Hollow structured Zn0.76Co0.24S–Co9S8 composite with two-phase synergistic effect as bifunctional catalysts

It is of great significance to develop efficient and inexpensive oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts for the current energy crisis. But this is still a long-term and formidable challenge. In this work, a two-phase synergistic effect between transition metal sulfides is applied in the design of ORR/OER bifunctional catalysts. Co-based zeolite imidazolate framework (MOF) is used as a precursor to prepare the hollow Co₉S₈ through vulcanization and heat treatment. At the same time, the phase transformation occurs to form some Zn_0.76Co_0.24S on surface during the heat treatment due to the Zn-polydopamine coating. The hollow structure Zn_0.76Co_0.24S–Co₉S₈ composite has been verified and promotes the diffusion of reactants and products, and the interaction between two phases greatly promotes the catalytic reactions. The coating of Zn-polydopamine forms uniform carbon layer on surface, enhancing the conductivity of Zn_0.76Co_0.24S–Co₉S₈ composite. The Zn_0.76Co_0.24S–Co₉S₈ composite shows much better performance of ORR and OER compared to any of them. The overpotential of OER at a current density of 10 mA/cm² is 330 mV, and the half-wave potential of ORR is 0.83 V. Additionally, the Zn_0.76Co_0.24S–Co₉S₈ composite displays better cyclic stability. The synergistic effect of Zn_0.76Co_0.24S and Co₉S₈ can be considered as the foremost factor for the improvement of catalyst performance, which provides new possibilities for the development of non-precious metal bifunctional catalysts.     

既有居住建筑附属地下换热站降噪研究

为了降低既有建筑附属用房产生的噪声对居民生活的影响、改善居住建筑声环境,对既有居住建筑附属用房地下换热站的噪声源以及噪声传播途径进行了分析;以既有居住建筑地下换热站室内噪声实测数据为基础,对室内环境的声学特征进行分析。在综合考虑居民的健康和舒适的基础上,提出了针对该附属用房的降噪处理改造设计方案。经过改造后的空间噪声明显降低,空间声环境指标达到标准要求,有效地改善了居住建筑的声环境。文中提出的改造设计方案为制定民用建筑附属用房声学设计标准提供了技术支撑。     

Electrochemical Characterization of Isolated Nitrogenase Cofactors from Azotobacter vinelandii

The nitrogenase cofactors are structurally and functionally unique in biological chemistry. Despite a substantial amount of spectroscopic characterization of protein-bound and isolated nitrogenase cofactors, electrochemical characterization of these cofactors and their related species is far from complete. Herein we present voltammetric studies of three isolated nitrogenase cofactor species: the iron–molybdenum cofactor (M-cluster), iron–vanadium cofactor (V-cluster), and a homologue to the iron–iron cofactor (L-cluster). We observe two reductive events in the redox profiles of all three cofactors. Of the three, the V-cluster is the most reducing. The reduction potentials of the isolated cofactors are significantly more negative than previously measured values within the molybdenum–iron and vanadium–iron proteins. The outcome of this study provides insight into the importance of the heterometal identity, the overall ligation of the cluster, and the impact of the protein scaffolds on the overall electronic structures of the cofactors.     

带权决策表的属性约简

属性约简是粗糙集理论的重要应用。考虑将决策表中的每行都作为一条决策规则时，若把表中出现相同决策规则的次数作为权，可得到带权决策表。提出了关于带权决策表的正域约简相应的辨识矩阵并给出了证明，从而得到了约简算法。相比于决策表中的正域约简时发现，通过将决策表转化为带权决策表后，再利用算法1进行约简时，其在一定程度上优于前者。提出了近似分类精度约简相应的辨识矩阵并给出了证明。对于2个算法，在选取的UCI数据集上进行了实验验证。通过实验进一步说明了所提出算法的可行性和有效性。     

Metallurgical slag properties as a support material for bimetallic nanoparticles and their use in the removal of malachite green dye

Fe-Cu oxides nanoparticles (Nps) were embedded in two steel slag wastes (SSB and SSW) to develop SSB/Fe-Cu and SSW/Fe-Cu nanocomposites. Nps with mean sizes between 10–20 and 6–10 nm on SSW and SSB, respectively are agglomeration with a different shape. Their characteristics were investigated by XRD, TEM, BET, SEM techniques. The Nps modified the morphology of both support materials. XRD pointed out the presence of Cu and Fe. The proportion of Cu concentration was higher than the one of Fe. Nanocomposites were tested in malachite green removal from aqueous solution. The adsorption kinetic indicated physisorption and chemisorption as the main mechanisms of adsorption. The adsorption capacities were 88.26 and 63.55 mg/g for SSW/Fe-Cu and SSB/Fe-Cu, respectively. This novel, easy to prepare and low-cost nanocomposites is an efficient adsorbent material. The presence of calcium compounds may improve Nps deposition an MG removal. Materials with ferric phases are not as efficient as the first one; Fe is not well supported on the material. The removal of MG took place by dye structure modification and by interactions with Cu nanoparticles improving the oxidation-reduction process, through synergic effects.     

