analysis. The simulation results showed that increasing the abutment height raises stress on the implant, leading to greater stress transfer to the peri-implant bone. The von Mises stress levels were higher in the crestal cortical bone of the class IV model with a 6 mm abutment (126 MPa). Notably, peak stresses exceeding 300 MPa were localized at the implant-abutment connection. These findings suggest that abutment height is a critical factor that negatively affects the biomechanical response, especially in low-density bone, although longer abutments offer biological benefits. This highlights the importance of minimizing the crown-to-implant ratio to reduce overload, preserve bone, and prevent mechanical failure complications. Full article

Although heart transplantation remains the gold standard in the treatment of advanced heart failure, the limited availability of donor organs and the growing number of patients requiring long-term care have necessitated wider implementation of mechanical circulatory support (MCS). Ventricular assist devices (VADs) substantially improve survival and quality of life, yet their clinical use is still constrained by serious complications, most notably local infections at percutaneous exit sites. This challenge persists across all device generations, from extracorporeal pulsatile pumps to contemporary continuous-flow systems. While fourth-generation concepts based on transcutaneous energy transfer are under development, unresolved issues such as thermal tissue injury continue to impede their adoption. This review critically examines current evidence on local infections, with particular emphasis on the role of biomaterials in bacterial colonization. The clinical burden and microbial etiology, dominated by Staphylococcus aureus and Staphylococcus epidermidis, are outlined, together with the limitations of existing material solutions, which lack durable antimicrobial activity. These infections frequently result in tissue necrosis, sepsis, rehospitalization, and elevated treatment costs, and their management is further complicated by the global rise in antimicrobial resistance. By synthesizing available data and identifying key shortcomings of current materials, this review underscores the urgent need for next-generation biomaterials with enhanced biocompatibility, resistance to microbial adhesion, and intrinsic or functionalized antimicrobial activity. Such advances are essential to improve the long-term safety and clinical outcomes of MCS therapy. Full article

The waviness defect, a common manufacturing flaw in composite structures, can significantly impact the mechanical performance. This study investigates the effects of wrinkles on the ultimate load and failure modes of two Carbon Fiber Reinforced Composite (CFRC) laminates through compressive experiments and simulation analyses. The laminates have stacking sequences of [0]_10S and [45/0/−45/90/45/0/−45/0/45/0]_S. Each laminate includes four different waviness ratios (the ratio of wrinkle amplitude to laminate thickness) of 0%, 10%, 20% and 30%. In the simulation, a novel multiaxial progressive damage model is implemented via the user material (UMAT) subroutine to predict the compressive failure behavior of wrinkled composite laminates. This multiscale analysis framework innovatively features a 7 × 7 generalized method of cells coupled with stress-based multiaxial Hashin failure criteria to accurately analyze the impact of wrinkle defects on structural performance and efficiently transfer macro-microscopic damage variables. When any microscopic subcell within the representative unit cell (RUC) satisfies a failure criterion, its stiffness matrix is reduced to a nominal value, and the corresponding failure modes are tracked through state variables. When more than 50% fiber subcells fail in the fiber direction or more than 50% matrix subcells fail in the transverse or thickness direction, it indicates that the RUC has experienced the corresponding failure modes, which are the tensile or compressive failure of fibers, matrix, or delamination in the three axial directions. This multiscale model accurately predicted the load–displacement curves and failure modes of wrinkled composites under compressive load, showing good agreement with experimental results. The analysis results indicate that wrinkle defects can reduce the ultimate load-carrying capacity and promote local buckling deformation at the wrinkled region, leading to changes in damage distribution and failure modes. Full article

Precast prestressed hollow-core slabs (HCSs), primarily designed for uniformly distributed loads, frequently encounter concentrated loads, causing complex stress states. Load distribution occurs through longitudinal joints; however, the hollow cross-section and absence of transverse reinforcement increase susceptibility to shear, including punching. Existing guidelines offer limited guidance, often conflicting with experimental results. While limited previous studies have examined concentrated load effects on various HCS types, research on the Spancrete system—distinguished by unique core geometries—is lacking. This study presents a detailed numerical investigation of modified punching shear behavior in Spancrete HCS floors using a 3D finite element (FE) model developed in ABAQUS. The model, comprising three interconnected HCS units, was validated against experimental data from single-unit and full-scale floor tests exhibiting modified punching shear failure. Results show that modified punching shear in HCSs is driven initially by localized stress distribution in the top flange along one direction and secondarily by compression stresses in the loaded region, unlike the symmetric failure in solid slabs. While variations in loading area affected post-peak response, shifting the load closer to the longitudinal joints led to earlier joint debonding, reducing ultimate capacity. These insights challenge the adequacy of current design guidance and emphasize the necessity of refined HCS provisions. Full article

