Plateau Region Research Articles

Unrevealing the water-use strategies for typical ecological restoration plants and cash crops in the Eastern Chinese Loess Plateau region

Study regionFour geomorphic types in the eastern Loess Plateau (ECLP). Study focusquantitatively study the water-use strategies of typical plants (ecological restoration plants, food crops) based on stable isotope technology. New hydrological insights for the regionSignificant spatial-temporal heterogeneity appeared in regional soil water content and stable isotopes, with more significant fluctuations in soil water isotope values appearing in the rocky mountain region. Regional tree growth (including natural and plantation forests) was mainly influenced by precipitation (35±14 %) and surface layer (0–40 cm depth) soil water (25±11 %) during April and June, whereas deep soil water gradually became the main water source (> 20 %) in autumn and winter. A. Lavandulifolia mainly uses surface soil water (> 23 %), and the proportion of deep soil water utilization has increased after September. Surface soil water (0–40 cm) was the primary water source for T. aestivum during the overwintering (> 16 %) and reviving periods (> 26 %), and Z. mays utilized the largest proportion of soil water from 0 to 20 cm depth layer during the seeding (> 60 %) and maturation stages (> 35 %). Collectively, the results of this study have important implications for sustainable vegetation protection and the optimal allocation of water resources in the arid region.

Decoding China's new-type industrialization: Insights from an XGBoost-SHAP analysis

Integrating machine learning and explainable artificial intelligence offers superior interpretability for indicator selection compared with traditional evaluation models. This study utilizes the XGBoost-SHAP model to assess the influencing factors, development trends, and spatiotemporal evolution of China's new-type industrialization. The results demonstrate that digitalization emerges as the most critical factor, contributing 41.23% to the weight of indicators, followed by innovation drive at 34.31%, greenization at 16.38%, and aspects of servitization and fusion. China's new industrialization level shows a positive trend, with an accelerated growth rate post-2020, despite significant regional disparities in industrial indices. A spatiotemporal evolution identified a three-tier regional distribution: the eastern coastal, central plain, and western plateau regions. Notably, the improvement in new-type industrialization has expanded from coastal to inland regions, with significant progress observed in the southwestern region, represented by Sichuan Province. Additionally, the analysis revealed that China's level of new industrialization is converging toward the Hu Huanyong Line, suggesting that it may be influenced by population distribution density and natural environmental factors. The research results provide a scientific basis and decision-making guidance for evaluating the dynamics of China's new industrialization.

Environmental Driving of Adaptation Mechanism on Rumen Microorganisms of Sheep Based on Metagenomics and Metabolomics Data Analysis.

Natural or artificial selection causes animals to adapt to their environment. The adaptive changes generated by the rumen population and metabolism form the basis of ruminant evolution. In particular, the adaptive drive for environmental adaptation reflects the high-quality traits of sheep that have migrated from other places or have been distant from their origins for a long time. The Hu sheep is the most representative sheep breed in the humid and low-altitude environments (Tai Lake region) in East Asia and has been widely introduced into the arid and high-altitude environments (Tibetan Plateau and Hotan region), resulting in environmental adaptive changes in the Hu sheep. In this study, a joint analysis of the rumen microbial metagenome and metabolome was conducted on Hu sheep from different regions (area of origin and area of introduction) with the objective of investigating the quality traits of Hu sheep and identifying microorganisms that influence the adaptive drive of ruminants. The results demonstrated that the growth performance of Hu sheep was altered due to changes in rumen tissue and metabolism following their introduction to the arid area at relatively high altitude. Metagenomic and metabolomic analyses (five ramsper area) revealed that 3580 different microorganisms and 732 different metabolites were identified in the rumen fluid of arid sheep. Among these, the representative upregulated metabolites were 4,6-isocanedione, methanesulfonic acid and N2-succinyl-L-arginine, while the dominant microorganism was Prevotella ruminicola. The downregulated metabolites were identified as campesterol, teprenone and dihydroclavaminic acid, while the disadvantaged microorganisms were Dialister_succinatiphilus, Prevotella_sp._AGR2160, Prevotella_multisaccharivorax and Selenomonas_bovis. The results of the Pearson analysis indicated that the rumen microbiota and metabolite content of sheep were significantly altered and highly correlated following their relocation from a humid lowland to an arid upland. In particular, the observed changes in rumen microorganisms led to an acceleration of body metabolism, rendering sheep highly adaptable to environmental stress. Prevotella_ruminicola was identified as playing an important role in this process. These findings provide insights into the environmental adaptation mechanisms of sheep.

