Relationship between impact energy and compression toughness energy of high-strength fiber-reinforced concrete

A simple, economical, and practical drop-weight impact testing machine was developed to determine the impact resistance for high-strength fiber-reinforced concrete (HSFRC) composite. Impact and compression tests were carried out on concrete cylinders reinforced with three different aspect ratios of hooked-end steel fibers l/d (length/diameter): 60, 75, and 83 (30/0.50, 60/0.80, and 50/0.60 mm/mm), and four different percentages of steel fibers 0.5%, 1.0%, 1.5% and 2.0% by volume of concrete. For each aspect ratio and volume of fibers, complete stress–strain curves of HSFRC were generated in order to determine the total energy absorbed for each cylindrical specimen in compression. The addition of steel fibres to concrete has improved impact resistance and also the compression toughness. The test results showed that a logarithmic relation exists between compression toughness energy (E_Ct) by means of the generated stress–stress curves from the compressive tests and the impact energy (E_I) by means of the modified impact machine for HSFRC at different l/d ratio of 60, 75, and 83.     

Direct liquefaction of different lignocellulosics and their constituents: 1. Fractionation,elemental composition

Oils have been produced thermochemically from the following lignocellulosic materials by applying constant hydrogenolytic conditions in an aqueous phase with palladium as catalyst : spruce and birch wood, spruce and birch holocellulose, cellulose, pine bark, spruce and bagasse organosolv lignins, and birch Willstätter lignin. The liquid products were separated into water-, acetone- and dichloromethane-soluble (oil) fractions. The highest oil yield was obtained from spruce organosolv lignin (64%) and the lowest from carbohydrates and pine bark (20–31%). The oils were separated into neutral, strongly acidic and weakly acidic fractions by a liquid/liquid extraction procedure. Sequential elution by solvent chromatography was used for additional comparative characterization of the oils. Calorific values of the feedstocks and oils were calculated based upon the data of elemental analysis.     

成都春季复合污染下PM2:5 的化学消光贡献

为探讨复合污染条件下气溶胶的消光特性, 选取成都市 O3 与 PM2:5 同步污染的春季开展气溶胶组分与消光 特性观测, 并结合美国 IMPROVE 化学消光算法研究了组成与消光特征的关系。结果表明, 2018 年春季成都 PM2:5 平 均浓度与散射系数 bsp 分别为 (50.3±22.4) µg·m−3 和 (237.5±140.2) Mm−1, 且二者均呈现“单峰单谷”的日变化趋势; 大 气气溶胶的消光系数为 (268.4±153.7) Mm−1, 对其贡献最大的组分是 NH4NO3 (26.0%) 和有机物 (OM) (24.4%)。分析 表明在 PM2:5 与 O3 复合污染情况下, 二次污染组分 SNA (SO42−、 NO3−、 NH4+ 三者之和)、二次有机碳 (SOC) 的含量 显著增加, 与清洁天相比分别升高了 1.0 和 1.3 倍; OM 成为最大消光贡献者 (32.2%), 其次是 NH4NO3 和 (NH4)2SO4, 分别贡献 22.8% 和 20.5%。因此, 进一步减少气态前体物如 SO2、 NOx、 NH3 和 VOCs 的排放可以有效改善成都地区 空气质量和能见度。     

基于进化算法的湖泊富营养化投影寻踪回归预测模型

为了建立湖泊富营养化预测模型,选择了与水质富营养化关系密切的工业废水排放量、城市生活污水排放量、农业面源污染负荷比等影响因子及工业废水达标排放率、生活污水处理率等因素作为湖泊富营养化的预测建模指标,建立了基于投影寻踪回归（PPR）的富营养状态的综合指数预测模型。通过把PPR模型表示为直观的参数矩阵形式,用对参数矩阵的优化运算替代传统PPR的多重平滑回归计算技术,简化了运算。结合太湖周边社会、经济影响因子有关资料和太湖水质指标数据,采用粒子群算法(PSO)和免疫进化算法(IEA)对模型中的参数进行优化,得到优化后适用于太湖富营养化综合指数的PPR预测模型。对太湖未来的富营养状态发展趋势进行了预测,结果表明,若不加大治理力度,未来5～30年内太湖富营养化有逐渐加重趋势,因而提出了防治太湖富营养化进一步恶化的调控方案,可为太湖水质富营养化的治理和决策提供参考依据。     

Electrical properties of electroless NiP thin films

The influence of the pH and temperature of the electroless solution on the electrical characteristics of the deposited NiP thin films has been determined. The phosphorous content of the films increases when the pH of the solution is decreased giving rise to a diminution of the temperature coefficient of the resistance (TCR). Low TCR films (TCR ⩽ 100 ppm °C⁻¹ are obtained for pH = 3.4. In this pH range the deposition rate can be increased by heating the electroless solution to moderate temperatures.     

