Residual Analysis Research Articles

Multiobjective optimization of welding process variables in RMD and FCAW techniques using a heat transfer search algorithm for 316LN stainless steel

This study aims to identify the optimal parameters for regulated metal deposition (RMD) and flux-cored arc welding (FCAW) processes when joining 316LN stainless steel. The objective was to determine the optimal settings for current (A), voltage (V), and gas flow rate (GFR, L/min) to achieve the desired weld bead characteristics, including bead width (BW), bead height (BH), depth of penetration (DOP), and heat-affected zone (HAZ). A Box–Behnken design based on response surface methodology was employed for the bead-on-plate trials. Mathematical models were developed from the experimental data and validated through analysis of variance and residual analysis, with R-squared values confirming model accuracy. The heat transfer search (HTS) algorithm was used for both single objective and multiobjective optimization. For RMD, optimal results were achieved with a BW of 9.95 mm, BH of 4.39 mm, DOP of 2.26 mm, and HAZ of 0.29 mm, at 130 A, 18 V, and 20 L/min GFR. For FCAW, optimal values were a BW of 11.45 mm, BH of 3.59 mm, DOP of 2.15 mm, and HAZ of 0.40 mm, at 210 A, 24 V, and 10 L/min GFR. The Pareto solutions offered a most suitable choice of the optimal configuration, balancing the desired BW, BH, DOP, and HAZ values. The effectiveness of the HTS algorithm is demonstrated by the minimal differences between predicted and measured values, highlighting its high accuracy in optimizing 316LN stainless steel welding parameters.

Long-term variations in peak electron density and temperature of mesopause region: Dependence on solar, geomagnetic, and atmospheric activities, long-term trends

The paper overviews the main results of the study of long-term variations in characteristics of the upper neutral atmosphere and ionosphere, obtained during the implementation of Russian Science Foundation Project No. 22-17-00146 “Experimental and theoretical study of the coupling neutral and ionized components of Earth’s atmosphere”. We study and compare long-term variations in the peak electron density and temperature of the mesopause region. Their dependences on solar, geomagnetic, and atmospheric activity, as well as long-term trends, are analyzed. The analysis is based on data from long-term measurements with the ISTP SB RAS complex of instruments. The peak electron density (NmF2) data was acquired with the Irkutsk analog automatic ionospheric station for 1955–1996 and the Irkutsk digital ionosonde DPS-4 for 2003–2021. The atmospheric temperatures at mesopause altitudes (Tm) were obtained from spectrometric observations of the hydroxyl molecule emission (OH (6-2) band, 834.0 nm, emission maximum height ~87 km) for 2008–2020. The analysis uses solar (F10.7) and geomagnetic (Ap) activity indices, as well as data on variations in the Southern Oscillation Index (SOI). The study employs simple and multiple linear regression methods. Annual average NmF2 values are found to be predominantly controlled by changes in solar flux. Analysis of regression residuals shows that the largest deviations from regression (for both simple and multiple regression) are observed in years near the maxima of solar cycles 19 (1956–1959) and 22 (1989–1991). Annual average temperature variability in the mesopause region correlates with changes in the SOI index: day-to-day variability exhibits a positive correlation with SOI; and intra-diurnal variability, a negative correlation with SOI. No significant relationship was found between year-to-year variations in the NmF2 and Tm variability.

Долговременные вариации максимума электронной концентрации и температуры области мезопаузы: зависимости от солнечной, геомагнитной и атмосферной активности, долговременные тренды

The paper overviews the main results of the study of long-term variations in characteristics of the upper neutral atmosphere and ionosphere, obtained during the implementation of Russian Science Foundation Project No. 22-17-00146 “Experimental and theoretical study of the coupling neutral and ionized components of Earth’s atmosphere”. We study and compare long-term variations in the peak electron density and temperature of the mesopause region. Their dependences on solar, geomagnetic, and atmospheric activity, as well as long-term trends, are analyzed. The analysis is based on data from long-term measurements with the ISTP SB RAS complex of instruments. The peak electron density (NmF2) data was acquired with the Irkutsk analog automatic ionospheric station for 1955–1996 and the Irkutsk digital ionosonde DPS-4 for 2003–2021. The atmospheric temperatures at mesopause altitudes (Tm) were obtained from spectrometric observations of the hydroxyl molecule emission (OH (6-2) band, 834.0 nm, emission maximum height ~87 km) for 2008–2020. The analysis uses solar (F10.7) and geomagnetic (Ap) activity indices, as well as data on variations in the Southern Oscillation Index (SOI). The study employs simple and multiple linear regression methods. Annual average NmF2 values are found to be predominantly controlled by changes in solar flux. Analysis of regression residuals shows that the largest deviations from regression (for both simple and multiple regression) are observed in years near the maxima of solar cycles 19 (1956–1959) and 22 (1989–1991). Annual average temperature variability in the mesopause region correlates with changes in the SOI index: day-to-day variability exhibits a positive correlation with SOI; and intra-diurnal variability, a negative correlation with SOI. No significant relationship was found between year-to-year variations in the NmF2 and Tm variability.