Lift-and-project MVEE based convex hull for robust SCED with wind power integration using historical data-driven modeling approach

This paper presents an adjustable robust security constrained economic dispatch (SCED) model with wind power uncertainties. First, the scenario based adjustable robust SCED model is presented. It considers multiple scenarios from historical data as well as the spatial correlation among wind farms. Then, the proposed SCED model becomes an optimization problem with a large amount of constraints which is skillfully solved using a lift-and-project minimum volume enclosing ellipsoid (MVEE) based convex hull. Furthermore, the proposed model is transformed into a second order cone programming (SOCP) model by the use of participation factors to generate adjustable generation outputs and thus guarantee the energy balance. In order to further reduce the computational complexity, the inactive constraints reduction strategy is proposed to quickly eliminate inactive SOC security constraints before solving the model. Numerical results of IEEE 14-bus and 118-bus test systems as well as the practical Polish power systems with several wind farms show that the proposed model can achieve better economies. Moreover, more than 82% of security constraints are identified as inactive in various cases of the simulation, and the proposed inactive constraints reduction strategy is promising for improving the computational performance.     

Preparation of iron and nitrogen co-doped carbon material Fe/N-CCM-T for oxygen reduction reaction

In this paper, iron and nitrogen co-doped carbon material with nanotube structure (Fe/N-C_CM-T) was synthesized by pyrolyzing a mixture of Fe salt, chitosan and melamine and displayed high electrocatalytic performance for oxygen reduction reaction (ORR). The structure of the Fe/N-C_CM-T was characterized and their ORR performance in alkaline media was investigated by linear sweep voltammetry, cyclic voltammetry and chronoamperometry. Fe/N-C_CM-T displayed better ORR performance than other carbon materials like Fe/N-C_C-800. The Fe/N-C_CM-800 with a large surface area (302.5 m²/g) especially exhibited the best ORR electrocatalytic performance among the prepared carbon materials, which was also proved by its similar Tafel slope (76 mV decade^?1) to Pt/C catalyst (74 mV decade^?1). Fe/N-C_CM-800 showed similar ORR activity as commercial Pt/C catalyst, but superior tolerance to methanol and stability. Such high ORR performance of the Fe/N-C_CM-T can be attributed to its nanotube structure, high specific surface area (SSA), high graphitic-N and pyridinic-N contents.     

微纳米银花状球结构的化学制备技术现状与展望

近年来,微纳米银花状球结构的化学制备技术备受人们关注。阐述了微纳米银花状球结构的化学还原沉淀制备技术,探讨化学化学还原沉淀制备花状球的形成机理。银花状球由纳米片或棒等其他纳米形貌构成,因此表现出独特的光、催化等性能,在催化、生物等方面具有巨大潜在应用。     

High-temperature corrosion characteristics of yttria-stabilized zirconia material in molten salts of LiCl-Li2O and LiCl-Li2O-Li

The isothermal and cyclic corrosion behavior of yttria (Y₂O₃)-stabilized zirconia (ZrO₂) in a LiCl-Li₂O molten salt were investigated at 650 °C in an argon atmosphere. During isothermal and cyclic corrosion tests in the molten salt of LiCl-Li₂O for 168 h and 7 thermal cycles, the corrosion rate was very low, whereas under the molten salt of LiCl-Li₂O-Li for 168 h, the corrosion rate was almost 10 times higher than that in the molten salt of LiCl-Li₂O. No corrosion product was detected until 168 h for the isothermal corrosion test, however, after 7 thermal cycles, a very-low-intensity Li₂ZrO₃ peak was detected at the beginning stage of the chemical reaction between ZrO₂ and Li₂O. Additionally, in the molten salt of LiCl-Li₂O-Li for 168 h, a large amount of Li₂ZrO₃ was formed, with evidence of marked cracks, pores, and spallations on the corroded surface. The introduction of Y₂O₃-stabilized ZrO₂ was beneficial in increasing the hot corrosion resistance of the structural materials used to handle molten salts containing Li₂O at elevated temperature without forming a lithium at the cathode during the electrolytic reduction process.