一类二阶延迟微分方程梯形方法的延迟依赖稳定性分析

本文涉及一类二阶延迟微分方程数值方法的稳定性研究．通过运用边界轨迹法,分析了梯形方法的延迟依赖稳定区域并找到其准确边界．随后建立了解析和数值稳定区域的联系并从理论上证明了梯形方法能完全保持模型问题的延迟依赖稳定性．     

压水堆核电厂余热排出系统的可靠性建模与分析

为提高压水堆余热排出系统(RHRS)可靠性,对RHRS的定期检修与维护提供指导与参考,本研究采用故障树对RHRS进行可靠性建模,对系统部件进行重要度指标评价。基于重要度指标评价结果提出了含公用备件的冷备系统的改进方案,引入动态故障树冷备门描述其失效模式,利用Markov模型进行定量分析。研究结果表明,优化后的RHRS可靠度有明显提升。     

Thermal decomposition of 1-hexene by flash pyrolysis: A study of initial decomposition mechanism

Thermal decomposition of 1-hexene at temperatures 295-1410 K was conducted using a flash pyrolysis micro-reactor coupled to laser-based vacuum ultraviolet photoionization time-of-flight mass spectrometer (VUV-PI-TOFMS). The decomposition mechanism of 1-hexene was developed with the help of theoretical calculation performed at the MRCI/cc-pvtz//CASSCF/6–31+G(d,p) level. The γ-scission and diradical retro-ene reactions were determined as the main initial decomposition reactions in the temperature range 990-1240 K. Two diradical retro-ene reaction channels, 1,5-diradical and 1,6-diradical reactions, were proposed in order to interpret the appearance of the C₄H₈ species. The 1,5-diradical retro-ene reaction involved a 1,5-diradical intermediate that subsequently decomposed via CC β-scissions to the C2, C3 and C4 products. The 1,6-diradical retro-ene reaction proceeded via a 1,6-diradical intermediate and CC β-scissions to produce the C2 and C4 species. The proposed diradical retro-ene mechanism was evidenced indirectly by the early product distribution of 1-hexene pyrolysis in a flow reactor at 1173 K determined by synchrotron radiation VUV-PI-TOFMS. It was verified in the flash pyrolysis of 1-heptene as well.     

大孔吸附树脂分离纯化异甘草素的研究

研究大孔吸附树脂分离纯化异甘草素的工艺条件及参数。通过研究HPD-600、D4020、D101、AB-8、NKA-II、AL-2和NKA-9树脂对异甘草素的吸附和解吸附能力,筛选最佳树脂为AB-8,并研究了其对异甘草素的吸附和解吸附性能,确定了最佳的吸附与解吸附工艺参数,吸附:pH=5,室温,流速1.5BV/h,溶液处理量为5BV;脱附:洗脱剂为70%的乙醇溶液,流速1BV/h,洗脱剂用量4.5BV。异甘草素样品溶液经AB-8树脂吸附与脱附后回收率为76.7%,纯度由2.02%提高到29.1%,提高了14.4倍。实验结果表明,AB-8树脂对异甘草素的吸附量大,脱附容易,可以应用于异甘草素的分离纯化。     

Synthesis of spiro[4.4]nonane-1,6-diols via the hydrogenation of spiro[4.4]nonane-1,6-dione: the profound effect of hydrogenating agents

The synthesis of spiro[4.4]nonane-1,6-diols via the catalytic as well as stoichiometric hydrogenation of spiro[4.4]nonane-1,6-dione was studied. Profound effects of the hydrogenation catalysts and reagents on the stereoselectivity of the products were observed. The choice of solvent also was found to have a significant influence on the product selectivity. The opening of a spiro-ring in the starting material was identified as a major side reaction in alcohol solvents. The absolute configuration of the trans, trans-diol was unambiguously determined by X-ray crystallography.     

聚三甲硅基丙炔的表面氟化改性及氧氮透过性

对聚三甲硅基丙炔（ＰＴＭＳＰ）进行表面氟化改性，改性膜的氧氮选择性提高，气体透过稳定性增加．用ＸＰＳ谱分析改性后的膜表面，其表面结构发生了显著变化。     

制备参数对ZrO2气凝胶超细粉织构和结构性质的影响 Ⅰ.水凝胶pH值

用超临界流体干燥（ＳＣＦＤ）法制备出大孔高比表面ＺｒＯ２气凝胶超细粉，详细考察了初始水凝胶ｐＨ值对ＺｒＯ２超细粉形貌、晶相组成、颗粒大小与分布、比表面积及孔结构等织构和结构性质的影响。在实验范围内，当水凝胶ｐＨ值为１０．３０时，所制得的ＺｒＯ２超细粉具有最大的比表面积和孔体积，最小的表观堆密度和平均粒径，颗粒分布均匀狭窄，颗粒间连接成三维网络构状态，较好地保持了凝胶原始织构。     

Fingerprint analysis and quality consistency evaluation of flavonoid compounds for fermented Guava leaf by combining high‐performance liquid chromatography time‐of‐flight electrospray ionization mass spectrometry and chemometric methods

Guava leaves are used in traditional herbal teas as antidiabetic therapies. Flavonoids are the main active of Guava leaves and have many physiological functions. However, the flavonoid compositions and activities of Guava leaves could change due to microbial fermentation. A high‐performance liquid chromatography time‐of‐flight electrospray ionization mass spectrometry method was applied to identify the varieties of the flavonoids in Guava leaves before and after fermentation. High‐performance liquid chromatography, hierarchical cluster analysis and principal component analysis were used to quantitatively determine the changes in flavonoid compositions and evaluate the consistency and quality of Guava leaves. Monascus anka Saccharomyces cerevisiae fermented Guava leaves contained 2.32‐ and 4.06‐fold more total flavonoids and quercetin, respectively, than natural Guava leaves. The flavonoid compounds of the natural Guava leaves had similarities ranging from 0.837 to 0.927. The flavonoid compounds from the Monascus anka S. cerevisiae fermented Guava leaves had similarities higher than 0.993. This indicated that the quality consistency of the fermented Guava leaves was better than that of the natural Guava leaves. High‐performance liquid chromatography fingerprinting and chemometric analysis are promising methods for evaluating the degree of fermentation of Guava leaves based on quality consistency, which could be used in assessing flavonoid compounds for the production of fermented Guava leaves.     

Managing Secondary Phase Lead Iodide in Hybrid Perovskites via Surface Reconstruction for High-Performance Perovskite Solar Cells with Robust Environmental Stability

Rationally managing the secondary-phase excess lead iodide (PbI₂) in hybrid perovskite is of significance for pursuing high performance perovskite solar cells (PSCs), while the challenge remains on its conversion to a homogeneous layer that is robust stable against environmental stimuli. We herein demonstrate an effective strategy of surface reconstruction that converts the excess PbI₂ into a gradient lead sulfate-silica bi-layer, which substantially stabilizes the perovskite film and reduces interfacial charge transfer barrier in the PSCs device. The perovskite films with such bi-layer could bear harsh conditions such as soaking in water, light illumination at 70 % relative humidity, and the damp-thermal (85 °C and 30 % humidity) environment. The resulted PSCs deliver a champion efficiency up to 24.09 %, as well as remarkable environmental stability, e.g., retaining 78 % of their initial efficiency after 5500 h of shelf storage, and 82 % after 1000 h of operational stability testing.