The statistics of the Conference International des Grands Reseaux Electriques (CIGRE) indicate that the operational reliability of SF6 gas‐insulated equipment (GIE) is very high; however, the failure ...rate of the GIE in operation is much higher than that of the IEC standard, and the fault occurs frequently in the GIE at a high voltage level. The reason is due to the complex and strong on‐site electromagnetic interference environment and fully enclosed structure of GIE. The key method and technology for effective on‐line monitoring and fault diagnosis of GIE are still lacking. Given the partial strong electromagnetic energy and high temperature induced by early latent insulation faults in the equipment, SF6 gas insulation presents different degrees of decomposition. The decomposition products mainly include SO2F2, SOF2, SO2, HF, and H2S. The decomposition characteristics of SF6 are closely related to the property of insulation faults. At present, this area is attracting attention from the power industry and research institutes. This study summarises the current research on SF6 decomposition component analysis (DCA). The content mainly includes the latest progress of SF6 decomposition characteristics and mechanism under fault conditions, and fault diagnosis methods based on decomposition components.
The field of self-adaptive software is becoming increasingly crucial because software has to adapt its behavior at runtime to keep up with dynamic and constantly evolving environments. The ability of ...software to modify and adjust itself is known as adaptability, which has been acknowledged as an important quality attribute. As software architecture development represents the initial stage of the design process, architectural design has emerged as a critical development activity. The degree to which the architecture can adapt to changes will be the key factor in determining the adaptability of the software ultimately released to users. Existing metrics for software architectural adaptability typically view adaptability as a positive attribute, meaning that any possibility of change in architectural elements is perceived as an improvement in adaptability. However, the application of adaptability that leads to increased costs or complexity can only be seen as a negative attribute. In other words, the side effects brought about solely for the purpose of achieving adaptability are greatly overlooked; that is, the impacts caused by adaptability exhibit both symmetry and asymmetry for software architectural adaptability. On the other hand, the existing measures of adaptability only define it from the perspective of whether a module will change, without considering changes beyond the topological structure under multiple strategies. In this paper, we propose a comprehensive assessment approach to measure software architecture adaptability. Multiple factors are considered, including the number and types of strategies employed, the cost of completing the adaptation, the extent of changes made to the architectural elements, and the overall impact of the adaptation on the architecture. An extended UML (e-UML) component diagram is presented to model software architectural changes under various types of strategies. Finally, an experiment on the znn.com software is conducted to validate the practical feasibility of our proposed method. Our approach can assist software architects in making informed decisions regarding software architecture design options to improve the adaptability and longevity of their software systems.
Context
SF
6
gas has a strong greenhouse effect, and how to treat SF
6
in an environmentally friendly way has been a hot topic of current research. In this paper, the adsorption behavior of SF
6
on ...the surface of Pd-doped hydroxyl-terminated modified Ti
3
C
2
T
x
(i.e., Ti
3
C
2
(OH)
2
) was investigated based on the density functional theory using two-dimensional MXene as the catalyst. The structures of different Pd-doped Ti
3
C
2
(OH)
2
were analyzed and the most structurally stable doped structures were selected as the basis for subsequent calculations. A large number of adsorption configurations were constructed and geometrically optimized, and the adsorption energy, charge transfer, differential charge density, and density of states of the systems were calculated in order to analyze the gas–solid interactions and find the surface active sites; compared with the adsorption performance of undoped Ti
3
C
2
(OH)
2
on SF
6
, it was found that Pd doping played a less inhibitory role in the adsorption of SF
6
on the Ti
3
C
2
(OH)
2
surface. The results of this study can provide theoretical support for the use of Pd-doped Ti
3
C
2
(OH)
2
as a catalyst for the degradation of SF
6
.
Methods
In this paper, simulations of SF
6
adsorption on Ti
3
C
2
T
x
surfaces are based on density functional theory and are carried out in the Dmol
3
module of Material Studio. To better describe the non-uniform electron density of the actual system, the PBE functional in the generalized gradient approximation (GGA) was chosen for the optimization of the structure of the gas–solid interface system and the calculation of the relevant electronic properties, combined with the Grimme dispersion correction in the DFT-D dispersion correction for the electron exchange correlation term. Because both Pd and Ti are transition metal elements, the mode-conserving pseudopotential DNP basis set containing relativistic effects was chosen for the electronic wave function expansion. In this paper, an all-electron model is used for the inner core treatment of gas molecules and a density generalized semi-nuclear pseudopotential DSSP is used for the solid surface treatment.
