Global Loading Research Articles

Accuracy assessment of global vertical displacement loading tide models for the equatorial and Indian Ocean

Accuracy assessment of global vertical displacement loading tide models for the equatorial and Indian Ocean

Rising CO2 and land use change amplify the increase in terrestrial and riverine export of dissolved organic carbon over the past four decades

The lateral transport of dissolved organic carbon (DOC) from land to rivers and oceans is a significant but overlooked component of the global carbon cycle. However, there are still large uncertainties in the magnitude and trend of global DOC export fluxes, as well as their response to environmental change. In this study, several simulations were conducted using a developed land surface model that considered riverine DOC transport and anthropogenic disturbance to investigate the terrestrial DOC loading and riverine DOC export, and to quantify the relative contributions of natural and anthropogenic factors over the past four decades (1981–2016). These factors include climate change, nitrogen deposition, land use change, atmospheric CO2 concentration, anthropogenic water regulation, and fertilizer and manure application. Results showed that the average global annual terrestrial DOC loading was about 432.30 ± 53.59 Tg C yr−1, and rivers exported about 209.73 ± 36.58 Tg C yr−1 to oceans over the past four decades. Simultaneously, a significant increase in terrestrial DOC loading and riverine DOC export fluxes (3.36 Tg C yr−2 and 2.99 Tg Cyr−2, p < 0.01) was found, which increased by 26.88 % and 47.02 %, respectively. According to our factorial analysis, the interannual variability in DOC fluxes in most regions was mainly attributed to climate change and contributed more than 60 % of the long-term increase. In addition, rising atmospheric CO2 and land use change amplified the increase in terrestrial DOC loading, with the area dominated by the two factors expanding from 7.94 % in the 1980s to 23.84 % in the 2010s, and riverine DOC export showed a similar pattern, which may be related to the increased soil DOC sources. Anthropogenic water regulation and nitrogen addition have led to a slight increase in DOC fluxes, which should not be ignored, otherwise carbon fluxes may be underestimated.

The structure, development, and etiology of observed temperament during middle childhood.

Investigating the structure and etiology of temperament is key to understanding how children interact with the world (Kagan, 1994). Although these topics have yielded an abundance of research, fewer studies have employed observational data during middle childhood, when unique environmental challenges could influence temperament development. To address this gap, Israeli twin children were observed at Age 6.5 (N = 1,083, 564 families; 50.6% females) and again at Age 8-9 (N = 768, 388 families; 52.0% females; 611 children from 322 families had data from both ages). Temperament was assessed globally by trained coders and, at Age 8-9, also by the experimenter who interacted with the child. We examined whether Rothbart et al.'s (2000) three-factor model, according to which temperament includes the domains negative affect, positive affect/surgency, and effortful control, emerges from the data. In addition, we considered a bifactor model, where a fourth global factor accounts for all behaviors' commonality. Across the two ages and rating methods, confirmatory factor analyses supported the bifactor model. The global factor's loadings suggested that it reflects children's expressiveness. Adding this factor changed the associations between the other factors and enabled differentiation between surgency and positive affect. This suggests that in observational settings that capture temperament impressions holistically, children's expressiveness affects other traits' behavioral displays. Twin models revealed genetic influences for most traits. Importantly, twin models revealed shared-environmental influences for negative affect and expressiveness, which modestly contributed to temperament consistency across ages. These findings shed light on temperament traits' interrelatedness and stress the importance of the shared environment to temperament development during middle childhood. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Applying Cross-Validated Psychometric Models to the Bavarian Reading Test (BYLET)

Abstract: In this study, we compared three different models of reading comprehension on a large dataset of more than 6,500 students. We compared two models representing four comprehension processes as well as the influence of text difficulty to a one-factor model by applying multi-dimensional item response models to the newly developed Bavarian reading test (BYLET). Cross-validation indicated the best generalizability for the one-factor model, but factor loadings and global model fit showed some evidence for the influence of text difficulty measured by word and sentence length and the process structure. All psychometric models tested had a good fit, as indicated by global fit indices and loading patterns. The general factor scores point to reliability and validity. We conclude that theories of reading comprehension processes also apply to some extent to the measurement of reading comprehension as a trainable skill and that the general factor score of the BYLET is suitable for a reading comprehension screening between grades two and six. The study is preregistered. The analysis code is available at https://osf.io/xw9bv/?view_only=21549993ef79426eb4006ef82415f25c . Test materials can be sent to interested researchers on request.

