Spatio-Temporal Characteristics and Driving Mechanism of Alpine Peatland InSAR Surface Deformation—A Case Study of Maduo County, China

Surface deformation of alpine peatland in China has an important effect on runoff and is of great significance for wetland ecosystem protection. However, spatio-temporal characteristics of alpine peatland surface deformation in China lack systematic studies, and the driving mechanism is not yet clear. In this study, we selected the alpine peatland of Maduo County in China as the research object, surface deformation of peatland based on the small baseline subset radar interferometry technique was obtained, we analyzed spatio-temporal deformation characteristics and patterns of peatland, explored the driving mechanism of the peatland surface deformation with single-factor and multifactor combinations of Geo-detector, respectively. The results showed that the overall subsidence rates of peatlands in Maduo County, China slowed down year by year from 2018 to 2020, but there was seasonal freezing and thawing, subsidence rates of peatlands at high elevation and high slopes were stable, peatlands at low elevation and low slope were vulnerable to disturbance, subsidence rates are largest. Maliecuo, Bailongqu, and Gaerlawangzang regions were serious subsidence, the maximum subsidence rate was 159 mm/year. Meteorological factors and geological conditions were the main reasons for the surface deformation of alpine peatland in Maduo County, China. This study provides a theoretical basis for the conservation and restoration of peatland ecosystems in the alpine regions of China

Difference analysis of dissolved gas in natural ester insulating fluids under typical electrical and thermal faults: An experimental study

Abstract Natural ester insulating oil is widely used in transformers due to its good fire resistance and biodegradability. It is mainly composed of triglycerides, and there are some differences in fatty acid composition and content among natural esters. Therefore, the fault diagnosis methods based on dissolved gas analysis are different. Three kinds of natural ester insulating oils are used to study the dissolved gas in oil under typical electrical and thermal faults of power transformers. Thermal faults from 200°C to 800°C and electrical faults with different discharge energies, which include partial discharge, breakdown discharge, and arc discharge, are simulated. The characteristic gases and their variation trends of natural esters under thermal and electrical faults are obtained through the experimental results. The gas generation characteristics of the three natural ester insulating oils under typical electrical and thermal faults are almost similar, but the relative percentages of characteristic gases have certain differences. Natural ester insulating oil with a higher unsaturation degree tends to produce more H2 and less C2H4. Finally, the fault diagnosis methods are used to determine the fault gas data, and the Duval pentagon is modified and improved according to the gas generation characteristics of natural esters

Magneto-electronic properties and tetragonal deformation of rare-earth-element-based quaternary Heusler half-metals: A first-principles prediction

This manuscript reports the theoretical results on the magneto-electronic properties of 8 new rare-earth-element-based equiatomic quaternary Heusler (EQH) half-metallic materials (HMMs) MCoTiZ (M = Lu, La; Z = Si, Ge, Sn) and ScCoTiN (N = Si, Ge) by means of the first-principles calculations. It is observed that all the EQH compounds (type III structure) studied in this work are stable in the ferromagnetic phase. The total magnetic moments of these EQH HMMs are all 2 μ B and they obey the well-known Slater-Pauling behavior, M t = Z t -18, M t is the total magnetic moment and Z t is the total number of valence electrons. The half-metallic band gaps (E HM ) of LuCoTiSi, LuCoTiGe, LuCoTiSn, LaCoTiSi, LaCoTiGe, LaCoTiSn, ScCoTiSi, and ScCoTiGe EQH compounds are respectively equal to 0.29 eV, 0.24 eV, 0.08 eV, 0.15 eV, 0.15 eV, 0.19 eV, 0.19 eV, and 0.15 eV. Compared to EQH HMMs only composed of 3d/4d transition metal elements, the E HM values of rare-earth-element-based EQH HMMs (except for LuCoTiSn) are larger, which is beneficial to the half-metallic stability in practical applications. Importantly, our work demonstrates that these compounds preserve their half-metallic states when the cubic primitive cell is tetragonally deformed or when the unit cell volume changes under the influence of uniform strain. Two types of strain are also applied to examine the magnetic and electronic properties of these compounds