To investigate the decomposition law of SF6 under negative direct current partial discharge (PD) at different energies, a SF6 PD hybrid numerical model based on fluid dynamics and plasma chemical ...reaction models, in which 14 particle species and 24 chemical reactions are considered, is proposed. The effectiveness of the proposed model is validated with the current pulse waveform and the V–I discharge curve obtained by experiment. The influence of discharge energy on SF6 PD characteristic quantities and SF6 decomposition products is investigated with simulation and experiment. The results show that most of the discharge area of SF6 is neutral, and the cation clouds only exist in the ionosphere (4.79–5 mm). With the increase in applied voltage, the electric field intensity of the needle plate gap does not increase completely and even decreases in some areas. Moreover, different from the traditional opinion, the generation of SO2F2 under PD is mainly generated by the hydrolysis reaction of SOF4, which is formed by SF5, SF4, and OH, O. The reaction path of SF2 with O2 is not important. Thus, c(SO2F2)/c(SOF2 + SO2) can be used as the energy characteristic component ratio because of its ability to represent the low-fluorine sulfide ratio n(SF5)/n(SF4).
Abstract Triboelectric nanogenerator (TENG) operates on the principle of utilizing contact electrification and electrostatic induction. However, visualization and standardized quantification of ...surface charges for triboelectric materials remain challenging. Here, we report a surface charge visualization and standardized quantification method using electrostatic surface potential measured by Kevin probe and the iterative regularization strategy. Moreover, a tuning strategy on surface charge is demonstrated based on the corona discharge with a three-electrode design. The long-term stability and dissipation mechanisms of the injected negative or positive charges demonstrate high dependence on deep carrier traps in triboelectric materials. Typically, we achieved a 70-fold enhancement on the output voltage (~135.7 V) for the identical polytetrafluoroethylene (PTFE) based TENG (neg-PTFE/PTFE or posi-PTFE/PTFE triboelectric pair) with stable surface charge density (5% decay after 140 days). The charged PTFE was demonstrated as a robot e-skins for non-contact perception of object geometrics. This work provides valuable tools for surface charge visualization and quantification, giving a new strategy for a deeper understanding of contact electrification.
Soil bacteria participate in nutrient cycling above and below ground to promote ecosystem stability and health. However, the relationship of soil bacteria and environmental factors following the ...Grain for Green (GfG) program remains poorly understood in southwest China. Soil samples were collected from seven Grain for Green sites that had been revegetated for 15 years. Four of these sites were afforested with a different tree species:
Zenia insignis
(ZI),
Toona sinensis
(TS),
Castanea mollissima
(CM), and
Citrus reticulate
(CR). One site was revegetated with
Zenia insignis
and Guimu-1 elephant grass (ZG), and one with only Guimu-1 elephant grass (GM). The remaining site, abandoned cropland (AC), was left to regenerate naturally. Here, we used Illumina sequencing of 16S rRNA genes to explore how the Grain for Green project affected soil bacterial community. We found that Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria were the dominant phyla in these soils. The dominant genera at each revegetation site were also different. The CM, ZI, TS, and AC sites were dominated by Micromonospora, ZG was dominated by Streptomyces, and CR and GM were dominated by Subgroup 6. The bacterial structure was most similar in AC and TS. Correlation analysis showed that the ratio of C:P had positive effects on KD4-96, Intrasporangiaceae, and
Gaiella
. The ratio of soil N:P was significantly positively correlated with
Cupriavidus
and
Kribbella
. The combination of planting
Zenia insignis
and Guimu-1 elephant grass had the best edaphic benefits, and the approach of planting
Citrus reticulate
and
Toona sinensis
needs to be improved. Redundancy analysis (RDA) revealed that plant Simpson index, and soil N:P contributed to 16 and 15.7% of the total variations in the soil bacterial community composition, respectively. Our results suggested that plant diversity (Simpson index) and soil stoichiometric ratio (N:P) were the important factors affecting the bacterial community, and phosphorus was the limiting factor of the bacterial community in the Grain for Green karst region. In the future, revegetation should be accompanied with phosphorus fertilizer and polycultures should be considered.
Four review papers summarise the latest research progress from the perspectives of intelligent perception of large-scale interconnected grid situation, intelligent perception of distribution network, ...intelligent perception of high-voltage and high-power electronic equipment and gas-insulated equipment condition, especially the deep application of artificial intelligence and new sensing technology in these fields. Intelligent perception of the grid situation, as an inevitable trend of development of power grid and Energy Internet in the future, is believed to receive more extensive attention and continuous investment. ...we would like to express our sincere thanks to Dr. Zheng Xiao, Ms. Yangyang Yu and Ms. Muchen Ran from ‘High Voltage’ editorial department for their full support in the planning, manuscript invitation, review and editing of this topic.