Residual Stress Analysis at the Conductor–Insulator Interface During the Curing Process of Hair-Pin Motors

The curing process of hair-pin motor stator insulation is critical, as residual stress increases the risk of partial discharge and shortens a motor’s lifespan. However, studies on the stress-induced defects during insulation varnish curing remain limited. This research integrates three-dimensional numerical simulations and experimental analysis to develop a curing model based on unsaturated polyester imide resin, aiming to explore the mechanisms of residual stress formation and optimization strategies. A dual fiber Bragg grating (FBG) sensor system is employed for simultaneous temperature and strain monitoring, while curing kinetics tests confirm the self-catalytic nature of the process and yield the corresponding kinetic equations. The multi-physics simulation model demonstrates strong agreement with the experimental data. The results show that optimizing the curing process reduces the maximum stress from 45.1 MPa to 38.6 MPa, effectively alleviating the stress concentration. These findings highlight the significant influence of the post-curing temperature phase on residual stress. The proposed model offers a reliable tool for stress prediction and process optimization in various insulating materials, providing valuable insights for motor insulation system design.

PHP-Family Diesterase from Novosphingobium with Broad Specificity and High Catalytic Efficiency against Organophosphate Flame-Retardant Derived Diesters.

Organophosphate flame retardants have been widely used in plastic products since the early 2000s. Unfortunately, these compounds leach out of the plastics over time and are carcinogenic, developmental toxins, and endocrine disruptors. Due to the high usage levels and stable nature of the compounds, widespread contamination of the environment has now been observed. Despite their recent introduction into the environment, bacteria from the Sphingomonadaceae family have evolved a three-step hydrolytic pathway to utilize these compounds. The second step in this pathway in Sphingobium sp. TCM1 is catalyzed by Sb-PDE, which is a member of the polymerase and histidinol phosphatase (PHP) family of phosphatases. This enzyme is only the second case of a PHP-family enzyme capable of hydrolyzing phosphodiesters. Bioinformatics analysis has now been used to identify a second PHP diesterase from Novosphingobium sp. EMRT-2 (No-PDE). Kinetic characterization of Sb-PDE and No-PDE with authentic organophosphate flame-retardant diesters demonstrates that these enzymes are true diesterases with more than 1000-fold selectivity for the diesterase activity seen in some cases. Synthesis of a wide array of authentic flame-retardant diesters has allowed the substrate specificity of these enzymes to be determined, and mutagenic analysis of the active site residues has identified key residues that give rise to the high levels of diesterase activity. Despite high sequence identity, No-PDE is found to have a broader substrate specificity against flame-retardant derived diesters, and kcat/Km values greater than 104 M-1 s-1 are seen with the best substrates.

Thermal and residual stress analysis of multi-pass welded stainless steel pipes using DEFLUX and FILM subroutine

This study presents an in-depth investigation of the influence of welding parameters (welding speed and number of passes) on the residual stress distribution in AISI 304 (Z7CN18-09) austenitic stainless-steel tubes. A three-dimensional finite element modeling (FEM), developed in ABAQUS, was implemented to simulate the circumferential welding process. The DFLUX and FILM subroutines were implemented to model the double ellipsoid mobile heat source and thermal boundary conditions, respectively. Model validation was performed by comparing weld bead profiles and thermal cycles with experimental results, showing excellent correlation (deviation < 5%). The coupled thermal and mechanical analyses allowed evaluation of the spatiotemporal evolution of the temperature field for different welding speeds (80-160-240 mm/min) and the distribution of axial and circumferential residual stresses as a function of tube thickness. The numerical results demonstrate a significant influence of these parameters on the amplitude and distribution of residual stresses, with a notable reduction in maximum stresses for optimized welding speeds and better stress homogenization with multi-pass welding.