Impact of typical environments in China's western mountainous areas on the durability of railway concrete: a review

PurposeThis study aims to analyze the impact mechanism of typical environments in China's western mountainous areas on the durability of railway concrete and propose measures to improve durability.Design/methodology/approachWith the continuous promotion of infrastructure construction, the focus of China's railway construction has gradually shifted to the western region. The four typical environments of large temperature differences, strong winds and dryness, high cold and low air pressure unique to the western mountainous areas of China have adverse effects on the durability of typical railway structure concrete (bridges, ballastless tracks and tunnels). This study identified the characteristics of four typical environments in the western mountainous areas of China through on-site research. The impact mechanism of the four typical environments on the durability of concrete in different structural parts of railways has been explored through theoretical analysis and experimental research; Finally, a strategy for improving the durability of railway concrete suitable for the western mountainous areas of China was proposed.FindingsThe daily temperature difference in the western mountainous areas of China is more than twice that of the plain region, which will lead to significant temperature deformation and stress in the multi-layered structure of railway ballastless tracks. It will result in cracking. The wind speed in the western plateau region is about 2.5 to 3 times that of the plain region, and the average annual rainfall is only 1/5 of that in the plain region. The drying effect on the surface of casting concrete will significantly accelerate its cracking process, leading to serious durability problems. The environmental temperature in the western mountainous areas of China is generally low, and there are more freeze-thaw cycles, which will increase the risk of freeze-thaw damage to railway concrete. The environmental air pressure in the western plateau region is only 60% of that in the plain region. The moisture inside the concrete is more likely to diffuse into the surrounding environment under the pressure difference, resulting in greater water loss and shrinkage deformation of the concrete in the plateau region. The above four issues will collectively lead to the rapid deterioration of concrete durability in the western plateau region. The corresponding durability improvement suggestions from theoretical research, new technology development and standard system was proposed in this paper.Originality/valueThe research can provide the mechanism of durability degradation of railway concrete in the western mountainous areas of China and corresponding improvement strategies.

Effect of prefatigue-induced persistent slip bands on the strength-ductility match in -oriented Cu single crystals

To explore the effect of persistent slip bands (PSBs) formed during cyclic loading on the static mechanical behavior of materials, [1‾12]-oriented Cu single crystals are selected as target materials, and the tensile behavior of Cu single crystals prefatigued to the stress saturation stage at different plastic shear strain amplitudes (γpl) and the corresponding microstructures, surface deformation features and fracture morphologies are systematically studied. The results show that the formation of few soft PSB ladder-like structures in hard dislocation veins during prefatigue deformation at γpl = 3.7 × 10−4 below the plateau region of cyclic stress-strain (CSS) curve can promote a synchronous improvement of strength and ductility (SISD) compared with the unfatigued crystal. As γpl increases to a lower value of 9.0 × 10−4 within the plateau region, the strength and ductility reduce sharply compared with the case at γpl = 3.7 × 10−4 due to more concentrated plastic deformation caused by a high volume fraction of prefatigue-induced PSBs. With continuously increasing γpl to a higher value of 2.3 × 10−3 within the plateau region, non-uniform dislocation distribution in labyrinth structures and the short spacing between labyrinth walls as well as the fine dislocation cells formed during tension jointly give rise to a slight increase in strength and ductility compared with the crystal prefatigued at γpl = 9.0 × 10−4. As γpl is increased to the level beyond the plateau region, the ductility and ultimate tensile strength continuously increase, resulting from the co-existence of wider deformation bands and dense dislocation walls.

