有色金属矿山工程技术项目尾款催收管理研究

依托实践经验和教训，从业务角度分析研究有色金属矿山工程技术项目尾款拖欠的形成机理和催收要点，全寿命周期探讨该类经营管理问题的解决途径，结合业务、财务、法务专业知识，提出一系列有深度可借鉴的见解及措施,如：1）催收工作要注意客户性质、客户经营情况、客户人员变化、项目完成瑕疵、乙方管理特征等具体情况采用不同的催收沟通办法；2）建议利用奖惩激励、诉前保全、信用保险、商业保理等工具达到催收或出表目的；3）提醒进行财产损失处理来结束确认不能回收项目的内部管理流程；4）提议利用履约担保、质量担保、客户分级管理等措施来控制回款风险。     

用于低损耗特种玻璃熔炼的高纯致密锆英石的研制

以纯度大于99.9%(质量分数)的高纯ZrO₂和SiO₂为原料,少量TiO₂为添加剂,采用高温固相法合成高纯锆英石(ZrSiO₄)粉料。研究温度和反应时间对高纯锆英石合成效率的影响,发现粒度小于50 μm的原料粉末经1 500 ℃反应48 h后,ZrSiO₄相的含量可以达到95.77%(质量分数)。将合成的高纯锆英石粉料球磨并冷等静压成型后,在1 550 ℃高温烧结成高纯致密锆英石砖。高纯致密锆英石中杂质Fe的含量仅为29 μg/g,Cu的含量小于1 μg/g,是普通商用致密锆英石的1/10;对磷酸盐玻璃静态光吸收损耗的影响仅为普通致密锆英石材料的1/3。将这种高纯致密锆英石材料用于激光玻璃窑炉,有助于降低玻璃对1 053 nm激光的损耗,提升激光玻璃的激光性能。     

Halogenation effect promoted low bandgap polymers based on asymmetric isoindigo unit with low energy loss

To optimize the energy levels of the structural framework of isoindigo polymers, a series of asymmetric isoindigo based low bandgap polymers with chlorine, fluorine and thiazole substituents was constructed and their optical, electrochemical and photovoltaic properties were comparatively evaluated for the impact of different substitutions. In comparison with the polymer based on 2,2'‐bithiophene and isoindigo unit (PTi) with non‐substituted bithiophene as the donor moiety, the highest occupied molecular orbital energy level for the newly synthesized polymers is significantly decreased, and in turn an improvement of the open‐circuit voltage (V_OC) is noted in the corresponding photovoltaic devices. More importantly, combined with a low bandgap of 1.32 eV, the energy losses (E_loss) could be reduced to 0.61 eV for polymer based on chlorinated 2,2'‐bithiophene and isoindigo unit (PCl). In addition, the halogen moieties are observed to be superior in device fabrication and give better values than the thiazole substituent. Both fluorinated and chlorinated polymer donors exhibited improved performance compared with the original polymer PTi. Consequently, this work not only presents the influence of different electron withdrawing substituents on the physicochemical and photovoltaic performance, but also backs the concept of how to reduce the energy loss via the heteroatom effect. © 2020 Society of Chemical Industry     

Selective hydrogenation of levoglucosenone over Pd/C using formic acid as a hydrogen source

Selective hydrogenation of lignocellulosic biomass-derived chemicals is of great importance for future energy and chemical supply. So far formic acid is considered as one of the most promising materials for hydrogen storage. Herein, we report a novel pathway for the hydrogenation of Levogluosenone (LGO), a biorenewable platform chemical, to dihydrolevoglucosenone (Cyrene) and levoglucosanol (Lgol) using formic acid as a hydrogen source. Testing with typical hydrogenation catalysts indicated the crucial influence of the type on reaction selectivity and identified Pd/C as the most suitable catalyst. Among solvents screened, THF in combination with Pd/C showed the best performance for LGO hydrogenation, producing Cyrene in >99% yield at a low temperature (60 °C). Nevertheless, hydrogenation of Cyrene to Lgol required a harsher condition as a result of the difficult reduction property of its C=O bond. Elevating the reaction temperature to 180 °C and increasing double Pd dosage enabled a high yield of Lgol, attaining to 94.8%.     

计及损耗的双馈感应风力发电机高电压穿越控制策略

利用换向原理分析其电磁暂态特性，在此基础上，对DFIG输出无功功率与其铜损耗的解析关系进行了理论分析，推导出了使铜损耗最低的DFIG输出无功功率最优参考值。同时，转子的瞬时功率补偿分量减小了DC总线电压的波动，从而减少了转换器的功率损耗。由此，提出了考虑DFIG铜损和转换器损耗的DFIG高电压穿越控制策略。仿真结果表明，该控制策略可以在保证DFIG高电压穿越能力的同时降低DFIG铜损耗与换流器损耗，并具有较好的暂态特性。     