Residue analysis and risk assessment of cyflumetofen and its three metabolites from fresh tea leaf to tea infusion through purification with new nano adsorbents and determination by ultra-performance liquid chromatography-tandem mass spectrometry

Residue analysis and risk assessment of cyflumetofen and its three metabolites from fresh tea leaf to tea infusion through purification with new nano adsorbents and determination by ultra-performance liquid chromatography-tandem mass spectrometry

The Behaviour of carbon quantum dots and cryogenic cooling in turning of super duplex F 53 steel

The objective of this research is to examine how various cooling and lubrication techniques affect the machinability of Duplex F53 steel when turning it, with particular attention to residual stress, surface roughness, chip morphology, tool wear, machining temperature, and crystallographic structures. According to the microstructure analysis, the presence of additional austenite grains at high temperatures during dry machining results in an increase in hardness. On the other hand, cooling techniques including liquid nitrogen (LN2), carbon Quantum dots with SQL (CD), and oil with small quantity lubrication (OSQL) produce larger ferrite grains, which lower hardness. According to residual stress analysis, the high temperatures during dry cutting result in increased strains, which are successfully mitigated by lubrication. The two-phase microstructure has a crucial influence in mechanical characteristics, as demonstrated by X-ray diffraction (XRD) studies, wherein finer grains improve surface polish but demand more energy. Measuring surface roughness (Ra) reveals that adhesion wears during dry machining raises Ra, while OSQL and LN2 cooling lower Ra and improve surface quality. Tool performance is negatively impacted by high machining temperatures. Cutting temperatures and friction are greatly reduced by LN2 cooling. Dry machining increases tool wear because of the high temperatures and absence of lubrication; OSQL and CD lower wear rates, while LN2 offers the best protection for tools. Thinner, better-separated chips are produced by effective lubrication in OSQL and LN2, while thicker, more deformed chips are produced by dry machining, according to chip morphology and thickness analyses. The study leads to the conclusion that super duplex steel's surface quality, tool life, and machinability can all be significantly enhanced by carbon quantum dots and cryogenic cooling.

Thermal and Computational Analysis of MHD Dissipative Flow of Eyring-Powell Fluid: Non-Similar Approach via Overlapping Grid-Based Spectral Collocation Scheme

The aim of the present study is to numerically investigate the non-similar flow and heat transfer in a dissipative Eyring-Powell fluid (EPF) over a stretching surface. A constant magnetic field is applied perpendicular to the stretched surface to explore the impact of the Lorentz force. Both viscous and magnetic dissipation are considered to comprehensively examine their effects on heat transfer. The problem in hand does not admit self-similar solutions as the non-Newtonian fluid parameter varies with the spatial variable along the stream-wise direction. Consequently, the set of nonlinear partial differential equations, modeling the flow problem is nondimensionalized primarily by employing a pseudo-similarity variable and stream-wise coordinate. The non-dimensional set of nonlinear partial differential equations is solved by a newly developed and efficient “overlapping multi-domain bivariate spectral local linearization method (OMD-BSLLM)”. The current study includes residual error analysis and convergence tests to demonstrate the accuracy of the numerical method applied to the current mathematical model. Graphs show fluid flow and heat transfer results for different flow parameters, while tables display skin friction and Nusselt number values. The results indicate that the non-Newtonian fluid parameter enhances both the velocity profile and temperature distribution. The fluid decelerates with increasing the dimensionless stream wise coordinate and Hartmann number. Viscous dissipation and dimensionless stream-wise coordinate enhances the temperature profile.

Residual analysis for the identification of potential MIR-derived biomarkers of heat stress in dairy cattle.