Where Dust Comes From: Global Assessment of Dust Source Attributions With AeroCom Models

AbstractThe source of dust in the global atmosphere is an important factor to better understand the role of dust aerosols in the climate system. However, it is a difficult task to attribute the airborne dust over the remote land and ocean regions to their origins since dust from various sources are mixed during long‐range transport. Recently, a multi‐model experiment, namely the AeroCom‐III Dust Source Attribution (DUSA), has been conducted to estimate the relative contribution of dust in various locations from different sources with tagged simulations from seven participating global models. The BASE run and a series of runs with nine tagged regions were made to estimate the contribution of dust emitted in East‐ and West‐Africa, Middle East, Central‐ and East‐Asia, North America, the Southern Hemisphere, and the prominent dust hot spots of the Bodélé and Taklimakan Deserts. The models generally agree in large scale mean dust distributions, however models show large diversity in dust source attribution. The inter‐model differences are significant with the global model dust diversity in 30%–50%, but the differences in regional and seasonal scales are even larger. The multi‐model analysis estimates that North Africa contributes 60% of global atmospheric dust loading, followed by Middle East and Central Asia sources (24%). Southern hemispheric sources account for 10% of global dust loading, however it contributes more than 70% of dust over the Southern Hemisphere. The study provides quantitative estimates of the impact of dust emitted from different source regions on the globe and various receptor regions including remote land, ocean, and the polar regions synthesized from the seven models.

Mechanisms and risk factors associated with spinal cord injury, facet fracture, and level of dislocation, in occupants with cervical spine dislocations sustained in motor vehicle crashes

Objective Motor vehicle crashes (MVCs) are the leading cause of cervical spine dislocation. The mechanisms underlying this injury are unclear, limiting the development of injury prevention devices and strategies. MVC databases contain occupant, medical, vehicle, and crash details that are not routinely collected elsewhere, providing a unique resource for investigating injury mechanisms and risk factors. In this study, a comprehensive standalone analysis of cervical spine dislocations captured in MVC databases was performed. Methods Epidemiologic, biomechanical, and injury data were extracted from three MVC databases. Logistic regression models were developed to determine the occupant, vehicle, and crash characteristics, as well as the global (inertial or impact) and regional (flexion, compression, etc.) loading mechanisms associated with the level of cervical spine dislocation (axial or sub-axial), and the occurrence of spinal cord injury (SCI) or facet fracture concomitant to dislocation. Results There was no association between global or regional injury mechanisms and the level of cervical spine dislocation. Sub-axial dislocations were typically due to head/face impact with the airbag or upper interior components, or a result of seatbelt restraint of the torso. Higher occupant age, lower BMI, partial/no ejection, and frontal and side configuration crashes (compared to rollovers) were associated with a higher likelihood of sub-axial, versus axial, dislocation. Amongst all dislocations, an increased likelihood of SCI was associated with impact injuries, airbag non-deployment, and complete ejection, while concomitant facet fracture was associated with the presence of regional compression. Severe crashes, partial ejections, and “utility vehicles” and “vans and trucks” (compared with “passenger vehicles”) were associated with a higher risk of facet fracture concomitant to sub-axial dislocation. Conclusion The findings of this study may be used to inform the loading modes to be simulated in future ex vivo or computational models seeking a better understanding of cervical spine dislocations.

Statistical characterization of specimen size and temperature dependence of cleavage fracture toughness of ferritic steels

AbstractBased on the numerical results on the non‐linear correlation between volume of plastic zone and global loading level represented by stress intensity factor, the dependence of cleavage fracture toughness of ferritic steels on specimen size and temperature is evaluated based on an empirical statistical model. The statistical correlation is supported by two sets of toughness data measured from different sized compact tension specimens at different temperatures. To further improve the accuracy of the statistical model, future work is identified to quantify the variation of volume of plastic deformation zone with loading level and measure the average volume for each microcrack at different temperature.

