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In order to study the flame retardant performance of corrugated flame arrester core on the explosion characteristics of 9.5% hydrogen/methane/air premixed gas, a self-built experimental platform was used to study the explosive characteristics and propagation rules and the impact of varying thicknesses and different volumes of hydrogen. The results indicated that the corrugated flame arrester core on the explosion flame of premixed gas was observed with two scenarios, quenching and penetration. The flame is dominated by reverse vortex flow after quenching, reversing the axial direction of flame propagation. However, the flame penetration leads to more intense burning reactions as φ increases. And the increase in thickness changes the flame structure forms a spherical flame to a mushroom-shaped flame and finally form a turbulent flame. The velocity of flame decreased significantly when L = 60 mm with φ = 10% and 20% respectively. The quenching effect is more obvious in P2 with hydrogen added, and its better performance with increasing thickness, with 9.76% and 3.70% decrease when L = 40 mm with φ = 10% and 20%, respectively, and with 57.05% and 48.55% decrease when L = 60 mm with φ = 10% and 20%, respectively. [ABSTRACT FROM AUTHOR]

A large number of gas explosion accidents have shown that secondary explosions are more dangerous and destructive than the primary. Based on the self-designed sliding experiment platform, the influence of sliding device on the evolution behavior of fuel enriched and lean flame fronts be compared. The study shown that adjusting the initial sliding position of porous media to 40 cm and using an appropriate spring coefficient can effectively extinguish methane flame in both fuel enriched and fuel lean combustion states. This method can reduce the range of flame diffusion, burning time and intensity compared with using fixed porous media, and also the maximum explosion overpressure. When using a sliding device in methane lean combustion, it can achieve significant reductions in the duration of the reverse diffusion flame (up to 64.02%), the quenching time of the flame (up to 44.21%), and the explosion overpressure inside the tube (up to 24.2%). During rich methane combustion, using sliding device can result in a reduction of up to 62.26% in the duration of the reverse diffusion flame, up to 46.81% in the quenching time of the flame, and up to 44.12% in the explosion overpressure inside the tube. Additionally, the inhibitory effect of the sliding device and the increase in elastic coefficient follow a pattern of initially increasing and then decreasing. In general, the sliding device is more effective in suppressing methane flames and overpressure during both enriched and lean fuel combustion than fixed device. The results can provide valuable insights for the development of secondary explosion prevention technology, which is crucial for preventing and managing methane explosion accidents. [ABSTRACT FROM AUTHOR]

To ensure the safe utilization of hydrogen-enriched natural gas (HENG), it is essential to explore effective explosion suppressants to prevent and mitigate potential explosions. This study experimentally investigates the impact of ultrafine water mist containing K2CO3 additives on the explosion characteristics of methane/hydrogen/air premixed combustion. The influence of varying K2CO3 concentrations on pressure rise rates and flame propagation was analyzed across different hydrogen blending ratios. The results demonstrate that the addition of K2CO3 to ultrafine water mist significantly enhances its suppression effects. The peak overpressure decreased by 41.60%, 56.15%, 64.94%, and 72.98%, the flame speed decreased by 30.66%, 70.56%, 46.72%, and 65.65%, and the flame propagation time was prolonged by 25%, 20.83%, 22.92%, and 18.75%, respectively, for different hydrogen blending ratios, showing a similar trend. However, the suppression effectiveness diminishes under high hydrogen blending ratios and low K2CO3 concentrations. Further analysis using thermogravimetric infrared spectroscopy and chemical kinetics simulations revealed that the heat release rate and the generation rate of active free radicals significantly decrease after the addition of K2CO3 to the ultrafine water mist. The recombination cycle of KOH → K → KOH, formed by reactions (R211: K + OH + M = KOH + M) and (R259: H + KOH = K + H2O), continuously combines active free radicals (·O, ·OH) into stable product molecules, such as H2O. However, at low K2CO3 concentrations, reaction R211, which suppresses laminar combustion sensitivity and consumes a larger quantity of active free radicals, does not dominate, leading to a reduced suppression effect of K2CO3 ultrafine water mist. Several factors during the reaction process also adversely affect the performance of K2CO3-containing ultrafine water mist. These factors include the premature onset of laminar flame instability at low K2CO3 concentrations, the increased flame-front propagation speed due to the addition of hydrogen to methane, which shortens the residence time of K2CO3 in the reaction zone, and the turbulence caused by unvaporized droplets. [ABSTRACT FROM AUTHOR]

