Long-term Behavior Research Articles

Hygro-mechanical long-term behaviour of spruce, pine and lime wood: parameter identification and model validation

Lime wood, spruce and pine are investigated with regard to its hygro-mechanical long-term behaviour. Experiments are conducted for an identification of model parameters and for model validation. Swelling and shrinkage coefficients, dry density, sorption characteristics and parameters for visco-elasticity, visco-plasticity and mechano-sorption are determined for the main material directions. Supplemented by literature values, a complete set of parameters for long-term hygro-mechanical modelling of wood species is found. Constrained swelling and shrinkage are analysed and the origin of the stress development is investigated. It is demonstrated, that creep phenomena lead to significant stress reduction by relaxation, in case of moisture changes especially due to mechano-sorption. The influence of different model parts is investigated. A numerical parameter study shows the influence of several material parameters on the stress evolution. Experimental material investigations such as those presented here are essential for the application of numerical simulation methods for the prediction of material behaviour and for the assessment of deformations, stresses and damage potential of climatically loaded timber structures.

Sorption and desorption behavior and mechanism of oxytetracycline on soil aggregates organic matter separated from soils and sediments in the Yellow River Delta

Soil aggregates organic matter (SAOM) is composed of free particulate organic matter (fPOM), intra-aggregate particulate organic matter (iPOM), and mineral-associated organic matter (mSOM), which are major antibiotic sorbents that play a significant role in the soil organic matter (SOM) turnover process. To date, the oxytetracycline (OTC) sorption and desorption behavior and mechanisms on SAOM have not been contrastively analyzed. SAOM organic components have been used to study scientific problems and to determine their influence on the fate and migration of OTC among the SOM turnover process. Results demonstrated that SAOM had great OTC sorption capacity ranging from approximately 12100–513,000 mg kg−1 and the desorption proportion was no more than 33.60%. The slow organic carbon pool (mSOM) had greater OTC accumulation capacity than the intermediate active pool (iPOM) and the active pool (fPOM), while OTC was more likely to reside in the active pool in wetlands (fPOM-w) and oil waste land (fPOM-o) than the organic carbon pool (mSOM-f) in farmland with human activity interference. The hysteresis was affected by SAOM's physical surface characteristics when the OTC initial equilibrium sorption concentration was higher than 200 mg L−1. When it was lower than that, it was affected by the organic carbon composition. Hydrogen bonds, electrostatic interactions, and π-π interactions dominated the SAOM-OTC interactions. The results of this study will be useful for evaluating the long-term behavior and migration of antibiotics in SOM turnover processes and could refine risk assessments of antibiotics contamination in soil environmental systems.

Performance evaluation of microbial fuel cells for bioelectricity generation: influence of potential scan-rate and real-time external load

AbstractThe electrochemical performance of microbial fuel cells is conventionally assessed through linear sweep voltammetry at predefined potential scan rates. Nevertheless, this approach frequently falls short in representing the long-term behavior of microbial fuel cells under actual external loads, highlighting the need for a standardized evaluation method incorporating both linear sweep voltammetry and external loads. To address this gap, this study evaluates the performance of single-chamber microbial fuel cells under different loads and scan rates. The MFCs were tested with external loads of 1200, 470, and 270 Ω, derived from maximum power points of polarization sweeps at scan rates of 0.1, 0.5, and 1 mV/s at two operational phases. Power estimates at these scan rates were 61.96, 87.88, and 166.68 mW/m2 at current densities of 116.5, 229.6, and 403 mA/m2, respectively. In the initial two hours, average power densities with 1200, 470, and 270 Ω were 73 ± 16.7, 36.3 ± 42, and 88.5 ± 120.1 mW/m2, respectively. Over the long term, the fuel cells under constant loading with resistance estimated at 0.1 mV/s showed average power 73.7% and 89.1% higher than those with resistances estimated at 0.5 mV/s and 1 mV/s, respectively, indicating that higher scan rates lead to overestimation of power. Although initially underestimated, the 0.1 mV/s scan rate more accurately reflected the true long-term performance of the fuel cells. This study emphasizes the importance of using appropriate scan rates for linear sweep voltammetry to obtain realistic long-term performance estimates of microbial fuel cells under real-time loads.