Numerous prediction equations have been developed based on mid-infrared (MIR) spectra and some could be potentially used as biomarkers of heat stress. However, practical experience shows that confusion between the effect of heat stress and other effects like lactation stage or feeding variation over the year can easily occur. On this basis, the objective of this study was to identify potential milk components predicted by MIR as biomarkers of heat stress based on a 2-step approach allowing to correct for those effects. The first step consisted in the estimation of residuals from test-day random regression models on days in milk (DIM) to remove systematic lactation stage effects. These models contained also, among other, general (i.e., month of production) or specific (i.e., herd × test-day (HTD)) fixed effects related to feeding and management. During the second step, means and variances of residuals by temperature and humidity index (THI) classes were studied. The models were applied to 611,063 records from 97,042 primiparous Holstein cows from 2015 to 2022 in the south of Belgium. The MIR-predicted milk components with the highest deviations from the mean with increasing THI were protein percentage, casein concentration, magnesium (Mg) concentration and, to a lesser extent, polyunsaturated fatty acid (PUFA) concentration. Concerning residual variances, the highest heteroscedasticity with THI was obtained for milk MIR monounsaturated fatty acid (MUFA), C18:1 cis-9 and citrate concentrations. Conversely, a relative homoscedasticity of variance with increasing THI was observed for several milk MIR components including protein percentage and casein concentration. Based on the criteria of the "good biomarkers" guidelines, milk protein percentage seems to be the most promising trait of this study, followed by Mg concentration. However, in the context of genetic evaluation which requires variability, milk MIR MUFA, C18:1 cis-9 or citrate concentration variations, if they are heritable, could be of great interest. Finally, an increase in milk MIR citrate concentration variance could be an early warning for the detection of heat stress in the frame of dairy herd improvement (DHI).

Metallacrown of CeIIICuII5: Synthesis, Structural Characterization and Insights for Nanoparticles

The heterobimetallic 15-MC-5 metallacrown of formula [CeCu5(5mpzHA)5(NO3)(H2O)7]·2NO3·7H2O, designated MC-Ce, was synthesized using 5-methyl-2-pyrazinehydroxamic acid (5mpzHA) as a linker, reacting with CeIII and CuII salts under mild conditions. Single-crystal X-ray diffraction analysis reveals a crown-like [Cu5Ce(5mpzHA)5] core, characteristic of a 15-MC-5 system, with five CuII atoms at the rim of the crown and the CeIII ion occupying the dome of the crown, with water molecules, oxygen atoms and one nitrate anion filling the nine-coordination sphere around the CeIII ion, which exhibits a distorted spherical tricapped trigonal prism geometry. The thermogravimetric analysis evidences successive mass losses due to the removal of water molecules and decomposition of the structure after 217 °C, whereas the PXRD analysis of the thermal decomposition residue reveals the presence of copper and copper/cerium oxide particles. These nanocomposite materials were also synthesized using the metallacrown MC-Ce under a hydrothermal method in the presence of multi-walled carbon nanotubes (MWCNTs), affording insights that this metallacrown can act as a source precursor for the synthesis of these mixed cerium/copper oxide nanomaterials. The experimental χMT value in MC-Ce at room temperature is 3.175 cm3 mol−1 K, which is higher than the calculated one for one magnetically isolated CeIII plus five CuII ions, probably due to the antiferromagnetic interactions among CuII ions within the metallacrown hoop plus the thermal depopulation of JZ sublevels of CeIII ground state (5/2), which exhibit a small splitting under the anisotropic ligand field effects. The χMT decreases continuously until it reaches the value of 0.80 cm3 mol−1 K at 10 K, reinforcing the presence of intramolecular antiferromagnetic interactions.

Detecting overfitting by examining residuals in autoregressive models

The aim of this study is to see how overfitting can be detected using non-rigorous analysis of residuals. The well-known statistical packages was used to simulate data from stationary autoregressive models with Gaussian white noise with mean 0 and variance one. In order to see the effect of realization size on our findings, the sample size 50 was used as an example of small realization and the sample size 500 was used as an example of large realization. The method of maximum likelihood was used in the fitting of autoregressive models to the simulated data which is available in the statistical package R. Interesting and promising results were obtained. Our study seems to suggest that comparing estimates with their standard errors is the only reliable criterion in spotting or detecting overfitting. To make sure that the defect in the behavior of the residuals is due only to the over, we used only the same class of models in the simulation and the fitting.

