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Modular QZS metamaterials with enhanced load adaptability for low-frequency vibration isolation
No full textAbstract
This study introduces a modular quasi-zero-stiffness (QZS) metamaterial for low-frequency vibration isolation with adaptable load-carrying capacity. The proposed structure integrates a double-curved beam as a negative stiffness (NS) element and two pairs of V-shaped springs as positive stiffness (PS) elements, forming an extendable modular metamaterial. These metamaterials provide scalable and tunable load-adaptive performance through multiple modular configurations. Finite element analysis (FEA) is utilized to optimize the design parameters, ensuring effective and consistent QZS behavior across the modules. A dynamic model, validated using harmonic balance methods, demonstrates the isolation effectiveness under varying loads and excitation amplitudes. By arranging multiple unit modules in series, parallel, or combined configurations, the QZS characteristics scale in a linear and predictable manner, enabling versatile load adaptability and tunability. Quasi-static tests confirm the predicted QZS behavior, while dynamic tests validate the vibration isolation performance. A single unit module attenuates vibrations at 8.6 Hz with a payload of 1420 g, while the modular configuration achieves vibration suppression above 4.2 Hz for payloads ranging from 4320 g to 5680 g, without requiring alterations to the design parameters. These findings underscore the potential of the proposed modular QZS metamaterial for scalable, load-adaptive, and low-frequency vibration isolation in engineering applications.&#xD;</jats:p
Large and Increasing Biospheric Productivity of Northern Ecosystems
Get PDFPlants take up carbon dioxide (CO2) through photosynthesis. How this will change with rising CO2 concentrations in the atmosphere will strongly determine future climate change. An increase in the seasonal variations of atmospheric CO2 in recent decades indicates a positive trend in photosynthetic carbon uptake. We combined data-driven seasonal cycles of plant productivity with carbon sinks across the range predicted by current biospheric process models to explain the seasonal variations of CO2 at high and low northern latitudes over the past 40 years. We find that increases in seasonal variations can only be explained by a larger gross primary productivity (GPP) of northern ecosystems than most current estimates and by an increase of GPP about proportional to the increase in atmospheric CO2, also larger than most current estimates. Our results provide an improved constraint to estimate the future behavior of the terrestrial carbon sink
Avoiding Diagnostic Overshadowing: A Case Report of ACL Rupture and Concurrent Thromboembolism
Get PDFMagnetic Resonance Imaging (MRI) plays an integral role in the evaluation of musculoskeletal injuries, especially in the context of acute knee injuries. However, relying solely on imaging studies and not incorporating clinical evaluation may result in missed diagnoses of other important and potentially fatal conditions. We present a case of a 45-year-old male patient with an anterior cruciate ligament (ACL) tear and meniscal tears who, upon careful clinical examination, was incidentally discovered to have deep vein thrombosis (DVT) along with bilateral pulmonary embolism (PE). This case highlights the importance of a comprehensive physical examination and evaluation in conjunction with advanced imaging techniques
How Lattice Strain Affects Nonradiative Recombination and Mobility in FAPbI3.
No full textThe lattice strain resulting from the fabrication process in hybrid organic-inorganic halide perovskites (HOIPs) and its dynamic changes under illumination are the key factors that affect the efficiency and intrinsic stability of HOIP-based solar cells. However, there is still a lack of comprehensive and in-depth understanding regarding how lattice strain influences the dynamic behavior and transport properties of charge carriers in organic-inorganic halide perovskites (HOIPs), as well as how light illumination triggers lattice strain. Here, our simulation results indicate that a 1% compressive stress delays hot electron cooling and increases the electron mobility by around 50%, while a 1% tensile stress accelerates cooling and reduces the electron mobility by about 37%. Additionally, both compressive and tensile strains accelerate electron-hole recombination. These important phenomena are mainly attributed to the modulation effect of strain on the thermal vibration of the lattice and the energy-level redistribution. Additionally, the research also reveals that the photoinduced dynamic lattice strain is due to the changes in Pb-I bonds jointly driven by the electron-phonon interaction and anharmonic lattice characteristics of HOIPs. This work provides new and systematic insights into the influence of strain on carrier dynamics and transport properties in HOIPs, which holds significant implications for enhancing the efficiency and stability of HOIP-based solar cells
Challenges and Enablers of Antiretroviral Therapy Adherence Among Ethiopian Adolescents: A Qualitative Study
Get PDFBackground: Despite global decline in acquired immunodeficiency syndrome (AIDS)-related mortality, adolescent (10–19 years) deaths are rising. Adolescents living with Human Immunodeficiency Virus (ALHIV) face unique antiretroviral therapy (ART) adherence challenges, especially in low-income settings. This study explores factors influencing ART adherence among Ethiopian adolescents. Methods: A qualitative study was conducted with 12 ALHIV from August to September 2021in Ethiopia’s Amhara Region. Semi-structured interviews were conducted, transcribed, and analyzed using deductive coding and an interpretive phenomenological approach. Results: The analysis explored three prominent themes: (1) culture and religion, (2) connection and belonging, and (3) stigma and mental health. These themes collectively provide a comprehensive understanding of the barriers and facilitators influencing adolescent adherence to ART. Cultural and religious beliefs, especially those held by parents, such as misconceptions about long-term medication use, side effects of ART, and illness as divine punishment, acted as barriers to adherence. On the other hand, connection and belonging through family, community support, and shared experiences with peers facilitated adherence. However, stigma—whether internalized, experienced, or anticipated—caused isolation and mental health challenges, creating significant barriers to treatment adherence. Conclusion: This study sheds light on the multifaceted challenges faced by adolescents in adhering to HIV treatment, including cultural misconceptions, social and familial dynamics, and mental health barriers. Addressing these issues requires culturally sensitive health education and fostering environments that promote connection and support. Community-based interventions and peer networks can play a pivotal role in strengthening adherence, while stigma-reduction efforts are essential to addressing the mental health challenges adolescent’s encounter. The findings highlight the need for a holistic approach integrating health education, stigma reduction, provider training, and mental health support to enhance adherence and outcomes for ALHIV