Cell structure development during cyclic deformation of near-[001] and near-[011] copper single crystals

Dislocation cell structures significantly influence the fatigue failure process. Research on the cell structures in multiple-slip-oriented copper single crystals has focused primarily on the [1‾11] orientation, whereas formation mechanisms and development processes of cell structures in [001] and [011] copper single crystals remain unclear. Therefore, this study examines the dislocation structures of near-[001] and near-[011] copper single crystals under cyclic deformation at high strain amplitudes. The cyclic stress–strain curve of the [011] crystals showed a distinct plateau at plastic shear strain amplitudes ≤7.5 × 10−3. In the plateau region, the dislocation structures consisted of cell structures along the (111) primary slip plane and matrix wall structures. Furthermore, (111) cell structures were formed in the single-slip deformation bands (DBs). After the plateau region, several types of new DBs could be observed due to the activation of multiple-slip systems. Multiple-slip DBs have a higher degree of plastic strain concentration than single-slip DBs, leading to the preferential formation of cell structures. For the near-[001] crystals, (111) cell structures were uniformly formed throughout the matrix, without the formation of DBs. The formation mechanism of the (111) cell boundary was independent of the stress axis and resulted from the interaction between the primary and coplanar slip systems.

Air infiltration characteristics in oxygen-enhanced and heated chambers on the Qinghai-Xizang Plateau

The Qinghai-Xizang Plateau is characterized by a low-pressure and oxygen-deficient environment due to its high altitude, causing discomfort and major safety problems for the inhabitants. To address this, oxygen-enriched chambers can be used to alleviate the plateau reaction. However, little consideration has been given to air infiltration in these chambers, with a lack of information on the corresponding infiltration heat loss phenomenon. This paper addresses this by investigating the phenomenon of air flow in an oxygen-enriched chamber using experiments and simulations. The results highlight that when there is a difference in oxygen concentration between the interior and exterior of the chamber, mass transfer occurs due to both the molecular diffusion in addition to a flow due to the air density difference caused by the variation in concentration. Also, the simultaneous stack effect is roughly equivalent to 10 times the oxygen pressure, and the two pressure effects act in opposite directions. It is also noted that both the oxygen pressure and the stack effect decrease as the atmospheric pressure decreases. Overall, the oxygen-enriched chambers exhibit less infiltration in plateau areas with a low atmospheric pressure compared to plains areas with a relatively high atmospheric pressure. Finally, this study establishes formulas that can be used to calculate air infiltration rates in oxygen-enriched chambers. This study fills a gap in the existing literature regarding the air infiltration mechanism in oxygen-enriched chambers at high altitudes and low pressures, providing a theoretical foundation for improving indoor environments in the Qinghai-Xizang Plateau and other high-altitude regions.

Real-time measurement of two-dimensional LET distributions of proton beams using scintillators.


The linear energy transfer (LET) of proton therapy beams increases rapidly from the Bragg peak to the end of the beam. Although the LET can be determined using analytical or computational methods, a technique for efficiently measuring its spatial distribution has not yet been established. Thus, the purpose of this study is to develop a technique to measure the two-dimensional LET distribution in proton therapy in real time using a combination of multiple scintillators with different quenching. Inorganic and organic scintillator sheets were layered and irradiated with proton beams. Two-color signals of the CMOS sensor were obtained from the scintillation light and calibration curves were generated using LET. LET was calculated using Monte Carlo simulations as LETt and LETd weighted by fluence and dose, respectively. The accuracy of the calibration curve was evaluated by comparing the calculated and measured LET values for the 200 MeV monoenergetic and spread-out Bragg peak (SOBP) beams. LET distributions were obtained from the calibration curves.
Main results:
The deviation between the calculated and measured LET values was evaluated. For both LETt and LETd, the deviation in the plateau region of the monoenergetic and SOBP beams tended to be larger than those in the peak region. The deviation was smaller for LETd. In the obtained LETd distribution, the deviation between the calculated and measured values agreed within 3% in the peak region, while the deviation was larger in other regions. The LET distribution can be measured with a single irradiation using two scintillator sheets. This method may be effective for verifying LET in daily clinical practice and for quality control.&#xD.