Preparation of Nitrogen‐Phosphorus‐Silicon Synergistic Intumescent Flame Retardant and Its Effect on the Flame Retardancy of Waterborne Polyurethane

ABSTRACTWaterborne polyurethane is widely used across various industries, including construction, automotive, leather, and thermal insulation, due to its exceptional properties such as lightweight, thermal insulation, and corrosion resistance. However, its susceptibility to combustion significantly limits its utility, highlighting the critical need for integrating flame retardants into polyurethane formulations. This study focuses on the synthesis of a novel hyperbranched flame retardant, HBNPSi, achieved by manipulating the proportions of 10‐(2′,5′‐dihydroxyphenyl)‐9,10‐dihydro‐9‐oxa‐10‐phospha‐phenanthrene‐10‐oxide (DOPO‐BQ), 1,3,5‐trihydroxyethylcazinone (THC), and isocyanatopropyltrihydroxyethylsilane (IPTS) as the constituent materials. The structural characteristics of the flame retardant were analyzed using infrared spectroscopy, carbon residue analysis, swelling height measurements, and x‐ray spectroscopy (EDS). HBNPSi was then incorporated as a reactive monomer in the pre‐polymerization reaction of aqueous polyurethane to produce a hyperbranched flame‐retardant polyurethane. The flame‐retardant properties were assessed through various tests, including oxygen index, vertical and horizontal combustion, thermo‐red in‐line, and cone calorimetry. Notably, the introduction of DOPO as a flame retardant in a ratio of BQ:THC = 2:1 resulted in an oxygen index of 29% and achieved a V‐0 flame‐retardant rating. Additionally, the decomposition temperature increased from 250°C to 300°C, while the heat release rate (HRR) decreased by 47.8%, total heat release (THR) decreased by 28.2%, and total smoke production (TSP) was reduced by 46.2%.

Groundwater flow system of the Abijata-Langano-Ziway lakes basin, Ethiopia

The Abijata-Langano-Ziway Lakes Basin (ALZLB) is situated in the Central part of the Main Ethiopian Rift. The availability and dynamics of groundwater in the Abijata-Langano-Ziway Lakes Basin (ALZLB) are primarily controlled by its geological and hydrogeological characteristics, shaped by volcanic-tectonic and sedimentary processes. The basin faces significant challenges, including drastic change in land use pattern, rapid population growth sustained by subsistence farming, over-extraction of water resources, and vulnerability to climate change and fragile ecosystems. These issues emphasize the urgent need for effective water resource management.To understand this complex system, a numerical groundwater flow model was employed to characterize the groundwater flow system within the ALZLB and examine its interaction with surface water bodies. The MODFLOW model translates the conceptual understanding of the basin's hydrogeology into a mathematical representation, allowing for numerical analysis. The model incorporates input parameters such as hydraulic conductivity and boundary conditions representing groundwater inflow and outflow. Steady-state numerical calculation was used to characterize the qualitative hydrogeological conceptual model into numerical representation and thereby describe the groundwater system.The calibrated model exhibited excellent agreement between simulated and observed groundwater levels. Statistical measures indicated a strong correlation (R2 = 0.98) and high efficiency (NSE = 0.97) in replicating the observed data. Additionally, the Mean Error (ME) of −8.3 m suggests minimal bias in the simulations. Further analysis of the histogram residuals revealed that a significant portion of the simulated values (65 % and 82 %) fell within ±20 m and ±30 m of the observed groundwater levels, respectively. This revealed the model's accuracy in capturing the groundwater system's behavior.The model identified groundwater recharge and constant head boundaries as the primary sources of groundwater inflow, contributing 445 million cubic meters per year (MCM/year) and 90 MCM/year, respectively. Conversely, constant head boundaries represented the most significant outflow pathway, with a simulated discharge of 519 MCM/year. The calibrated balance between inflow and outflow (discrepancy of −0.75 %) confirms that the model effectively simulates steady-state groundwater flow conditions. The calibrated model demonstrates the model's capability to accurately represent the basin's groundwater system.

Evaluating the culinary significance of maize in the Araucanía, Southern Chile: Evidence from organic residue analysis of pre-colonial pottery

Maize, one of the primary crops cultivated in South America, has achieved significant interest in regional archaeology. However, the study of maize in regions considered peripheral to major centres of agricultural production, such as Southern Chile, has received minimal attention. Southern Chile is the southernmost point for the dispersal of maize cultivation in the Americas, with archaeological evidence dating back ca. 1000 CE. Despite the manifest presence of maize, our knowledge of its culinary and economic importance for pre-colonial societies from Southern Chile is scarce. In this study, we extracted and analysed organic residues from 188 pottery sherds to explore the potential significance of maize in local foodways over the transition from the Early (ECP: 400–1000 CE) to the Late (LCP: 1000–1550 CE) Ceramic Period. Biomolecular and carbon-stable isotope (δ13C) analyses of lipids indicate that maize was not a staple. Instead, our findings suggest that maize had a potentially prominent role in preparing fermented beverages consumed in important socio-political gatherings and feasts.