Finite Element Modeling of Porous Microstructures With Random Holes of Different-Shapes and -Sizes to Predict Their Effective Elastic Behavior

Porous materials are promising media for designing medical instruments, drug carriers, and bioimplants because of their excellent biocompatibility, ease of design, and large variation of elastic moduli. In this study, a computational strategy using the finite element method is developed to model the porous microstructures and to predict the relevant elastic moduli considering the actual characteristics of the micropores and their distributions. First, an element-based approach is presented to generate pores of different shapes and sizes according to the experimental observations. Then, a computational scheme to evaluate the effective moduli of macroscopically isotropic porous materials based on their micro-mechanics is introduced. Next, the accuracy of our approach is verified with the analytical solutions of the extreme bounds of the elastic isotropic moduli of a simplified model and with the experimental data available in the literature. Finally, the influence of the shape of pores and their distribution modes are assessed

Tribological Properties of Mo2N Films at Elevated Temperature

Mo2N films were synthesized using the reactive magnetron sputtering system in a mixture of argon and nitrogen, and the tribological properties were investigated at different testing temperatures against an Al2O3 counterpart. The relative intensity ratio (RIR) method was used to calculate the weight fraction of the tribo-film (MoO3) on the wear tracks of the films. The results showed that the average friction coefficient first increased from 0.30 at 25 °C to 0.53 at 200 °C, and then decreased to 0.29 at 550 °C, while the wear rate decreased from 2.1 × 10−6 mm3/Nmm at 25 °C to 5.3 × 10−7 mm3/Nmm at 200 °C and then increased to 3.1 × 10−5 mm3/Nmm at 550 °C. The weight fraction of tribo-film was mainly attributed to changes in the average friction coefficient and the wear rate. Besides this, the relative humidity also influenced the tribological properties at 25–200 °C

Spatiotemporal dynamics of vegetation net ecosystem productivity and its response to drought in Northwest China

Net ecosystem productivity (NEP) quantifies magnitude of the terrestrial vegetation carbon sinks. Drought is one of the most important stressors affecting vegetation NEP. At present, the spatiotemporal dynamics of vegetation NEP in drought-prone of Northwest China (NWC) lack discussion under different climatic zones and land cover types, and the response of vegetation NEP to drought remains unclear. Hence, we estimated the vegetation NEP in NWC using ground and remote sensing data and quantified the spatiotemporal differentiation of NEP under different climatic zones and land cover types. The drought fluorescence monitoring index (DFMI) was developed to examine the relationship between vegetation NEP and drought response based on the solar-induced chlorophyll fluorescence (SIF) data. Our results suggested that vegetation carbon sinks increased significantly at 7.09 g C m−2 yr−1 in NWC during 2000–2019, mainly in northern Shaanxi, eastern and southern Gansu, and southern Ningxia. NEP showed increasing trends under different climatic zones and land cover types, but there were differences in carbon sink capacity. The strongest carbon sink capacity was in humid regions and forests, while the weakest was in arid regions and grasslands. The vegetation carbon sinks showed a non-linear relationship with the drought degree reflecting multiple trend differences, especially in forests and grasslands. The response to drought was faster and more significant in semi-arid and semi-humid transition zones and extreme humid regions when vegetation carbon sinks decreased. DFMI was a good indicator to monitor drought conditions in NWC. NEP and DFMI were an 8–20-month periodic positive correlation and showed a high correlation with high–high and low–low clustering spatially. Drought significantly weakened vegetation carbon sinks in NWC. This study emphasizes the demand to rapidly identify climatic conditions that lead to decrease significantly in vegetation carbon sinks and to formulate adaptation strategies aimed at reducing drought risk under global warming