Improvement of surge current performances of ZnO varistor ceramics via C3N4-doping

ZnO-Bi₂O₃ based varistor ceramics doped with C₃N₄ were fabricated via solid state method. Experimental results show that C₃N₄ additive acts as an inhibitor in ZnO grain growth, and the average grain size decreases from 10.2–7.1 μm. The varistor breakdown voltage gradient increases from 222.3–282.3 V/mm, and the nonlinear coefficient increases from 51.9–58.2 with the increase of C₃N₄ content from 0 to 3.0 wt%. The C₃N₄-added samples exhibited smaller residual voltage ratio and better surge current withstanding capability. It is proposed that the C₃N₄-doping leads to substitution of nitrogen for oxygen in the grain boundary region, forming acceptor type defects. The acceptor type defects act as electron traps, increasing the barrier height from 1.31 to 1.50 eV and the depletion layer width from 54.9–61.8 nm, which increases the nonlinearity, and the surge current performances of the C₃N₄ doped ZnO varistor ceramics are improved.     

Constructing the high-areal-capacity,solid-state Li polymer battery via the multiscale ion transport pathway design

The parasitic Li dendrite formation and retarded ion diffusion dynamics inhibit the deployment of solid-state batteries (SSBs) at high areal capacity loadings. Here, we present the modular design of the Li⁺ percolating network by grafting the ionic-conductive polyether amine (PEA) at the multiple scales: the PEA modified zinc hydroxystannate (PEA@ZHS) (flame retardant units) and polyamide 6 (mechanical rigid units) are coherently introduced to optimize the PEO-based solid electrolyte (PX-PEA@ZHS) with the Young's modulus (3.41 GPa), ionic conductivity (4.29 × 10⁻⁴ S cm⁻¹ at 55 °C) and flame retardancy (22% reduction of heat release rate); on the other hand, PEA molecules are grafted onto the acetylene black additive to establish the dual conductive network, endowing two orders of magnitude increase of ionic conductivity for the high-compaction cathodes. The as-integrated symmetric cell exhibits a critical current density up to 0.8 mA cm⁻² and cycling endurance for 1000 h at 0.2 mA cm⁻²; upon the SSBs assembly with the record high loading of LiFePO₄ (12.4 mg cm⁻²), the high-areal-capacity, cycling stability as well as the extreme temperature endurance till 110 °C are simultaneously realized, which inspire the rational design of commercially feasible, energy-dense, flame-resistance energy storage prototype.     

A review of carbonates as hydrocarbon source rocks: basic geochemistry and oil–gas generation

Carbonates have been known to act as hydrocarbon source rocks, but their basic geochemical and associated hydrocarbon generation characteristics remain not well understood as they occur with argillaceous source rocks in most cases, and the hydrocarbon generation from each rock type is di cult to distinguish, forming one of puzzling issues within the field of petroleum geology and geochemistry. To improve the understanding of this critical issue, this paper reviews recent advances in this field and provides a summary of key areas that can be studied in future. Results show that carbonate source rocks are generally associated with high-salinity environments with low amounts of terrestrial inputs and low dissolved oxygen contents. Petrographically, these source rocks are dark gray or black, fine-grained, stratified, and contain bacterial and algal bioprecursors along with some other impurities. They generally have low organic matter contents, although these can vary significantly in di erent cases(e.g., the total organic carbon contents of marine and lacustrine carbonate source rocks in China are generally 0.1%–1.0% and 0.4%–4.0%, respectively). These rocks contain type I and type II kerogen, meaning there is a lack of vitrinites. This means that assessment of the maturity of the organic matter in these sediments needs to use non-traditional techniques rather than vitrinite reflectance. In terms of molecular geochemistry, carbonate source rocks have typical characteristics indicative of generally reducing and saline environments and lower organism-dominated bioprecursors of organic matter, e.g., high contents of sulfur compounds, low Pr/Ph ratios, and dominance of n-alkanes. Most of the carbonate source rocks are typically dominated by D-type organic facies in an oxidized shallow water mass, although high-quality source rocks generally contain A-and B-type organic facies in saline lacustrine and marine-reducing environments, respectively. The hydrocarbon generation model for the carbonate source rocks can involve early, middle, and late stages, with a diversity of hydrocarbons within these rocks, which can be aggregated, adsorbed, enclosed within minerals, or present as inclusions. This in turn implies that the large-scale hydrocarbon expulsion from these rocks is reliant on brittle deformation caused by external forces. Finally, a number of aspects of these source rocks remain unclear and need further study, including the e ectiveness of carbonates as hydrocarbon source rocks, bioprecursors, and hydrocarbon generation models of carbonate source rock, and the di erences between marine and lacustrine carbonate source rocks.     