Climate change remains one of the existential threats to humanity in particular and life on earth in general. It presents significant impacts on food and nutritional security, health, and the general well-being of living organisms globally. Despite global efforts to tackle the climate crisis, the record shows that limited progress has been made in curbing the problem. Consequently, this study intends to address the following research question: How does the climate crisis affect indigenous food systems, farmers’ livelihoods, and local communities in the study area? This study was conducted in the Tolon district of the northern region of Ghana from 2017 to 2022. Grounded in the theoretical prism of political ecology and indigenous knowledge perspective, we selected individuals who were smallholder farmers, students, faculty members, extension officers, and an administrator from the Ministry of Food and Agriculture. The data were gathered through in-depth interviews, focus groups, and workshops and analyzed using coding, thematization, and inferences drawn from the literature and authors’ experiences. This study discovered some of the effects of a changing climate, including the extinction of indigenous food crops, poor yield resulting in poverty, and food and nutritional insecurity. This study concludes that failure to tackle climate change could pose a greater threat to the survival of smallholder households in Ghana. Full article

Constructing an effective importance sampling density is crucial for structural reliability analysis via importance sampling (IS), particularly when dealing with performance functions that have multiple design points or disjoint failure domains. This study introduces an adaptive importance sampling technique leveraging an improved Markov chain Monte Carlo (IMCMC) approach. The method begins by efficiently gathering distributed samples across all failure regions using IMCMC. Subsequently, based on the obtained samples, it constructs the importance sampling density adaptively through a kernel density estimation (KDE) technique that integrates local bandwidth factors. Case studies confirm that the proposed approach successfully constructs an importance sampling density that closely mirrors the theoretical optimum, thereby boosting both the accuracy and efficiency of failure probability estimations. Full article

To reduce the weight of prefabricated cap beams, a new type of hybrid pier with a steel cap beam and single concrete column with an innovative flange–rebar–ultra-high-performance concrete (UHPC) connection structure is proposed in this paper. Focusing on the static performance of hybrid piers, a specimen with a geometric similarity ratio of 1:4 was fabricated for testing. The results showed that the ultimate load-bearing capacity reached 960 kN, and the failure mode was characterized by an obvious overall vertical displacement of 70.2 mm at the cantilever end, accompanied by local buckling in the webs between transversal diaphragms and ribs. Due to the varying-thickness design, longitudinal strains were comparable between the middle section (thin plates) and the root section (thick plates) of the cantilever beam, showing a trend of an initial increase followed by a decrease from the end of the cantilever beam to the road centerline. Meanwhile, the cross-sections of the connection joint and concrete column transformed from overall compression to eccentric compression during the test. At the ultimate state, their steel structures remained elastic, with no obvious damage in the concrete or UHPC, verifying good load-bearing capacity. Furthermore, the finite element analysis showed the new connection joint and construction method of hinged-to-rigid could reduce the column top concrete compressive stress by 18–54%, tensile stress by 11–68%, and steel cap beam Mises stress by 10%. Finally, based on the experimental and numerical studies, the safety reserve coefficient of the new hybrid pier was over 2.7. Full article

Underground high-voltage transmission cables, especially high-pressure fluid-filled (HPFF) pipe-type cable systems, are critical components of urban power networks. These systems consist of insulated conductor cables housed within steel pipes filled with pressurized fluids that provide essential insulation and cooling. Despite their reliability, HPFF cables experience faults caused by insulation degradation, thermal expansion, and environmental stressors, which, due to their subtle and gradual nature, complicate incipient fault detection and subsequent fault localization. This study presents a novel, proactive, and retrofit-friendly predictive condition monitoring method. It leverages distributed accelerometer sensors non-intrusively mounted on the HPFF steel pipe within existing manholes to continuously monitor vibration signals in real time. A physics-enhanced convolutional neural network–long short-term memory (CNN–LSTM) deep learning architecture analyzes these signals to detect incipient faults before they evolve into critical failures. The CNN–LSTM model captures temporal dependencies in acoustic data streams, applying time-series analysis techniques tailored for the predictive condition monitoring of HPFF cables. Experimental validation uses vibration data from a scaled-down HPFF laboratory test setup, comparing normal operation to incipient fault events. The model reliably identifies subtle changes in sequential acoustic patterns indicative of incipient faults. Laboratory experimental results demonstrate a high accuracy of the physics-enhanced CNN–LSTM architecture for incipient fault detection with effective data feature extraction. This approach aims to support enhanced operational resilience and faster response times without intrusive infrastructure modifications, facilitating early intervention to mitigate service disruptions. Full article