Century-scale dataset of bathymetry and shoreline position for Tagus ebb-tidal delta, Portugal

Understanding long-term coastal changes requires comprehensive records of morphological data spanning extended periods, ideally over multiple decades. Nevertheless, significant challenges arise from the restricted availability and accessibility of reliable data, especially in the case of complex coastal systems dominated by wave-current dynamics, such as ebb-tidal deltas (ETDs). This study introduces a new dataset for Tagus ETD in central Portugal, from 1845 to 1985 based on historic nautical charts available for the area. The data includes: (1) high-resolution bathymetric surfaces of ETD configuration for years 1845, 1879, 1893, 1929, 1939, 1960 and 1985; (2) shoreline position of three different indicators (Low-Water Line, High-Water Line and foredune dune seaward limit) at the adjacent coast for the same years; (3) rates-of-change for shoreline position of the High-Water Line indicator. Data also includes an uncertainty assessment for hydrographical and shoreline position information estimated from historic nautical charts. These data provide a valuable resource for describing, understanding, and modelling the long-term behaviour of ETDs not covered by other currently available datasets.

Temporal trends in asteroid behaviour: a machine learning and N-body integration approach

ABSTRACT Asteroids pose significant threats to Earth, necessitating early detection for potential deflection. Leveraging machine learning (ML), we classify asteroids into near-Earth Asteroids (particularly Atens, Amors, Apollos, and Apoheles) and non-near-Earth asteroids, further categorizing them based on hazard potential. Training the seven models on a comprehensive data set of 4687 asteroids, we achieve high accuracy in prediction. The predictive capability of these models is critical for informed decision-making in planetary defense strategies. We apply different regularization techniques to prevent overfitting and validate the models using a large unseen data set. A rigorous long-term N-body integration spanning 1 Myr is executed utilizing the Mercury N-body integrator to illuminate the evolution of asteroid properties over extended temporal scales. Following this integration process, the best-performing ML model is employed to classify asteroids based on their orbital characteristics and hazardous status respectively. Our findings highlight the effectiveness of ML in asteroid classification and prediction, paving the way for large-scale applications. By dividing a 1 Myr integration into intervals, we uncover temporal trends in asteroid behaviour, revealing insights into hazard evolution and ejection patterns. Notably, initially, hazardous asteroids tend to transition to non-hazardous states over time, elucidating key dynamics in planetary defense. We illustrate these findings through plotted graphs, providing valuable insights into asteroid dynamics. These insights are instrumental in advancing our understanding of long-term asteroid behaviour, with significant implications for future research and planetary protection efforts.

Progressively advantageous long-term corrosion profile of Mo over Mg, Zn, and Fe from the perspective of biodegradable metals

Long-term corrosion profile of molybdenum was studied in three different simulated body fluids up to 28 days, compared with magnesium, zinc, and iron from the perspective of biodegradable metals (bio-metals). Their corrosion rate, mode, products and surface characteristics were comprehensively fathomed. Strikingly, Mo showed progressively advantageous long-term corrosion behavior with the smallest corrosion rate, and most importantly, more uniform mode, as compared with the other three bio-metals. It also performed bilaterally under the simulated inflammatory and bovine serum protein added conditions, with different corrosion progressions. These findings provide an optimistic outlook in opting molybdenum as a new type of bio-metal.