Historical footprints and future projections of global dust burden from bias-corrected CMIP6 models

Dust aerosols significantly affect the Earth’s climate, not only as a source of radiation, but also as ice nuclei, cloud condensation nuclei and thus affect CO2 exchange between the atmosphere and the ocean. However, there are large deviations in dust model simulations due to limited observations on a global scale. Based on ten initial Climate Models Intercomparison Project Phase Six (CMIP6) models, the multi-model ensemble (MME) approximately underestimates future changes in global dust mass loading (DML) by 7–21%, under four scenarios of shared socioeconomic pathways (SSPs). Therefore, this study primarily constrains the CMIP6 simulations under various emission scenarios by applying an equidistant cumulative distribution function (EDCDF) method combined with the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA2) datasets based on observation assimilation. We find that the results (19.0–26.1 Tg) for 2000–2014 are closer to MERRA2 (20.0–24.8 Tg) than the initial simulations (4.4–37.5 Tg), with model deviation reduced by up to 75.6%. We emphasize that the DML during 2081–2100 is expected to increase significantly by 0.023 g m–2 in North Africa and the Atlantic region, while decreasing by 0.006 g m–2 in the Middle East and East Asia. In comparison with internal variability and scenario uncertainty, model uncertainty accounts for more than 70% of total uncertainty. When bias correction is applied, model uncertainty significantly decreases by 65% to 90%, resulting in a similar variance contribution to internal variability.

Reinforcement Learning-Based Integrated Control to Improve the Efficiency of DC Microgrids

The hierarchical control of the DC microgrid regulates the terminal voltages of the interfacing converter to achieve proportional load sharing and good voltage regulation at the DC bus. In doing so, the difference of the voltage at different nodes increases which results in higher circulating current and leads to higher losses. In this paper, a Reinforcement Learning Based Integrated Control (RLIC) is proposed which will minimize the circulating current and power losses in the transmission. The proposed RLIC consists of a primary and secondary controller. The primary controller is a robust sliding mode controller which receives the voltage references from secondary controller and regulates the terminal voltage and source current accordingly. The secondary control consists of a proportional integral control (PI), and a Deep Neural Network (DNN) surrogate model with implementation of Q-Learning as reinforcement method. A novel DNN based surrogate model uses the droop value from the PI controller and estimates the power loss and the local and global loading difference for a particular node, for a set of operating condition. This surrogate model is used by the Q-Learning based reinforcement technique which adjusts the droop constants and provide the voltage reference to primary controller to maintain load sharing and reduce the power losses, there-by leading to an improved overall efficiency. The proposed control structure is verified to improve efficiency while maintaining the load sharing and bus voltage regulation.

Comparison of two semi‐quantitative amyloid PET analysis methods with and without MRI in Alzheimer’s Disease Spectrum Disorder