Increases in vegetation cover increase response more to climate change than to human activities in the Baiyangdian watershed

Abstract Baiyangdian watershed is located in the upstream of Xiongan New Area, and as an important ecological source of the new area, its vegetation cover status has an important impact on the environmental quality and ecological health of the new area. By analysing the spatial and temporal characteristics of vegetation cover in the Baiyangdian watershed, we investigated the response of climate change and human activities to vegetation cover, and revealed the evolution patterns and driving mechanisms of vegetation cover under changing environments. Utilizing the Google Earth Engine (GEE) and Landsat remote sensing images, the normalized difference vegetation index (NDVI) of the Baiyangdian watershed from 1992 to 2022 was extracted. The temporal and spatial characteristics of vegetation cover were determined using Theil-Sen Median and Mann-Kendall analysis, while factors influencing the spatiotemporal changes in vegetation cover in Baiyangdian were explored through correlation and residual analyses reveal the following: (1) Vegetation cover in the study area showed an increasing trend over time, with a spatial increase from northwest to southeast, revealing the recovery of the ecological environment; (2) Vegetation cover was positively correlated with precipitation and temperature, and the effect of temperature on Baiyangdian was greater than that of precipitation; (3) Residual analyses showed that human activities and climate change had an increasing role in contributing to vegetation cover, and that the dominant factor had changed from human activities to climate changes. The residual analysis shows that human activities and climate change are increasing the vegetation cover, and the dominant factor is changing from human activities to climate change. This study provides a scientific basis for the ecological management of Baiyangdian and the construction of forestry engineering.

Mapping of Nuclear Localization Signal in Secreted Liver-Specific Protein 2 of Plasmodium falciparum.

The secretory proteome of Plasmodium exhibits differential spatial and functional activity within host cells. Plasmodium secretes proteins that translocate into the human host cell nucleus. Liver-specific protein 2 of Plasmodium falciparum (Pf-LISP2) shows nuclear accumulation in human hepatocytes during the late liver stage of malaria parasite development. However, the nuclear translocation mechanism for Pf-LISP2 remains largely uncharacterized. Here, we identified a classical bipartite nuclear localization signal (NLS) located in the C-terminal region of Pf-LISP2. Phylogenetic analysis revealed that this NLS is unique to Plasmodium falciparum and its close relative Plasmodium reichenowi, suggesting an evolutionary adaptation linked to their shared primate hosts. Functional assays confirmed the NLS's nuclear import activity, as fusion constructs of the Pf-LISP2 NLS with Pf-aldolase (Pf-aldolase-NLS-EGFP) localized exclusively to the nucleus of HepG2 cells. Mutation analysis of key lysine and arginine residues in the bipartite NLS demonstrated that the basic amino acid clusters are essential for nuclear localization. Importin-α/β interaction was found to be crucial for Pf-LISP2 nuclear transport, as coexpression of the NLS constructs with the importin-α/β inhibitor mCherry-Bimax2 significantly blocked nuclear translocation. Specific interactions between the lysine and arginine residues of Pf-LISP2's NLS and the conserved tryptophan and asparagine residues of human importin-α1 facilitate the cytosol-to-nuclear translocation of Pf-LISP2. Additionally, LISP2 lacks any nuclear export signal. These results provide new insights into the mechanisms of nuclear transport in Plasmodium falciparum, potentially contributing to the understanding of its pathogenicity and host-cell interactions during liver-stage infection.

