Application of robust machine learning methods to modeling hydrogen solubility in hydrocarbon fuels

Having accurate information about the hydrogen solubility in hydrocarbon fuels and feedstocks is very important in petroleum refineries and coal processing plants. In the present work, extreme gradient boosting (XGBoost), multi-layer perceptron (MLP) trained with Levenberg–Marquardt (LM) algorithm, adaptive boosting support vector regression (AdaBoost?SVR), and a memory-efficient gradient boosting tree system on adaptive compact distributions (LiteMORT) as four novel machine learning methods were used for estimating the hydrogen solubility in hydrocarbon fuels. To achieve this goal, a database containing 445 experimental data of hydrogen solubilities in 17 various hydrocarbon fuels/feedstocks was collected in wide-spread ranges of operating pressures and temperatures. These hydrocarbon fuels include petroleum fractions, refinery products, coal liquids, bitumen, and shale oil. Input parameters of the models are temperature and pressure along with density at 20 °C, molecular weight, and weight percentage of carbon (C) and hydrogen (H) of hydrocarbon fuels. XGBoost showed the highest accuracy compared to the other models with an overall mean absolute percent relative error of 1.41% and coefficient of determination (R²) of 0.9998. Also, seven equations of state (EOSs) were used to predict hydrogen solubilities in hydrocarbon fuels. The 2- and 3-parameter Soave-Redlich-Kwong EOS rendered the best estimates for hydrogen solubilities among the EOSs. Moreover, sensitivity analysis indicated that pressure owns the highest influence on hydrogen solubilities in hydrocarbon fuels and then temperature and hydrogen weight percent of the hydrocarbon fuels are ranked, respectively. Finally, Leverage approach results exhibited that the XGBoost model could be well trusted to estimate the hydrogen solubility in hydrocarbon fuels.     

Electromagnetic transients in the control system of output parameters of a solar power plant in Tajikistan Central Asia region

At present, as the demand for electricity increases in all sectors, there is an urgent need to introduce alternative renewable energy sources into modern energy systems. Renewable energy sources, which consist of solar (photovoltaic, PV), wind and hydro power, are key alternative sources of “green energy’’ energies, but it can also be used to produce “green” hydrogen. Thanks to scientific and technological progress, the cost of photovoltaic solar radiation converters is constantly decreasing at a high rate, which makes it possible to build solar power plants of sufficiently large capacity. In the coming decades, solar energy will become an incentive for the economic development of countries that have the maximum “solar” resource. The Republic of Tajikistan is one of these countries with a high potential for solar energy.The article presents an analysis of the resources and potential of solar energy in the Republic of Tajikistan. The study of electromagnetic transients in networks with photovoltaic solar power plants is performed. The main equations, simulation model and calculations of transients are presented, taking into account changes in voltage on DC buses. An algorithm for controlling the system of automatic control of output parameters is proposed. The analysis of dynamic and static modes in parallel operation of a solar power plant with the grid is carried out. A block diagram and computer model is constructed in the MATLAB package together with Simulink and Power System Blockset.     

Nanofiber structured oxygen defective CoFe2O4-x catalyst for the water-gas shift reaction in waste-to-hydrogen processes

Waste-to-hydrogen processes are a way to produce hydrogen from waste and reduce the amount of landfill/incineration of wastes simultaneously through the gasification of waste. The water-gas shift (WGS) reaction is a key step in this waste-to-hydrogen process by removing the CO and producing additional H₂. A nanofiber-structured CoFe₂O₄ catalyst was synthesized by the electrospinning method, and the catalytic performance in WGS using waste-derived synthesis gas was compared with that of catalysts prepared by sol-gel, hydrothermal, and co-precipitation methods. The CoFe₂O₄ catalyst synthesized by the electrospinning method showed a clear nanofiber structure and revealed a superior redox property. This superior redox property, which has a large relation with the high oxygen storage capacity of the catalyst, induced the formation of an active phase (Co⁰ and Fe₃O₄) in CoFe₂O₄. As a result, the nanofiber structured oxygen defective CoFe₂O_4-x prepared by the electrospinning method showed the best catalytic activity in this study.     

内含实体对H型垂直轴风力机气动性能的影响

以H型垂直轴风力机及其内含圆柱形实体为研究对象,对NACA0018翼型的五叶片H型垂直轴风力机的气动性能进行数值模拟和实验验证。分析8种不同直径的内含圆柱体,在内含实体截面积占风轮迎风面积之比分别为21.2%、50.0%和76.9%时,风力机风能利用率的峰值分别下降8.04%、20.7%及74.3%。结果表明：随着内含实体直径的增大,风能利用率的峰值逐渐减小,开始较为缓慢,达到一定值时快速下降。小直径内含实体主要影响叶片在下风区的转矩,对风能利用率的影响较小,而大直径内含实体还会影响叶片在上风区的转矩,其风能利用率迅速减小。对于内含固定直径的实体,比如在现有建筑物外侧安装风力机时,其风轮半径的选择需综合考虑风能利用率和风力机的建造成本两方面的因素。研究结果可为建筑物与垂直轴风力机进行有效结合以提高风能的利用提供参考。     

Flash Lamps as Ignition and Initiation Sources of the VS-2 Pyrotechnic Composition