入口弯管对矿用轴流通风机气动性能影响的数值研究

以某大型矿用低压轴流式通风机为研究对象, 采用气体动力学性能试验和数值模拟的方法研究了不同入口弯管对风机性能的影响, 重点分析了入口弯管引起的叶轮内部流动特征和损失分布的变化规律。研究结果表明, 风机入口采用弯管连接缩短了进口管道的轴向长度, 节省了地下空间, 但同时来流的均匀性受到影响。弯管内气流速度梯度较大, 管道内侧易发生流动分离, 产生回流区, 增大了流体流动时的能量损失, 风机的整体性能下降。弯管与叶轮入口之间的连接长度会影响内部流场, 当附加直管段较长时, 来流均匀性得到提高, 风机性能有所改善。     

水性锈转化涂料的制备及性能

采用苯丙乳液与改性苯丙乳液共混作为成膜物质,以单宁酸为转锈剂,柠檬酸为配位剂,焦性没食子酸为转锈促进剂,再加入成膜助剂、有机胺类缓蚀剂、渗透剂等,制备了一种可应用于带锈钢材的水性锈转化涂料。通过正交试验和单因素试验确定了涂料的最优配方为:成膜物质65%,转锈剂5%,转锈促进剂2%,缓蚀剂0.6%,渗透剂2%,配位剂0.5%,成膜助剂1.6%,蒸馏水余量。采用塔菲尔极化曲线测量、中性盐雾试验和盐水浸泡试验考察了漆膜的耐蚀性。结果表明,所制水性锈转化涂膜可耐盐雾96 h,耐盐水浸泡168 h,且耐酸性较强,在pH为2的3.5%NaCl溶液中有保护作用。与两款市售涂料相比,该自制水性锈转化涂料具有更好的耐蚀性。     

Catalytic dehydrogenation of formic acid-triethanolamine mixture using copper nanoparticles

In a bid to complement the lost reserves from fossils, recent advances in research are tailored towards producing hydrogen as an alternative source of fuel which is aimed at fostering a globally sustainable and reliable energy-economy. In this work, hydrogen was produced from formic acid (FA) using a new technology that involves the use of copper nanoparticles (CuNPs) supported on triethanolamine. The CuNP-catalysts of variant concentrations (i.e. 0.6–1.2 M) were synthesized using the conventional chemical deposition method. Also, a novel approach that bothers on the application of the Differential Method of Analysis (DMA) was used in determining the kinetic parameters for the FA-dehydrogenation. Based on the results, the volume of H₂ produced varied with time, pH, concentration and catalyst-size. At 6 h, the 1 M CuNPs gave the highest volume (815 mL) of hydrogen with corresponding pH, particle size and approximate conversion of 3.19, 1.5 nm and 100% respectively, whereas, over extended periods i.e. over 6 h, the approximate volume-conversions of FA increased insignificantly for all catalysts. According to the investigation, the optimum CuNP-catalyst concentration required to produce 815 mL H₂ in 6 h is 1 M. The decomposition was a first-order-type with a rate constant (k-value) of 1.0041 s⁻¹.     

Rapid polymerization synthesizing high-crystalline g-C3N4 towards boosting solar photocatalytic H2 generation

Graphitic carbon nitride (g-C₃N₄) is a promising metal-free photocatalyst for solar photocatalytic hydrogen gas (H₂) generation from water. In particularly, high-crystalline g-C₃N₄ (GCN-HC) material with fewer structural defects possesses the fast photoexcited electron-hole pair's separation efficiency as comparison with bulk g-C₃N₄ (GCN-B) powders, leading to the drastic improvement of photocatalytic activity. However, the fabrication of such GCN-HC photocatalyst by a simple and economical synthesis approach still remains a challenge. Herein, we firstly develop a one-step rapid polymerization strategy for synthesizing the GCN-HC, that is direct calcination of melamine at 550 °C not only without the early heating process, but also without the assistance of any additive or salt intercalation. As a result, the GCN-HC exhibits an obviously boosting visible-light-induced photocatalytic H₂-generation performance, which is over 2.06-folds much greater than that of GCN-B. Our work provides an available one-step synthetic strategy for the large-scale preparation of high performance GCN-HC towards sustainable solar-to-chemical energy conversion.     

Fabrication of platinum thin films for ultra-high electrocatalytic hydrogen evolution reaction

While the noble metals (e.g., platinum, (Pt)) remain the benchmark electrocatalyst for the hydrogen evolution reaction (HER), their mass production require a reduced metal loading and faster fabrication protocols. The aim of the present work is to prepare Pt thin films by simple and fast fabrication technique, and to evaluate their performance for HER. The thin films of Pt are grown on two substrates, namely titanium foil (Ti) and nickel foam (NF), using a single step aerosol assisted chemical vapor deposition (AACVD) method. The film deposition time are varied from 20 to 60 min. Microscopic analyses suggest a gradual evolution of the films into percolated and/or porous nanostructures, a feature that remains highly desired to allow the maximum access of active sites. The performance of the as-prepared electrodes is evaluated by monitoring the HER in acidic electrolyte. The Pt film on nickel foam (Pt/NF) exhibits better electrical conductivity and smaller charge transfer resistance, while the film deposited on the Ti foil (Pt/Ti) demonstrates superior catalytic activity per active sites. The as-prepared Pt/Ti and Pt/NF electrodes produce 10 mA cm⁻² at overpotential of 28 mV and 26 mV, respectively, better in performance than commercial Pt/C electrode (~39 mV), set a new bench mark electrocatalyst for the HER.