Preparation,characterization, and properties of Pt/Al2O3/cordierite monolith catalyst for hydrogen generation from hydrolysis of sodium borohydride in a flow reactor

High-purity hydrogen can be generated by hydrolysis of sodium borohydride and used for operating portable proton exchange membrane fuel cells. The monolith supported catalyst is suitable for practical NaBH₄-based hydrogen generation system due to its simple reactor structure miniaturizing for small size applications and easy separation from the spent solution. In the present study, a structured catalyst was prepared by wash-coating the Al₂O₃ sol over the wall of cordierite monolith followed by depositing Pt using incipient wet impregnation method; then the monolithic catalysts were characterized by XRF, XRD, SEM, HRTEM and XPS. The catalytic activity of the Pt-based monolithic catalyst towards hydrolysis of NaBH₄ was tested using a flow reactor under ambient conditions in an autothermal manner. The characterization results show that Pt nanoparticles are highly dispersed on the surface of the Al₂O₃-coated layer. A continuous and stable hydrogen generation can be obtained by feeding the reactant (10 wt% NaBH₄–5 wt % NaOH) into the tube reactor loaded with the monolithic catalyst at feed rates of 0.5–2.0 mL min⁻¹.     

Ultrahigh storage density achieved with (1-x)KNN-xBZN ceramics

A series of (1-x)K_0.5Na_0.5NbO₃-xBa(Zn_1/3Nb_2/3)O₃ ((1-x)KNN-xBZN) nanostructural ceramics was successfully synthesised via solid-state reactions. These nanostructural ceramics exhibited high energy storage density compared with pure KNN ceramics. Further analysis of their dielectric/ferroelectric properties and structures revealed that the addition of BZN alloy disrupted the long-range order of the ferroelectric lattice of pure KNN and favoured the formation of ferroelectric islands and/or polar nano-regions. Consequently, the nanostructured ceramic with x = 0.05 exhibited ultrahigh energy storage density, W, of approximately 9.14 J/cm³ and recoverable energy storage density, W_rec, of approximately 4.87 J/cm³ under a fairly low applied electrical field (220 kV/cm). These values exceed the highest values ever reported for KNN-based bulk ceramics. In addition, both excellent fatigue endurance (10⁵ cycles) and temperature stability (Δε'/ε_100°C < 15 % in the range 30–390 °C) were realised with the 0.97KNN-0.03BZN ceramic. Their excellent energy storage properties render KNN-based ceramics potential candidates for application in pulsed-power systems.     

Enhanced thermodynamic properties of ZrNiH3 by substitution with transition metals (V,Ti, Fe,Mn and Cr)

First-principles calculations based on Plane-Wave Self-Consistent Field (PWSCF) method, implemented in quantum espresso program, have been performed on ZrNiH₃ substituted with transition metals (V, Ti, Fe, Mn, and Cr). The study aims to investigate the heat of formation in terms of material stability and desorption temperature. It is found that the substitution by transition metals, results in a significant enhancement in the thermodynamic properties accompanied by an increase of the volumetric and gravimetric hydrogen storage capacities. In addition, the obtained values of heat of formation and desorption temperature corroborate with that required by the U.S. Department of Energy (DOE) for stability and volumetric capacity criteria. Moreover, Mn and Fe elements are found to present the lowest substituting content (34%) to obtain optimum hydrogen storage characteristics (enthalpy of formation of - 40 kJ/mol.H₂, decomposition temperature of 300 K and volumetric capacity of 134 g.H₂/l), without affecting the electronic structure and the metallic character of ZrNiH₃.     

Application of near-infrared absorbing heptamethine cyanine dyes as sensitizers for zinc oxide solar cell

Novel near-infrared absorbing heptamethine cyanine dyes derived from indole, benzoxazole, benzothiazole, and quinoline were synthesized and examined as sensitizers for a zinc oxide solar cell. A 2-carboxyphenylthio-substituted indolium heptamethine cyanine dye showed incident photon-to-current efficiency (IPCE) of 4.17% at 804 nm.