The growing demand for lightweight and reliable structures across aerospace, automotive, marine, and civil engineering has driven significant advances in polymer adhesive technology. These materials serve dual roles, functioning as matrices in composites and as structural bonding agents, where they must balance strength, toughness, durability, and sometimes sustainability. Recent review efforts have greatly enriched understanding, yet most approach the topic from specialized angles—whether emphasizing nanoscale toughening, multifunctional formulations, sustainable alternatives, or microscopic failure processes in bonded joints. While such perspectives provide valuable insights, they often remain fragmented, leaving open questions about how nanoscale mechanisms translate into macroscopic reliability, how durability evolves under realistic service conditions, and how mechanical responses interact across different loading modes. To address this, the present review consolidates knowledge on the performance of polymer adhesives under tension, shear, fracture, fatigue, creep, and impact. By integrating experimental findings with computational modeling and emerging data-driven approaches, it situates localized mechanisms within a broader structure–performance framework. This unified perspective not only highlights persistent gaps—such as predictive modeling of complex failure, scalability of nanomodified systems, and long-term durability under coupled environments—but also outlines strategies for developing next-generation adhesives capable of delivering reliable, high-performance bonding solutions for demanding applications. Full article

The surrounding rocks of roadways are typically subjected to cyclic loading–unloading stress states in underground engineering. In addition, cyclic loads are discontinuous under real working conditions, usually while loading rock mass in a cycle–intermission–cycle manner. Based on the XTDIC 3D (XTOP Three-dimensional Digital Image Correlation) full-field strain measurement system and AE (Acoustic Emission) system, the work performed uniaxial cyclic loading–unloading tests with constant-pressure durations of 0, 0.5, 2, and 6 h. The purpose was to investigate the damage degradation mechanism of sandstone under multi-stage equal-amplitude intermittent cyclic loading and unloading. The results are as follows. (1) As the constant-pressure duration increased, the uniaxial compressive strength of sandstone samples decreased, along with a decline in elastic modulus and a deterioration in stiffness and deformation recovery capacity. (2) The evolution of deformation localization zones became more intense in sandstone samples during cyclic loading and unloading with the increased constant-pressure duration. The maximum principal strain field became more active at failure. Sandstone samples exhibited shear failure accompanied by spalling failure and an increased failure degree. (3) As the constant-pressure duration increased, the damage variable of sandstone samples increased, indicating that the constant-pressure stage promoted the damage degradation of sandstone samples. The above results reveal the damage degradation mechanism of sandstone under multi-stage equal-amplitude intermittent cyclic loading and unloading, which is of significant importance for maintaining the safety of underground engineering. Full article

The implementation and application of a safety factor (SF)-based numerical framework in FLAC3D-IMASS (Itasca Model for Advanced Strain Softening) is presented for the evaluation of the short-term stability of unsupported underground excavations in sedimentary rock masses during pillar recovery in bord-and-pillar mining. The stability of underground openings during the initial hours post-excavation must be ensured, as they are not accessed thereafter; therefore, short-term stability assessment is essential. The framework was specifically calibrated to field observations and applied to a case study from an Australian bord-and-pillar mine, focusing on plunge and bellout configurations commonly used during the pillar extraction stage to enhance ore recovery. The modelling approach was integrated with rock mass degradation behavior under static loading conditions and was used to calculate three-dimensional distributions of SF to identify potential failure zones. The results demonstrate that the coal (CO) roof scenario generally maintains structural stability, while the impure coal (Cox) roof scenario is observed to exhibit significant instability, particularly at greater excavation advancement. Among the tested bellout geometries, 8.0 m spans were observed to provide improved performance due to shorter tunnel lengths that enhance confinement and reduce the volume of disturbed rock. Overall, the proposed SF framework effectively captures localized failure mechanisms and is demonstrated as a practical design tool for assessing the short-term stability of unsupported structures during critical stages of underground mining operations. Full article