Long-term thermal aging effects in ferritic-martensitic steel HT9

The ferritic-martensitic steel HT9 is a candidate material for fuel cladding and core components in advanced nuclear reactors, such as sodium-cooled fast reactors, thanks to their high temperature mechanical properties and low susceptibility to irradiation induced swelling phenomena. However, thermal stability and elevated temperature microstructural evolution in these alloys may impact their long-term behavior and reliability. In this work, the effects of thermal aging on the microstructural and mechanical properties of HT9 have been investigated through complementary electron microscopy, synchrotron X-ray diffraction, microhardness, and thermodynamic modeling. Plates of HT9 were aged up to 50 kh at relevant sodium-cooled fast reactor operational temperatures (360 °C - 700 °C). Trends in microstructure as a function of aging time and temperature were apparent from qualitative and quantitative analysis. These observations were further supported by thermodynamic modeling of the bulk and precipitate phases. Specific phases observed include BCC Fe, FCC M23C6, HCP and FCC MX phase and Laves M2X phase. Through the application of our multi-scale and multi-modal approach, clear information on the aging mechanism of HT9 was obtained, allowing for a more informed prediction, and understanding of the long-term behavior, performance and thermal stability of ferritic-martensitic alloys exposed to elevated temperatures.

TESS observations of non-Be fast rotators

Context. The variability of fast-rotating Oe/Be stars has been reported in detail in recent years. However, much less is known about the behaviour of fast-rotating OB stars without known decretion disks, and hence it is difficult to identify the commonalities and differences in the photometric variability of these two populations, especially with regards to their pulsational properties and their link with the presence of circumstellar material. Aims. Via an in-depth literature search, we identified a set of fast-rotating (vsin(i) > 200 km s−1) early B-type stars not known to have disks. TESS and Kepler light curves were built for 58 stars that appear isolated (no bright neighbour within 1′ and no known companion) to avoid contamination of the light curves. Frequency spectra were calculated and then analysed to determine the noise level and the presence of significant signals above the noise. Methods. Red noise is detected in all targets, without obvious correlations between noise and stellar parameters. Long-term changes are much less frequent than in Be stars, with only 12% of our targets having the variability below 0.5 d−1 dominating their frequency spectrum. In contrast, strong frequency groups are detected in about a third of targets, as in Be stars. These groups generally occur in pairs with harmonic frequencies, as is usually seen in Be stars, but with the first group more often displaying larger amplitudes. Finally, the most frequent variability is due to isolated frequencies in the 0.5–6. d−1 range (which is found in two-thirds of cases and dominates the spectra in 42% of the sample). Higher-frequency signals (up to 40 d−1) are sometimes also detected but rarely (only 12% of stars) appear as the strongest ones of the frequency spectra. Overall, fast-rotating B-type stars, with or without disks, display similar photometric properties, except as regards their longer-term behaviour.

Improving the Automated Coronal Jet Identification with U-NET

Coronal jets are one of the most common eruptive activities in the solar atmosphere. They are related to rich physics processes, including, but not limited to, magnetic reconnection, flaring, instabilities, and plasma heating. Automated identification of off-limb coronal jets has been difficult due to their abundant nature, complex appearance, and relatively small size compared to other features in the corona. In this paper, we present an automated jet identification algorithm (AJIA) that utilizes true and fake jets previously detected by a laborious semiautomated jet detection algorithm (SAJIA) as the input of an image segmentation neural network U-NET. It is found that AJIA can achieve a much higher (0.81) detecting precision than SAJIA (0.34) while giving the possibility of whether each pixel in an input image belongs to a jet. We demonstrate that with the aid of artificial neural networks, AJIA can enable fast, accurate, and real-time off-limb coronal jet identification from Solar Dynamics Observatory/Atmospheric Imaging Assembly 304 Å observations, which are essential in studying the collective and long-term behavior of coronal jets and their relation to the solar activity cycles.

Research Paper on Analytical Investigation of the Effect of 3d Printing Process Parameters on Anisotropic Mechanical Behaviour of Additively Constructed Concrete

This research identifies key challenges in additively constructed concrete, including the need for understanding the scalability of mechanical behaviour from small to large structures, addressing variability in material properties, and predicting failure mechanisms. It highlights the need for improved finite element modelling for accurate 3DCP simulation, and further investigation into concrete foundation interactions and initial imperfections. The study acknowledges difficulties in simulating complex shapes and calls for refinement of the numerical model for better predictive accuracy. It also emphasizes the need to understand long-term behaviour, durability, and the impact of the 3DCP process on microstructural morphology and mechanical properties. The influence of pores and time gaps between layers on the overall capacity of the specimen, and the development of a model considering different properties of 3D concrete material are also identified as areas for future research.