The structural and mechanical properties of open-cell aluminum foams: Dependency on porosity, pore size, and ceramic particle addition

Aluminum foams are desired for lightweight, high-performance, and cost-effective materials, particularly in automotive, aerospace, and advanced power plants. Expansion of their applications depends on developing a detailed understanding of the structural and mechanical properties of aluminum foams. In this research, open-cell aluminum foams with 25.51–81.88 % porosity were manufactured through powder metallurgy using a space holder technique, with varying carbamide (urea) ratios (17–80 %) and particle sizes (1–1.4 mm, 1.7–2 mm, 2–2.4 mm). Three different ceramic particles, B4C, Al2O3, and SiC were used as reinforcement to improve the compression properties and energy absorption capacity of the foam materials. The study determined open and closed porosity ratios, spherical diameter, sphericity values, micropore sizes, mechanical properties, and energy absorption capacity of the foam samples both with and without ceramic additives. The results show that porosity ratio, pore size, and ceramic particle addition significantly affect aluminum foams' structural and mechanical properties, allowing for tailored properties for specific applications. It was observed that as porosity increased, compressive stress decreased, and the length of the plateau region and the shape change where densification began increased. However, there was no significant change in compressive stress and specific energy values with changing pore size. The optimal B4C addition was found to be 4 %, which significantly improved compressive strength to 3.75 MPa and specific energy to 4.24 MJ m−3.

Evaluation and projection of changes in temperature and precipitation over Northwest China based on CMIP6 models

AbstractNorthwest China is much more sensitive to climate warming, and the climate has varied rapidly from warm and drought to warm and humid conditions. In addition, due to the complex terrain of Northwest China, the methods and parameterization schemes of different CMIP6 models, these models are mostly applied to arid areas in Northwest China or Central Asia, lacking climate data for plateau areas and eastern Lanzhou, specifically in filtering CMIP6 models and evaluating applicable models. In this paper, 34 CMIP6 climate models are used to evaluate and forecast future trends in Northwest China under the SSP126, SSP245 and SSP585 scenarios in the short, medium and long term. CMIP6 models of temperature and precipitation are identified by applying the interannual variability skill score (IVS) between CN05.1 datasets and historical CMIP6 models, which are suitable for Northwest China. Then, we assess the characteristics, warming and wetting deviations, and uncertainties in the prediction of climatic change according to CMIP6 models over Northwest China. The results show that CMIP6 models in precipitation and temperature applicable to Northwest China are AWI‐CM‐1‐1‐MR, BCC‐CSM2‐MR, FGOALS‐g3, INM‐CM4‐8, INM‐CM5‐0 and MRI‐ESM2‐0. The multi‐model ensemble mean (MMEM) has better capability than individual CMIP6 models in precipitation and temperature prediction. Spatiotemporal climatic change over Northwest China shows overall warming and wetting trends. The IVS provides the ability to estimate CMIP6 model simulation performance both temporally and spatially. The temperature simulation is quite good in the Tarim Basin and Hexi Corridor region, and the precipitation simulation is quite good in the plateau region, Altai Mountains, Tianshan Mountains and Hexi Corridor region. Cold and wet deviations occur in Northwest China due to the topography and few stations, which are common reasons. The main sources of uncertainties in temperature prediction during this century are model uncertainty (before the 2090s) and scenario variability (after the 2090s), and model uncertainty in precipitation for CMIP6 becomes the main source of uncertainty.

