双有源桥钳位变换器的简单PWM移相控制策略

针对传统移相控制方法下双有源桥变换器会产生较大电流应力和在宽电压范围下低效率运行的问题,提出一种面向双有源桥钳位变换器的简单PWM移相控制策略。首先,利用钳位开关的运行周期和占空比取代变换器内移相比,以简化原边H桥工作过程并提高控制自由度。然后,计算了副边H桥开关管的占空比。通过分析所提出的移相控制策略的工作原理和软开关特性,推导出以传输功率标幺值为控制量的线性大信号模型。最后,采用基于TMS320F2808为控制器的实验平台进行验证。实验结果展示了简单PWM移相控制降低了变换器的电压应力和电流应力,显著提升了变换器的传输效率。     

阻燃处理对聚乳酸/竹粉复合材料吸水性能的影响

利用氢氧化铝(ATH)、硅烷改性聚磷酸铵(APP)及APP/ATH复配阻燃剂与聚乳酸(PLA)、竹粉(BF)共混,制备阻燃型PLA/BF复合材料,并对其进行不同时间的浸水处理,测定阻燃型PLA/BF复合材料的吸水率和浸水处理前后的力学性能。结果表明,浸水处理后复合材料的拉伸强度和冲击强度均有不同幅度的降低,其中,APP/ATH复配阻燃剂阻燃型复合材料力学性能下降最显著,浸水4d后,其拉伸强度下降了近90%;APP和ATH单独阻燃的复合材料在浸水过程中的吸水率和吸水厚度膨胀率均较低,而APP/ATH复配阻燃剂阻燃型PLA/BF复合材料的吸水率最高,尺寸稳定性最差。     

弃旧立新——沈阳友谊国际会议中心改扩建设计

本文通过对沈阳友谊国际会议中心改造扩建工程的介绍,表达了在友谊宾馆特定环境下,建筑师对选址、规划、旧建筑、环境、材料材质、功能、空间的综合考虑与关注,将业主需求的新功能理性地“溶解”在旧建筑中,形成与环境特色共生的新建筑。     

阻燃抑烟型聚乳酸/竹粉复合材料性能研究

采用模压成型法制备了氢氧化铝（ATH）、聚磷酸铵（APP）及APP+ATH阻燃型聚乳酸/竹粉(PLA/BF)复合材料,通过扫描电子显微镜考察了复合材料拉伸断面和燃烧后炭层的微观结构,并对其力学性能、热稳定性能和燃烧性能进行了测试。结果表明,阻燃剂的引入均降低了复合材料的力学性能,但显著提高了热稳定性,600 ℃时复合材料的残炭率分别达到了20.3 %、27.9 %和26.3 %;ATH对复合材料具有显著的抑烟效果,但抑热作用较APP要差,而ATH与APP复合阻燃剂使复合材料兼具较好的抑热作用和抑烟效果。     

短历时生态输水条件下的地下水系统响应

为研究短历时生态输水条件下的湿地生态系统响应,以黄河三角洲为例,分析总结了水文地质概念模型,采用Visual Modflow软件构建了短历时生态补水的地下水流数值模型,从地下水水量和水位两方面分析刁口河尾闾生态核心区补水时的地下水系统响应过程及影响范围.结果表明,短历时生态补水条件下周边地区地下水系统响应显著,为该地区生态输水提供了依据.     

Silica islands regulated external Ti-site environment of TS-1 for enhanced performance of 1-hexene epoxidation

Rational regulation of the local environment of Ti-sites in TS-1 harbors tremendous industrial and scientific significance to epoxidation reactions. Herein, we report a facile and environment-friendly strategy to boost catalytic selectivity by covering the Ti-sites on an external surface of TS-1 (ITS-1) without sacrificing activity of internal Ti sites. By a quantitative analysis of d₃-acetonitrile and quinoline-DRIFTS, ¹H MAS NMR and XPS, it is found that the percentage of external Ti-sites decreased from 11% to 6% after depositing surface silica islands. This successfully inhibits ring-opening reaction of 1,2-epoxyhexane on catalyst surface, as demonstrated by slower kinetic decomposition rate of 1,2-epoxyhexane. Compared with conventional TS-1 catalyst, selectivity of 1,2-epoxyhexane over ITS-1 catalyst significantly increased from 83.5% to 98.5% while maintaining high 1-hexene conversion. Furthermore, overmuch surface silica coverage only leads to extremely low conversion (2%) due to inhibition of mass transfer. This work paves the way for rational construction of Ti-containing catalysts for 1-hexene epoxidation.     

利用双折射效应设计的窄带滤光系统

本文根据单轴晶体的双折射效应及偏振光干涉原理，设计制作了一种透射带宽大约为０．０５ｎｍ的窄带滤光系统。     

Controlled synthesis of monodisperse silver nanocubes via a solvothermal method

Silver nanostructures have been synthesized via a simple solvothermal method by adding sodium sulfide (Na₂S) into the solution. The morphologies of products are controlled by the concentration of Ag₂S formed in the initial stage. A low-concentration Ag₂S (12.5 ~ 50 μM) acts as the catalysis, leading to the formation of silver nanocubes with controllable sizes. However, a high-concentration Ag₂S (100 μM) mainly acts as the controlling agent. It facilitates the synthesis of silver nanowires. Reaction conditions, the reaction temperature and the molar ratio of the repeating unit of PVP to AgNO₃ (R), have also been investigated. A possible mechanism is proposed to interpret the synthesis of silver nanocubes and nanowires. Finally, our results indicate that this strategy provides a simple route to prepare silver nanocubes with adjustable sizes.     

固体核径迹自动测量系统及其主要应用

图象分析技术在固体核径迹自动测量中有着重要的作用，特别是在径迹参数测量方面更具有显著特点，本文阐述了固体核径迹自动计数和参数测量的方法及其主要的应用领域。     

植物纤维与生物降解塑料界面相容性研究进展

分析了植物纤维/生物降解塑料界面的相容性及影响因素,从植物纤维表面改性处理和生物降解塑料改性处理两方面介绍了改善植物纤维与生物降解塑料界面相容性的方法,并展望了生物降解塑料的发展趋势。