Long-term deterioration behavior of round-end hollow piers during cyclic solar radiation

Reinforced concrete (RC) hollow piers are inevitably impacted by solar radiation during their service life. However, normal investigation approaches are inadequate for characterizing the long-term degeneration of RC structures under cyclic solar radiation. In this article, a novel elastoplastic-thermodynamic numerical approach has been suggested for evaluating the long-term deterioration behavior of hollow piers during cyclic solar radiation and ambient temperature fluctuations. The findings suggest thermal effect caused by solar radiation and ambient temperature fluctuations might cause the pier surface concrete to crack. The maximum first principal strain of pier surface concrete in July is approximately 1.21 times greater than the concrete peak tensile strain. Tensile damage of pier concrete rises with cyclic times of solar radiation. Tensile damage of surface concrete rose from 0.495 to 0.566 and 0.610, as exposure time increased from 1 to 10 and 100 years. Reducing the surface short wave absorption rate, increasing concrete specific heat, and decreasing pier wall thickness is beneficial to minimizing long-term tensile damage of pier concrete.

A numerical algorithm for damage progression of reinforced concrete bridge piers during air temperature and solar radiation cycles

Reinforced concrete (RC) solid piers are unavoidably affected by air temperature changes and solar radiation during service life. Nevertheless, the deterioration of pier concrete with increased exposure age remains unclear. A novel thermal-mechanical numerical algorithm (finite element model) for characterizing the deterioration characteristics of RC structures under cyclic environmental loads has been suggested. The deterioration of RC pier concrete after 100 years of air temperature and solar radiation cycles is simulated. The numerical results demonstrate that tensile damage of pier concrete during air temperature and solar radiation cycles increases continuously with exposure age. After one year of exposure, the tensile damage value of pier surface concrete increased to 0.201 and further increased to 0.286 and 0.357 as the exposure age grew to 10 and 100 years. Pier concrete tensile damage can be mitigated by using surface short-wave absorption-reducing methods, controlling the thermal properties of concrete, and raising the concrete peak tensile strain. The proposed finite element framework and numerical solutions enable a viable simulation-based method for the analysis of bridge structural long-term deterioration behavior and design of the bridge engineering.

Linear stability analysis of the viscoelastic Navier–Stokes–Voigt fluid model through Brinkman porous media: Modal and non-modal approaches

The linear stability analysis of a viscoelastic Navier-Stokes-Voigt fluid flow, or the Kelvin-Voigt fluid of zero order in a Brinkman porous medium, is investigated using both modal and non-modal analysis. The numerical solution is obtained using the Chebyshev collocation method. The combined effects of the medium's porosity, represented by the porous parameter, the fluid viscosity, represented by the ratio of effective viscosity to fluid viscosity, and the fluid elasticity, represented by the Kelvin-Voigt parameter are investigated using both modal and non-modal analysis. The modal analysis describes the long-term behavior of the system, obtained through plotting the eigenspectrum, eigenfunctions, growth rate curves, neutral stability curves, and streamline plots, along with accurate values of critical triplets. In non-modal analysis, the pseudospectrum of the Orr-Sommerfeld operator, transient energy growth curves, and regions of stability, instability, and potential instability are depicted. The results obtained from modal analysis indicate that the porous parameter, Kelvin-Voigt parameter, and the ratio of effective viscosity to fluid viscosity act as stabilizing agents. However, using non-modal analysis, it is observed that while the porous parameter and the ratio of effective viscosity to fluid viscosity act as stabilizing agents, the Kelvin-Voigt parameter acts as a destabilizing agent over shorter periods.