AbstractBackgroundStandardized uptake value ratio (SUVR) is a standard method for amyloid PET analysis. 3D T1 MRI imaging is required for accurate spatial normalization in SUVR measurement to overcome regional cortical atrophy in neurodegenerative disorders like Alzheimer’s disease spectrum disorders. The SUVR method without 3D MRI has recently been developed for clinical application. We compared two SUVR methods with and without 3D MRI for the semi‐quantitative analysis of global and regional amyloid loading in Alzheimer’s disease spectrum disorders.Method75 subjects (normal cognition 8, subjective cognitive decline 20, mild cognitive impairment 23, Alzheimer’s disease dementia 24) were selected in the single dementia clinic for the analysis. For the SUVR measurement with 3D T1 MRI, in‐house software with SPM8 and MATLAB was used. For the SUVR measurement without 3D T1 MRI, AI‐based automated PET quantitative analysis software (called ‘BTXBrain‐Amyloid‐Research’) was developed by Brightonix Imaging Inc. With the visual PET reading as a gold standard, we compared regional and global SUVR between groups. Intra‐class correlation coefficient(ICC) was used to test the validity of the two methods.ResultGlobal SUVR was higher in amyloid PET positive SCD group (SUVR with MRI (1.205 V.S. 1.635), SUVR without MRI (1.210 V.S. 1.599)). The mean global SUVR with MRI and without MRI of 75 subjects were 1.400 (S.D. 0.264) and 1.390(S.D. 0.237). ICC of global SUVR between the two methods was 0.950, p = 0.0001. Regional SUVR ICC were 0.941 in the prefrontal cortex, 0.953 in the orbitofrontal cortex, 0.947 in the anterior cingulate, 0.844 in the posterior cingulate, 0.955 in the lateral parietal cortex, 0.962 in the precuneus, 0.959 in the lateral temporal cortex, and 0.94 in the occipital cortex. The area under the curve of ROC curve analysis of both two methods to diagnose amyloid PET positivity was 0.98 and 0.97.ConclusionAI‐based automated PET quantitative analysis software of Brightonix imaging without MRI was valid as an MRI‐based SUVR method in Alzheimer’s disease spectrum disorders with variable brain atrophy. Short processing time (30 ‐40 seconds) and reliable SUVR measurement without 3D MRI benefit the Alzheimer’s disease diagnosis in clinical practice.Grant from the Ministry of Health and Welfare, HI18C0530, Seoul R&amp;BD Program(BT200151)

Reliability analysis of gas pipelines under global bending and thermal loadings considering a high chloride ion environment

The long-distance gas pipelines inevitably experience global bending deformation due to the ground movements. Meanwhile, a harsh environment where both the temperature may change drastically and the high chloride ion soil condition possibly causes more severe corrosion on the pipelines, could pose a significant challenge to pipeline safety. It is very crucial to ensure gas pipeline safety and durability in the energy transportation industry. Therefore, this study aims to systematically investigate the failure pressure of corroded gas pipelines under the combined effects of global bending and temperature difference. Considering gas pipelines potentially exposed to soil conditions with different contents of sodium chloride (NaCl), five corrosion rate models were for the first time employed to carry out reliability-based lifetime prediction analysis. The results show that compared to the case without global bending and temperature difference, the service life of gas pipelines can be reduced by 14 % in the case of global bending strain of 0.25 % and temperature difference of −40 °C. As for the corrosion rate model, the Model 4 plays a strongly adverse role in the service life of gas pipelines. Furthermore, parametric sensitivity analysis indicates that apart from the working pressure, initial corrosion depth and the radial corrosion rate are the two more influential factors in affecting the service life of gas pipelines.

Modeling of a Slope Reinforced by an Anchored Geomat System to Investigate Global Loading Behavior and Slope Stability

Modeling of a Slope Reinforced by an Anchored Geomat System to Investigate Global Loading Behavior and Slope Stability

Multi-model ensemble projection of the global dust cycle by the end of 21st century using the Coupled Model Intercomparison Project version 6 data

Abstract. As a natural aerosol with the largest emissions on land, dust has important impacts on the atmospheric environment and climate systems. Both the emissions and transport of dust aerosols are tightly connected to meteorological conditions and as a result are confronted with strong modulations by the changing climate. Here, we project the changes in the global dust emissions and loading by the end of the 21st century, using an ensemble of model outputs from the Coupled Model Intercomparison Project version 6 (CMIP6) under four Shared Socioeconomic Pathways (SSPs). Based on the validations against site-level observations, we select 9 out of 14 models and estimate an ensemble global dust emissions of 2566 ± 1996 Tg a−1 (1 Tg = 1012 g) for the present day, in which 68 % is dry deposited and 31 % is wet deposited. Compared to 2005–2014, global dust emissions show varied responses, with a reduction of −5.6 ± 503 Tg a−1 under the SSP3–7.0 scenario but increased emissions up to 60.7 ± 542 Tg a−1 under the SSP5–8.5 scenario at 2090–2099. For all scenarios, the most significant increase in the dust emissions appears in North Africa (0.6 %–5.6 %) due to the combined effects of reduced precipitation but strengthened surface wind. In contrast, all scenarios show decreased emissions in the Taklimakan and Gobi deserts (−0.8 % to −11.9 %) because of the increased precipitation but decreased wind speed on a regional scale. The dust loading shows uniform increases over North Africa (1.6 %–13.5 %) and the downwind Atlantic, following the increased emissions but decreases over East Asia (−1.3 % to −10.5 %), and the downwind Pacific, partly due to enhanced local precipitation that promotes wet deposition. In total, global dust loading will increase by 2.0 %–12.5 % at the end of the 21st century under different climate scenarios, suggesting a likelihood of strengthened radiative and climatic perturbations by dust aerosols in a warmer climate.

