现代电力电子器件

本文简单回顾了电力电子技术及电力电子器件的发展过程,介绍了IGBT、IGCT等主流现代电力电子器件的工作原理、现状和发展动态。最后,展望了现代电力电子器件的未来发展。     

飞机维护清洗中的1,1,1-三氯乙烷溶剂淘汰技术

主要介绍飞机维护中的清洗分类、消耗臭氧层物质1,1,1-三氯乙烷溶剂在飞机维护清洗中的使用方面目前存在的替代1,1,1-三氯乙烷的主要技术（水基和半水基清洗、非为DS有机溶剂清洗和其它清洗技术）,以及在飞机维护清洗不同分类中的可以采用的替代技术的选择。     

非洲兰花香素的合成

非洲兰花香素的关键香气成分是 3 甲基辛酸甲酯。以巴豆酸为原料经酯化反应及在CuI催化条件下的Michael加成反应两步制备出目标物 ,总产率可达到 6 1%     

Plant-Growth Inhibitory Activity of Cedrelanolide from Cedrela salvadorensis

The effect of cedrelanolide, the most abundant limonoid isolated from Cedrela salvadorensis (Meliaceae), was assayed as a plant-growth inhibitory compound against monocotyledonous and dicotyledonous seeds. This compound inhibited germination, seed respiration, and seedling dry weights of some plant species (Lolium multiflorum, var. Hercules, Triticum vulgare, var. Salamanca, Physalis ixocarpa, and Trifolium alexandrinum). Our results indicate that cedrelanolide interferes with monocot preemergence properties, mainly energy metabolism of the seeds at the level of respiration. In addition, the compound inhibits photophosphorylation, H⁺ uptake, and noncyclic electron flow. This behavior might be responsible for its plant-growth inhibitory properties and its possible role as an allelopathic agent.     

Behavior of Paramagnetic Iron during the Thermal Transformations of Kaolinite

Kaolinites with various degrees of structural order and iron content were heated and subsequently analyzed via electron paramagnetic resonance. Iron was present in two different states in the heated materials, either as dilute structural Fe³⁺ ions or in concentrated Fe³⁺ phases. During metakaolinization, the environment of dilute Fe³⁺ ions changed, following modifications of the Al³⁺ coordination, and the Fe³⁺ concentration increased. With the breakdown of metakaolinite, the diffusion of Fe³⁺ ions induced their exsolution in superparamagnetic iron-rich domains (Fe³⁺ clusters in γ-Al₂O₃ and/or Fe³⁺ oxide nanophases), which produced a decrease in the dilute Fe³⁺ concentration. The subsequent breakdown of γ-Al₂O₃ and the formation of mullite made the dilute Fe³⁺ concentration increase again, because of the incorporation of Fe³⁺ ions in the mullite structure.     

Grain-Size Effect on Compressive Creep of Silicon-Carbide-Whisker-Reinforced Aluminum Oxide

The steady-state compressive creep of Al₂O₃ with 10 vol% SiC whiskers having grain sizes of 1.2, 2.3, and 4.0 μm has been measured at 1400°C in argon. The creep rate is related to the free volume within the whisker network, not the nominal grain size. The results are consistent with diffusional-controlled creep with different contributions from grain-boundary sliding. Under low stresses, only Liftshitz sliding is possible and the diffusional process controls deformation, while at stresses over a threshold, Rachinger sliding is the mechanism controlling deformation. The evolution between Liftshitz and Rachinger sliding is marked by a significant increase in the value of the stress exponent.     

60%精喹禾灵WG防除杂草试验及增效剂筛选

防除棉花田杂草的田间试验表明,60%精喹禾灵WG在150～180 g/hm2剂量下对马唐、稗草、牛筋草等棉花田主要一年生禾本科杂草具有很好的防效,防效达90%以上,对茅草和芦苇等多年生禾本科杂草抑制作用明显.同时在氮酮、有机硅和乙氧基脂肪胺等增效剂筛选试验中,有机硅(45 g/hm2)对60%精喹禾灵WG增效作用显著,杂草防效提高2%～15%.     

电网投资项目全过程后评价体系研究

根据电网建设项目建设阶段划分及华北电网有限公司电网基建项目评价重点,建立了系统完整的电网投资项目全过程指标体系、评价模型和方法,该体系可以减轻相关业务人员面对数量庞大、过程复杂的电网投资项目技术经济分析评价工作,为电网投资项目的决策者、管理者、建设者和运营人员应用合理的方法和策略,提供科学依据与参考。     

超临界水冷堆与WWER1000型压水堆的安全特性比较分析

超临界水冷堆(SCWR)是在高于水的临界点(374℃,22.1 MPa)的温度和压力下运行的反应堆。它的设计为一次通过循环,其中没有再循环回路。这点是与现在运行的轻水堆的最大不同。在超临界水堆电站系统中,以控制棒、汽轮机控制阀与反应堆冷却剂泵为主要的控制方式。通过对比分析超临界水冷堆与田湾核电站WWER1000型压水堆主泵卡轴事故下的安全特性,得出超临界水堆给水流量的丧失会造成反应堆冷却剂流量的丧失,而WWER1000型压水堆给水流量的丧失并不会造成反应堆冷却剂流量的丧失;WW-ER1000型压水堆的安全系统有控制棒、蒸汽发生器的主蒸汽旁排阀、应急给水泵,这些安全配置与超临界水冷堆相似;相比WWER1000型压水堆,超临界水冷堆在压力较快达到稳定状态前提下,其最高包壳温度有个剧烈变化过程,但超临界水冷堆和WWER1000型压水堆在卡轴事故发生后,都能建立稳定的自然循环。     

新型转光剂的制备及在农膜中的应用

通过溶胶－凝胶法将有机荧光机包覆在无机凝胶中,制得了一种新的有机－无机杂化材料。该杂化材料能有效吸收254－365nm范围的紫外光,在约450nm处产生强的蓝色荧光,并具有很好的光热稳定性;与聚乙烯薄膜具有良好的结合力,且不影响薄膜的加工工艺与物理性能;在薄膜加工中原有组分的光学性能基本保持不变。