Energy is an important aspect concerning global economic development and environmental conservation. Economic growth has been accompanied by extensive use of fossil fuels, resulting in significant emissions of greenhouse gases and other pollutants. Therefore, researchers have turned their attention to low/zero carbon fuels. Among these, biofuels have attracted wide attention due to their relatively low cost, clean combustion products and renewability. This article reviews the combustion, performance and emission characteristics of internal combustion (IC) engines fueled with biofuels categorized into three generations by their raw material sources. According to most research findings, biofuels generally exhibit poorer combustion performance in IC engines compared to fossil fuels due to their high viscosity and low lower heating value. However, these biofuels, characterized by a high oxygen content, facilitate more complete combustion and reduce emissions of CO, UHC and smoke, albeit increasing NOx emission and fuel consumption. Both thermal efficiency and brake power also tend to decrease, but various optimization strategies such as advanced combustion modes or injection control methods can partially compensate for these drawbacks. In conclusion, biofuels should be a promising low-carbon fuel for IC engines in the future. [ABSTRACT FROM AUTHOR]

Conducting polymers can be dynamically switched between being optically metallic (negative real permittivity) and dielectric (positive real permittivity) by varying their redox state. This has enabled nanoantennas with plasmonic resonances that can be reversibly turned on/off, opening for applications in dynamic metaoptics, reflective displays, and smart windows. However, previous reports on conducting polymer plasmonics were limited to p-type polymers. Here, we show that a highly conducting n-type polymer, called poly(benzodifurandione) (PBFDO), can also provide optically metallic properties and be used to make dynamic optical nanoantennas. The doped version of the polymer becomes metallic at wavelengths above around 700 nm, leading to plasmonic extinction peaks for nanodisks made from the material. These peaks can be reversibly switched off and on electrically or chemically by varying the doping level of the polymer. The study extends the field of dynamic polymer plasmonics to n-type materials and broadens the application areas of PBFDO. [ABSTRACT FROM AUTHOR]

Smart farms are crucial in modern agriculture, but current object detection algorithms cannot detect chili Phytophthora blight accurately. To solve this, we introduced the YOLOv8-GDCI model, which can detect the disease on leaves, fruits, and stem bifurcations. The model uses RepGFPN for feature fusion, Dysample upsampling for accuracy, CA attention for feature capture, and Inner-MPDIoU loss for small object detection. In addition, we also created a dataset of chili Phytophthora blight on leaves, fruits, and stem bifurcations, and conducted comparative experiments. The results manifest that the YOLOv8-GDCI model demonstrates outstanding performance across a gamut of comprehensive indicators. In comparison with the YOLOv8n model, the YOLOv8-GDCI model demonstrates an improvement of 0.9% in precision, an increase of 1.8% in recall, and a remarkable enhancement of 1.7% in average precision. Although the FPS decreases slightly, it still exceeds the industry standard for real-time object detection (FPS > 60), thus meeting the requirements for real-time detection. [ABSTRACT FROM AUTHOR]

Anthropogenic nitrogen (N) addition has increased soil nutrient availability, thereby affecting ecosystem processes and functions in N-limited ecosystems. Long-term N addition decreases plant biodiversity, but the effects of short-term N addition on soil microbial community is poorly understood. The present study examined the impacts of short-term N addition (NH4NO3) on these factors in a sandy grassland and semi-fixed sandy land in the Horqin Sandy Land. We measured the responses of soil microbial biomass C and N; on soil β-1,4-glucosidase (BG) and β-1,4-N-acetylglucosaminidase (NAG) activity; and soil microflora characteristics to N additions gradient with 0 (control), 5 (N5), 10 (N10), and 15 (N15) g N m-2 yr-1. The soil microbial biomass indices, NAG activity, and soil microflora characteristics did not differ significantly among the N levels, and there was no difference at the two sites. The competition for N between plants and soil microbes was not eliminated by short-term N addition due to the low soil nutrient and moisture contents, and the relationships among the original soil microbes did not change. However, N addition increased BG activity in the N5 and N10 additions in the sandy grassland, and in the N5, N10, and N15 additions in the semi-fixed sandy land. This may be due to increased accumulation and fixation of plant litter into soils in response to N addition, leading to increased microbial demand for a C source and increased soil BG activity. Future research should explore the relationships between soil microbial community and N addition at the two sites.