Statistical analyses of the relationship between inclination angle and twin growth in uniaxial compression of Mg alloys

Inclination angle (IA), which is that between the c-axis of a twin and the global loading direction, satisfactorily captures trends observed in area fractions of both Schmid and non-Schmid twins. The detailed analyses also show that the non-Schmid twins form preferentially in smaller grains compared to that of Schmid ones.

A Review of Blast Loading in the Urban Environment

Urban blasts have become a significant concern in recent years. Whilst free-field blasts are well understood, the introduction of an urban setting (or any complex geometry) gives rise to multiple blast wave interactions and unique flow complexities, significantly increasing the difficulty of loading predictions. This review identifies commonly agreed-upon concepts or behaviours that are utilised to describe urban shock wave propagation, such as channelling and shielding, in conjunction with exploring urban characterisation metrics that aim to predict the effects on global blast loading for an urban blast. Likewise, discrepancies and contradictions are highlighted to promote key areas that require further work and clarification. Multiple numerical modelling programmes are acknowledged to showcase their ability to act as a means of validation and a preliminary testing tool. The findings contained within this review aim to inform future research decisions and topics better.

Fatigue of short carbon fiber reinforced PEEK under compression: Influence of the load ratio and predictions from heat buildup measurements

AbstractFew works investigate the fatigue of short fiber reinforced thermoplastics under cyclic compression. Furthermore, the heat buildup approach to quickly predict the fatigue lifetime of these materials has not yet been investigated for compression–compression loadings. This paper first describes an experimental protocol to perform well‐controlled cyclic compression tests without anti‐buckling device that may induced bias. The uniaxiality of the global loading is checked during the test based on kinematic and thermoelastic coupling field measurements. Then, the paper compares the results from fatigue and heat buildup tests performed on polyetheretherketone reinforced with 30 wt% of short carbon fibers for several load ratios. It is shown that the fatigue lifetime is higher in compression than in tension and depends on the compression load ratio. The heat buildup approach appears to be relevant to quickly predict the fatigue lifetime of the material for the different loading ratios studied, including compression–compression.

Use of fly ash as synergistic and reactive component of flame retardant system in polylactide

For a long time, fly ash has been considered as pure waste of coal power plants. Nevertheless, unique properties and compositions that vary with the material's origin make fly ash appealing as an engineering material in various applications. Thus, the opportunity to reduce the environmental footprint of polylactide through the incorporation of fly ash as a component of flame retardant systems has been investigated. Combinations of fly ash with ammonium polyphosphate and/or melamine polyphosphate were made for a global loading of 25 wt% with various rates of substitution of the flame retardants. Fire performance has been studied from cone calorimeter experiments as well as the use of pyrolysis combustion flow calorimeter (PCFC) and the UL94V test. The interpretation of the fire retardant mechanisms has been performed through the examination of cone calorimeter residues by scanning electronic microscopy, X-ray microanalysis, X-ray diffraction (XRD) and multinuclear solid-state NMR. It can be shown that fly ash is mainly composed of spherical particles which are thermally stable at cone calorimeter tests when used alone in PLA. Conversely, fly ash behaves as a reactive component with both flame retardants, leading to the formation of new crystalline and amorphous compounds as shown by XRD and NMR. Synergistic effects in fire performance resulting from the reactive behavior of fly ash can be highlighted and are ascribed to fire retardant mechanisms acting in the condensed phase, and corresponding to the conservation of high phosphorus contents in the condensed phase.