The Modifying Effects of Meteorological Factors on the Association between Short-term PM2.5 Exposure and Daily Lung Cancer Deaths in Jining, China
No full textPorewater pressure-based consolidation analysis using field data in a vacuum-preloaded soft soil foundation at Fisherman Island, Australia
No full textInfrastructure development in Australia’s coastal regions often encounters geotechnical challenges due to the widespread presence of very soft clay deposits. These soils significantly compromise the serviceability and stability of foundations supporting transport corridors, buildings, and port facilities. Vacuum preloading has been widely adopted for large-scale soft soil sites. However, the ability to accurately monitor consolidation and minimize long-term settlements remain practically challenging in field applications. In this study, two distinct observational approaches based on surface settlement and porewater pressure measurements were employed and compared at a vacuum consolidation site at the Port of Brisbane. The consolidation assessments derived from the strain-based and porewater pressure-based methods were found to exhibit a strong relationship, reinforcing the practical value of using field porewater pressure data. The concept of residual excess porewater pressure was established through the observed porewater pressure data (un – un+1 plot) and incorporated into the porewater pressure-based degree of consolidation assessment
Construction Delays Due to Weather in Cold Regions: A Two-Stage Structural Equation Modeling and Artificial Neural Network Approach
Get PDFSignificant weather-induced delays often plague construction projects in India’s extremely cold regions, yet comprehensive studies addressing this issue remain scarce. This study aims to fill this gap by identifying key delay factors and proposing mitigation strategies for the construction industry. Through an extensive literature review, 42 delay factors were identified and categorized into four groups. A survey of 83 experts from cold regions was conducted to evaluate these factors’ significance to contractors and subcontractors. Employing exploratory factor analysis (EFA), structural equation modeling (SEM), and artificial neural networks (ANN), the study analyzed the relationships between these factors and ranked their impact. The findings reveal that snowfall, rainfall, and low temperatures are the most significant contributors to delays, with snowfall being the most influential (significance: 1.000), followed by rainfall (0.890) and low temperatures (0.790). This research establishes a risk hierarchy and develops a predictive model to facilitate the proactive scheduling of challenging tasks during favorable seasons. This study advances the understanding of weather-induced delays in India’s cold regions and offers valuable insights for project management in such climates. However, it underscores the importance of clearly articulating its novel contributions to differentiate it within the existing literature on weather-related construction delays
Ultrawideband and Near-Perfect Center-Frequency Absorption Enabled by Lüneburg-Inspired 3-D-Printed Superstrate and Hyper-Fine Meshing
No full textThis article presents a pair of multifunctional microwave absorbers that simultaneously achieve ultrawideband absorption and near-perfect attenuation at their center frequencies, thereby bridging the application needs of both broad bandwidth and high selectivity. Despite employing only a single-layer frequency-selective surface (FSS) composed of fundamental shapes, the finalized designs elevate the absorption potential of the unit-cell topology through two key strategies: a 3-D-printed gradient-index superstrate and laser-etched hyper-fine meshes. The former leverages analytically prescribed air cavities to establish a continuous effective permittivity gradient, which enhances impedance matching with free space. The latter facilitates precise adjustment of load resistances for individual resonators while preserving high independence from the capacitive and inductive elements of the equivalent circuit. These broadly applicable strategies are supported by a suite of closed-form expressions and semi-analytical formulas, also ensuring compatibility with readily available materials and practical fabrication techniques. The experimentally validated absorbers attain approximately 99.9% absorption at the center frequency, while exhibiting fractional bandwidths (FBWs) of 138.2% and 137.1% at the 90% absorption threshold, sustained with compact normalized thickness of 0.11 λL. Notably, their operational bandwidths remain largely intact at the more stringent 95% absorption level, measuring 132.2% and 129.8%, respectively
Resilience assessment in post-wildfire recovery of road transport networks by dynamic thresholds and characteristic curves
Get PDFUnderstanding and enhancing the resilience of transport networks against climate-induced extreme events, such as wildfires, is critical to minimizing disruptions and their societal impacts. In this context, resilience is essential for effectively coping with these hazards, as road disruptions can hinder evacuation efforts, reduce accessibility, and lead to significant economic losses. Despite scientific progress, existing resilience assessment frameworks have limitations, including scenario-specific results and limited consideration of the underlying resilience concepts. To address these limitations, this paper introduces a resilience framework based on dynamic thresholds and characteristic curves to evaluate system recovery capacity. The framework incorporates a temporal dimension, allowing for the analysis of recovery time and recovery rate, which depend on the resources available for recovery activities. The characteristic curves illustrate system resilience by capturing key information on the preparedness, response, and recovery capacities inherent in each network. Consequently, the framework offers a more comprehensive view of system behavior during the recovery stage, as demonstrated through its application to a Portuguese case study. The insights gained can assist stakeholders in determining the feasibility of strengthening system resilience through enhanced response and recovery efforts, as well as in identifying when it is critical to reinforce resilience at earlier stages through adaptation measures
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