In the present work it is found that the pyrotechnic composition VS-2 can be initiated with flash lamps IFC-500 and EVIS. VS-2 pyrotechnic composition contains 90% of mercury（Ⅱ） 5-hydrazinotetrazolate perchlorate and 10% of optically transparent copolymer of 2-methyl-5-vinyltetrazole and methacrylic acid （PVMT）. We have found that the flash lamps make it possible to initiate combustion of VS-2 composition with its transition to detonation both in cylindrical charges placed in brass caps of 5 mm diameter and 2 mm high， and film charges with 10 mm×80 mm in size and surface weights of 60 mg·cm^-2 and 90 mg·cm^-2， showing ignition delay times 10 μs and 3 μs， respectively. We also measured detonation velocities for VS-2 composition film charges， which were 4375-4505 m·s^-1 （of the charge being surface mass 60 mg·cm^-2） and 4221-4281 m·s^-1 （of the charge being surface mass 90 mg·cm^-2） and their blasting action on the aluminum plate. The depths of the normal shock wave imprints at the charge-barrier interface were 0.6-0.7 mm （for surface mass of the film charges 60 mg·cm^-2） and 1.2-1.3 mm （for surface mass of the film charges 90 mg·cm^-2）.     

Physiochemical structure of semicoke derived from co-carbonization of coal and sawdust blends

The substitution of coal blending with sawdust had been widely investigated for metallurgical coke production. In this paper, the physiochemical structures of the semicoke derived from sawdust/coals blends co-coking were characterized by several analytical techniques including FTIR-ATR, XPS, NMR, OM, and SEM. Meanwhile, the influence of the sawdust on the physicochemical properties of the sawdust/coals blends were also investigated. Results indicated that partial substitution of coal blending with sawdust benefited from the formation of colloid and optical anisotropy due to the positive synergetic effect, whereas high proportion of sawdust (>10 wt%) inhibited the agglomeration of semi-coke. On the other hand, the semicoke consisted primarily of aromatic carbons replaced by the oxygen linked to carbons and aliphatic carbons when the coal blending was replaced by high proportion of sawdust, causing a less polyaromatic graphite-like structure formation in the semicoke.     

Vision-related quality of life with myopia management: A review

The disease of myopia has come into focus as a worldwide public health concern. Myopia has shown increasing prevalence, incidence at earlier age and progression to a higher degree. Progressive increase in degree of myopia is strongly associated with increase in axial length of the eye. Various interventions have been shown to slow axial elongation in children. These interventions have been studied to assess efficacy in slowing axial elongation and correction of vision. In addition, research into quality of vision, risk of adverse events, overall safety and impact on vision-related quality (VR-QoL) of life has been pursued. In contrast, studies have been published to demonstrate the risks of myopia, high myopia and increased axial length. This review will discuss VR-QoL assessment on the most effective and most commonly prescribed interventions to slow axial elongation and myopia progression. The patient attributes considered are VR-QoL scores from validated instruments. The development and use of validated survey instruments to assess the patient-reported outcomes is discussed. The review demonstrates that there are numerous factors that may impact VR-QoL to evaluate in the decision-making process when eye care providers consider when, how and if to prescribe myopia management (MM) for children with myopia.     

Preparation and properties of AZO/PS/AZO tri-layer transparent conductive film with a light-trapping structure

The light-trapping structure is an effective method to increase solar light capture efficiency in the solar cells. In this study, Al-doped ZnO (AZO)/polystyrene (PS)/AZO tri-layer transparent conductive film with light-trapping structure was fabricated by magnetron sputtering and liquid phase methods. The structural, optical and electrical properties of the AZO films could be controlled by different growth conditions. When the sputtering pressure of the under-layer AZO film was 0.2 Pa, the discharge voltage was around 80 V, which was within the optimal process window for obtaining AZO film with high crystallinity. The optimal under-layer AZO film had a large surface roughness and a very low static water contact angle of 75.71°, promoting the relatively uniform distribution of PS spheres. Under this sputtering condition, the prepared AZO/PS/AZO tri-layer film had the highest crystallinity and least point defects. The highest carrier concentration and Hall mobility are 3.0 × 10²¹ cm^-3and 5.39 cm² V^-1 s^-1, respectively. Additionally, a transparent conductive film with the lowest resistivity value (3.88 × 10^-4 Ω cm) and the highest average haze value (26.5%) was obtained by optimizing the process parameters. These properties were comparable to or exceed the reported values of surface-textured SnO₂-based as well as ZnO-based TCOs films, making our films suitable for transparent electrode applications, especially in thin-film solar cells.     

Structural,optical, and electrical properties of tin iodide-based vacancy-ordered-double perovskites synthesized via mechanochemical reaction

Over the recent past, lead-based halide perovskite materials have drawn significant attention due to their excellent optical and electrical properties for solar cells and optoelectronics applications. However, the toxicity of lead elements and instability under ambient conditions leads to develop alternative compositions. Herein, we report a novel mechanochemical synthesis of tin iodide-based double perovskites (A₂SnI₆; A = Rb⁺, Cs⁺, methylammonium, and formamidinium), and their structural, optical, and electrical properties are investigated. Importantly, we found that the hydrogen iodide (HI) addition during the ball-milling process minimizes secondary phase formation in the synthesized A₂SnI₆ powders. The effects of HI addition and the A-site substitution are investigated with respect to the lattice parameters, optical bandgaps, and electrical properties of the synthesized perovskite materials. Our results demonstrate essential information to improve the understanding of halide perovskite materials and develop efficient lead-free perovskite photoelectric devices.