Satellite Based Composite Weather Insurance Product for assessing mid-term adversary

The present study formulated a satellite-based rainfall insurance product (SRIP) at sub-seasonal scale during 2015–2020 by integrating meteorological, geophysical and vegetation index products e.g. rainfall (CHIRPS:Climate Hazards Group InfraRed Precipitation with Station), soil moisture (SMAP), normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) from moderate resolution imaging spectro-radiometer (MODIS). The SRIP was meticulously designed to integrate both cause (rainfall) and impact (NDVI, NDWI, soil moisture) parameters to enhance the assessment of min-season crop risks, with a particular emphasis on deficit rainfall. The performance evaluation of SRIP was conducted in two distinct agro-climatic zones viz. Deoria district of Uttar Pradesh (Upper Gangetic Plain Region) and Krishna district of Andhra Pradesh (Southern Plateau and Hills Region) spanned from June to October, which aligns with the major crop-growing season corresponding to the Southwest monsoon period in India. Three sets of SRIPs were investigated i.e. SRIP with cause parameter (SRIP1), SRIP with cause-impact parameters with no lag response (SRIP2) and SRIP with cause-impact parameters with one-month lag response (SRIP3). The SRIP was structured to provide a numerical index on a scale ranging from 0 to 1, representing poor to good crop-growing conditions that could effectively identify the rainfall deficit threshold (SRIP≤0.43) corresponding to negative percent deviation in rainfall (PDR≤−20%). This threshold level was recognized for compensation of triggers at the multiple crop growth phases during the crop-growing season. The district average of SRIP and PDR showed fair correlation co-efficient (0.77 ≤ r ≤ 0.88). Good correlation between sub-seasonal (monthly, bi-monthly, tri-monthly) SRIP and normalized MODIS Gross Primary Productivity (0.65 ≤ r ≤ 0.98), and SRIP deviation and yield deviation (0.45 ≤ r ≤ 0.97) reflect sensitivity of SRIP to crop carbon productivity and crop yield. The findings of the present study recommend SRIP not only a multi-phase composite index for assessing mid-season crop risks in terms of rainfall deficit for clusters of insurance units, but it has the potential to be used by insurance agencies to settle the claims by farmers in a transparent and faster manner for crop loss due to large-scale rainfall deficits. However, SRIP needs to be customized in future to make it more adaptable to settle insurance claims due to weather adversaries at individual farm level.

Remote Sensing Mapping and Analysis of Spatiotemporal Patterns of Land Use and Cover Change in the Helong Region of the Loess Plateau Region (1986–2020)

Land use and cover change (LUCC) is directly linked to the sustainability of ecosystems and the long-term well-being of human society. The Helong Region in the Loess Plateau has become one of the areas most severely affected by soil and water erosion in China due to its unique geographical location and ecological environment. The long-term construction of terraces and orchards is one of the important measures for this region to combat soil erosion. Despite the important role that terraces and orchards play in this region, current studies on their extraction and understanding remain limited. For this reason, this study designed a land use classification system, including terraces and orchards, to reveal the patterns of LUCC and the effectiveness of ecological restoration projects in the area. Based on this system, this study utilized the Random Forest classification algorithm to create an annual land use and cover (LUC) dataset for the Helong Region that covers eight periods from 1986 to 2020, with a spatial resolution of 30 m. The validation results showed that the maps achieved an average overall accuracy of 87.54% and an average Kappa coefficient of 76.94%. This demonstrates the feasibility of the proposed design and land coverage mapping method in the study area. This study found that, from 1986 to 2020, there was a continuous increase in forest and grassland areas, a significant reduction in cropland and bare land areas, and a notable rise in impervious surface areas. We emphasized that the continuous growth of terraces and orchards was an important LUCC trend in the region. This growth was primarily attributed to the conversion of grasslands, croplands, and forests. This transformation not only reduced soil erosion but also enhanced economic efficiency. The products and insights provided in this study help us better understand the complexities of ecological recovery and land management.