Long-term oxidation resistance of CrAl(Si)N coatings deposited on TiAl-based alloy at 950 °C

CrAl(Si)N coatings were deposited on Ti-48Al-2Cr-2Nb alloy by arc ion plating. Long-term cyclic oxidation behaviors of the CrAl(Si)N-coated alloy were investigated at 950 °C. The oxidation resistance of the Cr0.4Al0.5Si0.1N coating was significantly better than that of the Cr0.5Al0.5N coating. The addition of Si to the CrAlN coating promoted the formation of an almost continuous inner Al2O3 layer in the oxide scale. The continuous and dense Cr2O3/Al2O3 oxide layer acted as a diffusion barrier and retarded the inward diffusion of oxygen and outward diffusion of the coating elements. However, interdiffusion between the CrAl(Si)N coatings and the alloy was serious and a thick interdiffusion zone formed.

Atmospheric NH3 in urban Beijing: long-term variations and implications for secondary inorganic aerosol control

Abstract. Ammonia (NH3) has major effects on the environment and climate. In situ measurements of NH3 concentrations taken between June 2009 and July 2020 at an urban site in Beijing were analyzed to study its long-term behavior, responses to meteorological conditions, and influences on the formation of secondary inorganic aerosols (SIAs). The 11-year average NH3 mixing ratio was 26.9±19.3 ppb (median 23.5 ppb). The annual average NH3 mixing ratio increased from 2009 to 2017 by 50 % and then decreased by 49 % from 2017 to 2020. Notably, the long-term trend for NH3 at the ground level did not align with the trends derived from satellite observations and emission estimates. The NH3 concentration exhibited a stronger correlation with the daily variation in water vapor (H2O) concentration than with air temperature. Thermodynamic modeling revealed the nonlinear response of SIAs to NH3, with increased sensitivity when its concentration was reduced to 40 % of the initial level. Although reducing NH3 concentrations can improve air quality during winter, controlling acid gas concentrations has a greater effect than controlling NH3 concentrations on reducing SIA concentrations, until NH3 and acidic gas concentrations are reduced below 80 % of their current levels. Nevertheless, the increased mass proportion of ammonium salts in SIAs during the observation period indicates that future control measures for NH3 concentrations may need to be prioritized in Beijing.

The causality between smoking and intervertebral disc degeneration mediated by IL-1β secreted by macrophage: A Mendelian randomization study

There is still a lack of high-level evidence regarding the causal relationship between smoking and intervertebral disc degenerative diseases. This study utilized data from genome wide analysis studies and conducted two-sample Mendelian randomization analyses across multiple heterogeneous datasets. We evaluated the causal relationships between smoking behavior, serum inflammatory factors, serum chemokines, and intervertebral disc degeneration. Sensitivity analysis was performed to examine data heterogeneity and the pleiotropy of causal effects. The results indicated that smokers were liable to develop intervertebral disc degeneration (OR 1.770; 95 % CI, 1.519–2.064; p = 2.992 × 10–13), and long-term smoking behavior increased the risk of intervertebral disc degeneration (OR 1.715; 95 % CI 1.475–1.994; P = 2.220 × 10–12). Additionally, a causal relationship was confirmed between serum IL-1β level and intervertebral disc degeneration (OR 1.087; 95 % CI, 1.023–1.154; p = 0.007). The “smoking index” representing lifelong smoking habit was also found to be causally related to serum MCP-3 level(β = 0.292; SE = 0.093; p = 0.002). All of the causality mentioned above remained stable in sensitivity tests. Based on the analysis results and fundamental medicine theories around macrophage-induced inflammation in degenerative intervertebral discs, we have constructed a new mechanism that long-term smoking could induce an increase in serum MCP-3 level, promoting the gathering and activation of monocyte macrophages. Furthermore, the recruited macrophages led to an increase in local IL-1β within the intervertebral disc, ultimately exacerbating the process of intervertebral disc degeneration. What we have found is expected to accelerate the development of prevention and treatment of intervertebral disc degeneration.

MHealth learning strategies to support behaviour change in individuals using wheelchairs and/or scooters: a systematic review.