Currently, China is using the SF6/N2 gas mixture to gradually replace SF6 in GIS and other equipment. However, gas-insulated equipment will inevitably have local overheating faults. The SF6/N2 gas ...mixture will decompose to some extent at high temperatures. Impurities such as moisture in the equipment can affect this decomposition process. At present, there are fewer studies on the moisture content of the superheated decomposition of the SF6/N2 gas mixture. Therefore, this paper carries out the SF6/N2 mixed gas superheat decomposition experiment on the constructed superheat decomposition simulation experiment platform. By changing the content of trace water, the influence of trace water on the decomposition of the SF6/N2 mixed gas insulation medium with superheat failure was initially investigated. It is found that trace H2O will promote the generation of SF6 characteristic decomposition products, especially for the generation of SO2F2. The generation of SO2 in the product is the largest, and its generation process needs the full participation of H2O. In addition, the addition of trace water will also improve the yield of nitrogen-containing products NO and NO2, and under the experimental conditions of this paper, by adding the microwater, the yield reaches 100–300 µl/l. The reaction mechanism of H2O decomposition and combining with N atoms to generate NO and NO2 at high temperatures was analyzed in this paper. The thermodynamic properties of the main reaction paths and the equilibrium constants were calculated based on the density functional theory, which provided theoretical references for the further study of the mechanism of SF6/N2 superheated decomposition.
In karst ecosystems, plants absorbing smaller amounts of nutrients, owing to shallow soil, show limited growth. In addition, fine roots (diameter < 2 mm) contribute to the regulation of nutrient ...cycles in terrestrial ecosystems. However, the spatial and temporal variations of fine root biomass in different vegetation types of the karst region remains poorly understood. In this study, we investigated the seasonal and vertical variation in biomass, necromass, and total mass of fine roots using sequential soil coring under different stages of vegetation restoration (grassland, shrubland, secondary forest, and primary forest) in Southwest China. The results showed that the fine root biomass and necromass ranged from 136.99 to 216.18 g m
and 47.34 to 86.94 g m
, respectively. The total mass of fine roots and their production ranged from 187.00 to 303.11 g m
and 55.74 to 100.84 g m
year
, respectively. They showed a single peak across the vegetation restoration gradient. The fine root biomass and total fine root mass also showed a single peak with seasonal change. In autumn, the fine root biomass was high, whereas the necromass was low. Most of the fine roots were concentrated in the surface soil layer (0-10 cm), which accounted more than 57% root biomass, and decreased with increasing soil depth. In addition, fine root production showed a similar vertical pattern of variation with biomass. Overall, our results suggested that fine roots show clear seasonal and vertical changes with vegetation succession. Moreover, there was a higher seasonal fluctuation and a greater vertical decreasing trend in late-successional stages than in the early-successional stages. The conversion of degraded land to forest could improve the productivity of underground ecosystems and vegetation restoration projects in the fragile karst region should, therefore, continue.
Bacteria play an important role as decomposers in karst ecosystems, which can be associated with karst soil and plants, promoting the cycling of nutrients between plants and soil. To reveal the ...diversity and structure of soil bacterial communities in some karst land-use types after the Grain for Green pattern, soil samples were collected from different land-use types (crops, grasses, and plantations) for analysis. Changes in the structure and assembly of karst soil bacteria were examined using 16S rRNA Illumina sequencing and soil chemical properties. We found that 18 years after the Grain for Green program, the soil chemical properties of available nitrogen (AN), total phosphorus (TP), total nitrogen (TN), and soil organic matter (SOM) of grassland were significantly different from those of farmland. The soil chemical properties in plantations were also significantly lower than those in farmlands. Different land-use types did not significantly affect the soil bacterial community structure. Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria were the dominant phyla in all the plots. The relative abundance of Proteobacteria was higher in grasslands and plantations than in farmlands, whereas that of Actinobacteria was lower in grasslands. Furthermore, no significant correlations were observed between the soil chemical factors and soil bacterial groups at the genus level. The null model analysis indicated that dispersal limitations in stochastic processes predominated for the different land-use systems. Combined with previous analyses of the factors driving bacterial core species diversity in karst soils, we speculated that stochastic processes play a more important role in the construction of core bacterial species in restored karst soils at the plot scale.
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