Harnessing spectrophotometry resolution power for determining ternary mixture for respiratory disorders treatment in their pharmaceutical formulation.

A ternary mixture incorporating Hydroxyzine hydrochloride (HYX), Ephedrine hydrochloride (EPH) and Theophylline (THP) frequently prescribed for the treatment of respiratory diseases. Herein, two spectrophotometric methods are designated and applied to resolve these three components in their mixture. Method A is ratio-subtraction combined with derivative spectrophotometry, where THP can be determined directly at its λmax 271 nm (neither HYX or EPH interfere), then for determination of HYX and EPH, the ternary mixture was divided by 22 μg/mL of THP and after subtraction of the plateau region, HYX can be determined directly at its λmax 234.2 nm (absence of EPH intervention). Finally, the third derivative (3D) spectrophotometric approach was utilized to estimate EPH by detecting the peak amplitude at 222 nm with Δλ = 4 and a scaling factor 100. Principal Component Regression (PCR) and Partial Least Squares (PLS), two multivariate calibration approaches, were applied effectively in Method B. This method effectively quantified the mixture under investigation by using the absorption spectra obtained from suitable solutions of the three components in the 210-230 nm region. The calibration models were evaluated using cross-validation with PCR and PLS, producing statistical characteristics that demonstrate the effectiveness of the calibration models. Synthetic and pharmaceutical preparations were also used to conduct external validation. In pharmaceutical formulation, these methods were successfully applied to analyze HYX, EPH, and THP without overlap from formulation's excipients. Moreover, the study's findings were statistically contrasted with those of earlier reported HPLC method. Appraisal approaches were used to determine whether the new spectrophotometric methods had an adverse environmental impact involving the Green Analytical Procedure Index (GAPI) and the AGREE (Analytical Greenness). These evaluations delivered information about the methods' eco-friendliness and sustainability, proving that they are in line with ecologically attributed practices. Furthermore, the Blue Applicability Grade Index (BAGI) was utilized to identify and verify the feasibility and practicality of the suggested approaches.

Temperature-dependent dielectric measurements of polypyrrole/zinc cobalt oxide nanocomposites by impedance spectroscopy

This study characterizes the conduction mechanism in Zinc Cobalt oxide/Polypyrrole nanocomposites (ZCO/PPy NCs) concerning temperature (303–453 K) and frequency (100 Hz–1 MHz). To obtain the ZCO/PPy nanocomposites for the experiments, we used the in-situ chemical polymerization technique to disseminate varying weight percentages of ZCO nanoparticles (ZCO NPs) in the PPy matrix. The total electrical conductivity graph consists of a step-like feature of a plateau and dispersive regimes. The dispersive zone, which follows Jonscher's power law, correlates to AC conductivity, whereas the plateau region, which corresponds to DC conductivity, is thermally activated. The extracted DC conductivity values are of the order of 10‐4 S/m at 303 K. The conduction mechanism in ZCO/PPy nanocomposites is depicted by the Non-Overlapping Large Polaron Tunneling (NSPT) model. The dielectric studies confirm the non-Debye-like relaxation in PPy and ZCO/PPy NCs. In addition, the complex impedance and equivalent circuit analysis showed maximum contribution from grain and grain boundaries. The grain and grain boundary resistances are of the order of 103 Ω, depicting the electrical homogeneity in the PPy and ZCO/PPy nanocomposites.