The purpose of this systematic review of the literature is to build understanding of the key elements and recommendations for the design of mHealth technology for individuals using wheelchairs and/or scooters and identify key features associated with the use of mHealth to support healthy behaviour changes for this population. Eight major electronic databases were systematically searched to identify mobile health (mHealth) interventions, which targeted adult WC/S users. Independent reviewers used Endnote and Covidence to manage articles meeting review criteria and to exclude duplicates. A quality assessment was conducted on each included article. Nine articles describing studies with diverse study designs met criteria to be included in this review. Several interactive application intervention features, such as participant collaboration and goal setting, and key technical features to support mHealth app development and utilisation were identified. Results found intuitive and simple designs of mHealth apps, with the ability to customise to support learning styles and preferences, support usability and acceptability by participants. More research is needed to evaluate best practices to support initial training of end-users, mHealth apps' ability to support long-term behaviour change and maintenance, and the understanding of active ingredients in complex interventions that include mHealth apps. Both interactive mHealth application intervention and technical features support healthy behaviour change among individuals using wheelchairs and scooters.

Together we win! Narratives of couples pursuing a healthy diet and physical activity: A qualitative study.

Metabolic syndrome (MetS) is a major risk factor for non-communicable diseases, including type 2 diabetes mellitus, cardiovascular disease, and cancer. The risk of MetS can be transmitted via epigenetic processes from both the mother and the father. Therefore, it is essential that both members of a couple are targeted in pre-conception nutrition and physical activity-based lifestyle programs. However, lifestyle interventions targeting both members of a couple are scarce in the literature. This study, therefore, aimed to explore the barriers and facilitators of a couples-based lifestyle intervention. Nulliparous couples who had an interest in having children in the future were recruited to the study and each member interviewed separately to gain insight into to gain insight into designing future couples-based lifestyle interventions. Interviews were conducted between June and October 2021. Reflexive thematic analysis (RTA) was applied to conduct and analyse semi-structured, in-depth interviews with nulliparous couples who had an interest in having children in the future. Four major themes were identified in nine couples aged 25-34 years (here referred to as "millennials"): Millennials are committed to preparation for their future offspring; millennials know features of a good program likely to have high adherence and long-term behavior change; millennials acknowledge the importance of couples-based programs; and millennials appreciate that future global emergencies may require lifestyle modifications. This study found that millennial couples showed a strong intention to create optimal emotional, financial, and health conditions for their children. They supported couples-based approach (CBA) lifestyle interventions to mitigate potential epigenetic risks. Couples believed that participating together in these programs would enhance adherence to healthy habits, promoting long-term well-being. The findings advocate for exploring and testing CBA interventions that target both partners, as joint participation not only aids in healthy conception and reduces metabolic syndrome risks but also establishes a foundation for family health. These insights highlight the potential of CBA interventions to positively impact future generations.

On a nonlinear difference equation of the fourth order solvable in closed form and its solutions

We show that a nonlinear difference equation recently considered in this journal is a special case of a solvable class of nonlinear difference equations and that the difference equation is closely related to a difference equation previously considered in the literature. We give some detailed theoretical explanations for the closed-form formulas for the solutions to the four special cases of the difference equation considered therein without giving and theoretical explanations related to them, and also show that several statements on the long-term behaviour of positive solutions to the difference equation are not true.

Leveraging Multi-Temporal InSAR Technique for Long-Term Structural Behaviour Monitoring of High-Speed Railway Bridges

The effective monitoring of railway facilities is crucial for safety and operational efficiency. This study proposes an enhanced remote monitoring technique for railway facilities, specifically bridges, using satellite radar InSAR (Interferometric Synthetic Aperture Radar) technology. Previous studies faced limitations such as insufficient data points and challenges with topographical and structural variations. Our approach addresses these issues by analysing displacements from 30 images captured by the X-band SAR satellite, TerraSAR-X, over two years. We tested each InSAR parameter to develop an optimal set of parameters, applying the technique to a post-tensioned PSC (pre-stressed concrete) box bridge. Our findings revealed a recurring arch-shaped elevation along the bridge, attributed to temporal changes and long-term deformation. Further analysis showed a strong correlation between this deformation pattern and average surrounding temperature. This indicates that our technique can effectively identify micro-displacements due to temperature changes and structural deformation. Thus, the technique provides a theoretical foundation for improved SAR monitoring of large-scale social overhead capital (SOC) facilities, ensuring efficient maintenance and management.