Constraints on Secular Geocenter Velocity From Absolute Gravity Observations in Central North America: Implications for Global Melting Rates

AbstractLong series of absolute gravity observations at multiple sites provide a direct method of measuring the velocity of the geocenter caused by surface mass transport related to climate change. Annual absolute gravity observations and available GPS vertical data at eight sites in central North America from 1995 to 2010 are used to solve for geocenter velocity while correcting for glacial isostatic adjustment. The precision of the secular gravity trends and GPS heights at our sites, used to estimate geocenter motion, was improved by correcting for local and global water storage attraction and loading. Corrections for the loading and attraction effects of regional ice‐mass loss, the atmosphere and non‐tidal ocean were found to be minimal. Our results provide a direct measurement of the change in geocenter velocity over the time‐interval 2002–2010 compared to the time‐interval 1995–2003 of 0.68 ± 0.28 mm/yr away from North America. This suggests similar velocities in the negative Z (0°N) and positive Y (90°E) directions to those found by other studies.

Mineral dust aerosol impacts on global climate and climate change

Mineral dust aerosols impact the energy budget of Earth through interactions with radiation, clouds, atmospheric chemistry, the cryosphere and biogeochemistry. In this Review, we summarize these interactions and assess the resulting impacts of dust, and of changes in dust, on global climate and climate change. The total effect of dust interactions on the global energy budget of Earth — the dust effective radiative effect — is −0.2 ± 0.5 W m−2 (90% confidence interval), suggesting that dust net cools the climate. Global dust mass loading has increased 55 ± 30% since pre-industrial times, driven largely by increases in dust from Asia and North Africa, leading to changes in the energy budget of Earth. Indeed, this increase in dust has produced a global mean effective radiative forcing of −0.07 ± 0.18 W m−2, somewhat counteracting greenhouse warming. Current climate models and climate assessments do not represent the historical increase in dust and thus omit the resulting radiative forcing, biasing climate change projections and assessments of climate sensitivity. Climate model simulations of future changes in dust diverge widely and are very uncertain. Further work is thus needed to constrain the radiative effects of dust on climate and to improve the representation of dust in climate models. Dust influences the global energy budget through various Earth system interactions. This Review outlines these interactions, revealing a total radiative effect of −0.2 ± 0.5 W m−2, which, alongside 55 ± 30% historical increases in dust, have contributed a radiative forcing of −0.07 ± 0.18 W m−2.

Atypically Intense and Delayed Response of the Martian Ionosphere to the Regional Dust Storm of 2016: A Study Using MAVEN Observations and Models

AbstractDuring Mars dust storms, atmospheric heating and expansion moves the ionospheric peak upward. Typically, peak altitude increases by no more than 10 km, and this increase occurs simultaneously with the expansion of the dust storm. However, Felici et al. (2020), https://doi.org/10.1029/2019JA027083, using the Mars Atmosphere Volatile EvolutioN (MAVEN) Radio Occultation Science Experiment (ROSE), reported an unusually large increase of ∼20 km at southern latitudes in early October 2016 during a modest dust storm. Here, we investigate why the ionospheric peak altitude increased so much in these observations. We extend the time series of ionospheric peak altitude values beyond the limited extent of the ROSE observations by applying a one‐dimensional photochemical model, in which neutral atmospheric conditions are based on in situ MAVEN Neutral Gas Ion Mass Spectrometer observations at similar latitudes and solar zenith angles to those observed by ROSE. We find that the ionospheric peak altitude was highest throughout October 2016 yet both the local and global atmospheric dust loading were greatest 1 month earlier. We hypothesize that (a) a portion of the unusually large 20 km enhancement in peak altitude and (b) the unusual delay between the greatest dust loading and the highest peak altitude were both associated with the occurrence of perihelion, which maximizes solar heating of the atmosphere, in late October 2016.