Predicting plateau atmospheric ozone concentrations by a machine learning approach: A case study of a typical city on the southwestern plateau of China

Atmospheric ozone (O3) has been placed on the priority control pollutant list in China's 14th Five-Year Plan. Due to their unique meteorological conditions, plateau regions contain high concentrations of atmospheric O3. However, traditional experimental methods for determining O3 concentrations using automatic monitoring stations cannot predict O3 trends. In this study, two machine learning models (a nonlinear auto-regressive model with external inputs (NARX) and a temporal convolution network (TCN)) were developed to predict O3 concentrations in a plateau area in the Kunming region by considering the effects of meteorological parameters, air quality parameters, and volatile organic compounds (VOCs). The plateau O3 prediction accuracy of the machine learning models was found to be much higher than those of numerical models that served as a comparison. The O3 values predicted by the machine learning models closely matched the actual monitoring data. The temporal distribution of plateau O3 displayed a high all-day peak from February to May. A correlation analysis between O3 concentrations and feature parameters demonstrated that humidity is the feature with the highest absolute correlation (−0.72), and was negatively correlated with O3 concentrations during all test periods. VOCs and temperatures were also found to have high positive correlation coefficients with O3 during periods of significant O3 pollution. After negating the effects of meteorological parameters, the predicted O3 concentrations decreased significantly, whereas they increased in the absence of NOx. Although individual VOCs were found to greatly affect the O3 concentration, the total VOC (TVOC) concentration had a relatively small effect. The proposed machine learning model was demonstrated to predict plateau O3 concentrations and distinguish how different features affect O3 variations.

Environmental changes and human impacts over the past 1200 years: Evidence from high-resolution pollen records from peat in the Yunnan-Guizhou Plateau, Southwest China

Over the past millennium, the understanding of vegetation and climate changes in mountainous regions, driven by both natural and anthropogenic forces, remains unclear. In this study, we provide a high-resolution vegetation record spanning the past 1200 years from a subalpine peatland in the Niangniang Mountains, southwestern China. By analyzing pollen, charcoal, and loss-on-ignition from the peat sediment, we elucidate the interactions between vegetation, fire, and human impact. Our findings reveal that before 1150 CE, the mountains were covered with dense broadleaf forests and experienced minimal human activity. Natural forcings, primarily climatic conditions, drove vegetation succession and forest fires. After 1150 CE, the Human Influence Index (HII) increased sharply, coinciding with a rise in cereal-type pollen. Significant agricultural activities in the southwestern mountainous regions of China began after 1150 CE, which is later than those in the low-altitude lake basins of southwestern China. During the Medieval Climate Anomaly (MCA, 836–1400 CE), the Niangniang Mountains were characterized by warm and humid climatic conditions, a stable forested landscape, and a high peat carbon accumulation rate. Although human activities increased markedly during this period, the arbors did not undergo notable changes, and climate forcings continued to have a greater impact on vegetation than anthropogenic forcings. During the Little Ice Age (LIA, 1400–1900 CE), the regional vegetation landscape transitioned from dense forests to open grasslands as climate conditions became cold and dry, reducing peat carbon accumulation rate. This period also saw increased forest fires and significant human-driven deforestation, with anthropogenic forcings becoming dominant. After 1900 CE, vegetation changes were increasingly influenced by government policies. Comparison with major climate forcings and spectrum analysis have shown that variations in monsoon intensity, regulated by solar and volcanic activity, have influenced the climate and peat depositional environment in the Niangniang Mountains. Our research offers meaningful insights into forest conservation in the mountainous regions of the Yunnan-Guizhou Plateau.

The influence of resonant light pulses on high harmonic generation in solids

Abstract We have theoretically studied the high harmonic generation (HHG) in solids driven simultaneously by a mid-infrared (MIR) laser and a high-order harmonic pulse with energy around the band gap between the valence band and conduction band. By adding this resonant harmonic light pulse with the relative intensity ratio of 4\%, the high-order harmonic emission from the crystal is enhanced by 1-2 orders of magnitude. The yield of HHG in solid increases monotonically with the relative strength of the resonant harmonic pulses. In addition, we also found that HHG dynamics from the $k$ channel around the boundary of the Brillouin zone can be selectively enhanced by adjusting the frequency of the resonant high-order harmonic pulse. The resonance-enhanced HHG and $k$ channel selection effect in solids is also investigated by using the three-band semi-conductor Bloch equation for HHG in ZnO. We also find that the harmonic in the plateau region driven by adding a resonant light field to the strong MIR driving field has less red-shifted compared with the case driven by the MIR driving field alone.