Decoupling the Impacts of Climate Change and Human Activities on Terrestrial Vegetation Carbon Sink

Net ecosystem productivity (NEP) plays a vital role in quantifying the carbon exchange between the atmosphere and terrestrial ecosystems. Understanding the effects of dominant driving forces and their respective contribution rates on NEP can aid in the effective management of terrestrial carbon sinks, especially in rapidly urbanizing coastal areas where climate change (CC) and human activities (HA) occur frequently. Combining MODIS NPP products and meteorological data from 2000 to 2020, this paper established a Modis NPP-Soil heterotrophic respiration (Rh) model to estimate the magnitude of NEP in China’s coastal zone (CCZ). Hotspot analysis, variation trend, partial correlation, and residual analysis were applied to explore the spatiotemporal patterns of NEP and the contributions of CC and HA to the dynamics of NEP. We also explored the changes in NEP in different land use types. It was found that there is a clear north–south difference in the spatial pattern of NEP in CCZ, with Zhejiang Province serving as the main watershed for this difference. In addition, NEP in most regions showed an improvement trend, especially in the Beijing–Tianjin–Hebei region and Shandong Province, but the pixel values of NEP here were generally not as high as that in most southern provinces. According to the types of driving forces, the improvement of NEP in these regions primarily results from the synergistic effects of CC and HA. NEP changes in provinces south of Zhejiang are mainly dominated by single-factor-driven degradation. The area where HA contributes to the increase in NEP is much larger than that of CC. From the perspective of land use types, forests and farmland are the dominant contributors to the magnitude of NEP in CCZ.

Fabrication and Performance Investigation of Flame Retardant Flexible Polyurethane Composites via Polyethyleneimine/Phytic Acid LBL Self‐Assembly Coatings

ABSTRACTTo bolster the fire resistance of flexible polyurethane foam (FPUF), and a series of FPUF/polyethylenimine/phytic acid (FPUF/PEI/PA) composites were prepared by layer‐by‐layer self‐assembly strategy. Furthermore, the thermal stability, flame retardancy, combustion properties, and char layer were comprehensively evaluated via thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 vertical combustion test, microcalorimetry (MCC), scanning electron microscopy (SEM), Raman spectroscopy, and tensile testing. TG analysis revealed that the PEI/PA coatings markedly diminished the initial decomposition temperature (T‐5wt%) and char residue at 800°C. FPUF‐6 extended the burning duration by 20 s, a 80% improvement compared with unmodified FPUF, with an LOI value increased to 19.2 vol%. SEM and Raman analyses of the char residues indicated that the PEI/PA coating promoted graphitization degree of the char layer. This work offered novel insights for the development of high‐performance FPUF composites.

Improvement of Space-Observation of Aerosol Chemical Composition by Synergizing a Chemical Transport Model and Ground-Based Network Data

Aerosol chemical components are critical parameters that influence the atmospheric environment, climate effects, and human health. Retrieving global columnar atmospheric aerosol components from satellite observations provides foundational data and practical value. This study develops a method for retrieving aerosol component composition from polarized satellite data by synergizing a chemical transport model with ground-based remote sensing data. The method enables the rapid acquisition of columnar mass concentrations for seven aerosol components on a global scale, including black carbon (BC), brown carbon (BrC), organic carbon (OC), ammonium sulfate (AS), aerosol water (AW), dust (DU), and sea salt (SS). We first establish a remote sensing model based on the multiple solution mixing mechanism (MSM2) to obtain aerosol chemical components using AERONET ground-based measurements. We then employ a cross-layer adaptive fusion (CAF)-Transformer model to learn the spatial distribution characteristics of aerosol components from the MERRA-2 model. Furthermore, we optimize the retrieval model by transfer learning from the ground-based composition data to achieve satellite remote sensing of aerosol components. Residual analysis indicates that the retrieval model exhibits robust generalization capabilities for components such as BC, OC, AS, and DU, achieving a coefficient of determination of 0.7. Moreover, transfer learning effectively enhances the consistency between satellite retrievals and ground-based remote sensing results, with an average improvement of 0.23 in the correlation coefficient. We present annual and seasonal means of global distributions of the retrieved aerosol component concentrations, with a major focus on the spatial and temporal variations of BC and DU. Additionally, we analyze three typical atmospheric environmental cases, wildfire, dust storm, and particulate pollution, by comparing our retrievals with model data and other datasets. This demonstrates the ability of satellite remote sensing to identify the location, intensity, and impact range of environmental pollution events. Satellite-retrieved aerosol component data offers high spatial resolution and efficiency, particularly providing significant advantages for near-real-time monitoring of regional atmospheric environmental events.