Uncertainty analysis of parameters in non‐point source pollution simulation: case study of the application of the Soil and Water Assessment Tool model to Yitong River watershed in northeast China

Uncertainty analysis of the model parameters in non‐point source pollution (NPSP) simulation is important because of its great effects on predictions and decision‐making. Understanding the main parameters that effect the uncertainty of NPSP is necessary to provide the basis for formulating control measures. In this study, two methods were applied to conduct parameter uncertainty analysis for Soil and Water Assessment Tool (SWAT). Sobol’ method was used to screen out the model parameters with great effects on the runoff, sediment, total nitrogen (TN) and total phosphorus (TP). The results obtained by sensitivity analysis were used subsequent model calibration and further uncertainty analysis. Monte Carlo (MC) method was employed to analyse the effects of parameter uncertainty on the model outputs. However, such problems are time‐consuming because the MC method required to invoke simulation model thousands of times. To address this challenge, a kriging surrogate model was developed to improve the overall calculation efficiency. The results obtained by sensitivity analysis showed that curve number value (CN2), soil evaporation compensation factor (ESCO), universal soil loss equation support practice factor (USLE_P) and initial organic nitrogen concentration in soil layer (SOL_ORGN) had significant effects on the SWAT outputs. The uncertainty analysis results showed that the uncertainty of runoff is the lowest, followed by TP and TN, and the uncertainty of sediment was the greatest. The kriging surrogate model has the ability to solve this time‐consuming problem rapidly with a high degree of accuracy, and thus it is very robust.     

基于决策树的羽流追踪机器人自主决策方法研究

针对无法获得可靠羽流流向信息不利于实现羽流追踪的问题，提出了一种基于决策树的羽流追踪移动机器人自主决策方法。该方法通过移动机器人两侧的浓度传感器采集到的浓度信息，利用追踪的行为规则建立决策树模型，获得行为决策信息，使机器人高效地追踪到羽流并精确地定位。由于浓度变化关系蕴含了羽流的流向及流速信息，从而取代了传统方法中流向及流速传感器。在扩散环境下，通过移动机器人羽流追踪实验，实现了良好的源定位效果。     

Eddy Current Detection of Retained Austenite in Ni-Hard4 Cast Iron

In this article, the nondestructive eddy current (EC) method was used for microstructural evaluation of Ni-hard4 cast iron (NiHCI). Different destabilizing heat treatments were used to produce different microstructures and hardness. The microstructural analysis and hardness measurement were done for conventional characterization of the reference blocks. Then, the EC techniques were applied to evaluate the hardness and microstructural changes by the detection of EC parameters at different frequencies. Metallurgical investigations showed that increasing the destabilizing soaking time and temperature decreases the amount of retained austenite in NiHCIs. The nondestructive evaluation method (NDT) revealed that it can be good correlated between retained austenite amount and hardness with EC parameters. This shows that the EC technique can detect NiHCIs products according to the metallurgical characterization with good accuracy.     

Identification of factors that accelerate hydrogen production by Clostridium butyricum RAK25832 using casamino acids as a nitrogen source

The ability of Clostridium butyricum RAK25832 to use casamino acids as a nitrogen source was investigated. Strain RAK25832 showed the capacity to utilize different types of carbon sources. With glucose as a carbon source (10 g/L), the preferred final concentration of casamino acids was 26.67 g/L, with a cumulative hydrogen production, production rate, and yield of 2505 mL H₂/L, 160 mL/h, and 1.81 mol H₂/mol glucose, respectively. Eighteen metal elements were screened to identify the most important metals for biohydrogen production, and four elements were optimized. The optimal medium composition was MgCl₂·6H₂O (0.1 g/L), K₂HPO₄·3H₂O (6.67 g/L), NaHCO₃ (2.6 g/L), and FeCl₂·4H₂O (0.002 g/L). Vitamin supplementation of the medium showed no significant effect on hydrogen production. Under the optimized conditions, cumulative hydrogen production reached 3074 mL H₂/L. This is the first study to demonstrate the use of casamino acids as a nitrogen source by C. butyricum.     

Method to characterize the fire behavior of materials assemblies

The fire behavior of various large samples polymers assemblies is an under‐researched topic. In fire risk assessment, the resultant heat release rate of burning different combustibles has to be known. To highlight interactions between components, 2 types of configurations were tested: juxtaposed and layered materials, using a specific radiant panel setup. For juxtaposed assemblies, results indicated that the more flammable component acted as an accelerator for the global combustion kinetics. For layered assemblies, 2 main phenomena were evidenced: the front material acted as a shield delaying the combustion of the backside material and the presence of a backside material induced a thermal thickening that slowed down the combustion of the front material. The experimental burning behaviors of the assembly were compared with a simulated one calculated from the superposition principle. This method was described by introducing a time offset and/or a slowdown factor in the model, confirmed with the use of different assemblies.     

Facile preparation of ultra-low Pt loading graphene-immobilized electrode for methanol oxidation reaction

Pulse current electrodeposition (PCE) technique was used to prepare graphene-supported platinum nanoparticles (GN-PtNPs) electrodes for the methanol electro-oxidation reaction in acidic media. The influences of the PCE parameters (applied current density, concentration of the Pt precursor, and duty cycle) upon the as-prepared GN-PtNPs electrodes for the methanol oxidation reaction (MOR) in terms of catalytic activity and tolerance against poisoning were studied using the Taguchi design of experiment (DOE). The analysis of variance (ANOVA) and signal-to-noise (S/N) ratio analysis provided prediction of optimal electrodeposition conditions to yield GN-PtNPs electrode which give the best MOR performance. The values of confirmatory experiment were demonstrated close to the values predicted using the Taguchi method. Transmission electron microscopy images showed that the Pt crystallites in flower-like structure were deposited evenly on the surface of graphene sheet. The Pt crystallites were predominantly in a zero-valent, metallic Pt state based on the X-ray photoelectron spectroscopy analysis.