Dynamics of the Interaction between Freeze–Thaw Process and Surface Energy Budget on the Permafrost Region of the Qinghai-Tibet Plateau

Dynamics of the Interaction between Freeze–Thaw Process and Surface Energy Budget on the Permafrost Region of the Qinghai-Tibet Plateau

Impacts of elevated anthropogenic emissions on physicochemical characteristics of black-carbon-containing particles over the Tibetan Plateau

Abstract. Black carbon (BC) in the Tibetan Plateau (TP) region has distinct climate effects that strongly depend on its mixing state. The aging processes of BC in the TP are subject to emissions from various regions, resulting in considerable variability of its mixing state and physicochemical properties. However, the mechanism and magnitude of this effect are not yet clear. In this study, field observations on physicochemical properties of BC-containing particles (PMBC) were conducted in the northeast (Xihai) and southeast (Lulang) regions of the TP to investigate the impacts of transported emissions from lower-altitude areas on BC characteristics in the TP. Large spatial discrepancies were found in the chemical composition of PMBC. Both sites showed higher concentrations of PMBC when they were affected by transported air masses outside the TP but with diverse chemical composition. Source apportionment for organic aerosol (OA) suggested that primary OA in the northeastern TP was attributed to hydrocarbon OA (HOA) from anthropogenic emissions, while it was dominated by biomass burning OA (BBOA) in the southeastern TP. Regarding secondary aerosol, a marked enhancement in nitrate fraction was observed on aged BC coating in Xihai when the air masses were brought by updrafts and easterly winds from lower-altitude areas. With the development of boundary layer, the enhanced turbulent mixing promoted the elevation of anthropogenic pollutants. In contrast to Xihai, the thickly coated BC in Lulang was mainly caused by elevation and transportation of biomass burning plumes from south Asia, showing a large contribution of secondary organic aerosol (SOA). The distinct transported emissions lead to substantial variations of both chemical composition and light absorption ability of BC across the TP. The thicker coating and higher mass absorption cross-section (MAC) of PMBC in air masses elevated from lower-altitude regions reveal the promoted BC aging processes and their impacts on the mixing state and light absorption of BC in the TP. These findings emphasize the vulnerability of plateau regions to influences of elevated emissions, leading to significant changes in BC concentration, mixing states and light absorption across the TP, all of which need to be considered in the evaluation of BC radiative effects for the TP region.

A critical assessment of the onset strain of densification in the evaluation of energy absorption for additively manufactured cellular materials

Densification strain is an essential parameter in the characterization of energy absorption of additively manufactured cellular structures. In addition to its own merits as a metric that indicates usable stroke length for energy absorbers, it is central to the computation of energy absorbed by the structure. However, at least four different approaches have been used in the literature, each with its own limitations. In this work, a critical review of these approaches is first presented. While the maximum efficiency approach has been demonstrated to be optimal for cellular foams, this work shows how, for some additively manufactured cellular materials, it can fail to estimate densification strain accurately due to its sensitivity to instantaneous stress values in the plateau region. An alternative method is proposed in this work that leverages peak stress instead to determine the onset strain of densification and is shown to be consistently accurate across a range of cellular materials. The method is validated with the results from an experimental study of energy absorption in six different types of cellular structures across three relative densities, with identical geometries fabricated in two different base materials and processes: AlSi10Mg with Laser Powder Bed Fusion, and Nylon-12 with Selective Laser Sintering.