基于发展科学探究能力的高中化学教学实践 ——以"元素周期律"章节为例

基于学生在学习元素周期律时存在的普遍问题改进了教学实践,分析了元素周期律发展学生科学探究能力的价值,设计了四个教学环节——趣味导入,成果展示;分析规律,做出猜想;设计方案,收集证据;梳理模型,迁移应用,并提出了三点针对学生探究能力发展的教学建议.     

Dual effect synergistically triggered Ce:(Y,Tb)3(Al,Mn)5O12 transparent ceramics enabling a high color-rendering index and excellent thermal stability for white LEDs

Ce:Y₃Al₅O₁₂ transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce³⁺ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)₃(Al,Mn)₅O₁₂ TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb³⁺ and Mn²⁺ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb³⁺ ion and the energy transfer between Ce³⁺ and Mn²⁺ ions were verified in prepared TCs.     

Toughness and R-curve behaviour of laminated Si3N4/SiCw ceramics

Laminated Si₃N₄/SiC_w ceramics were successfully prepared by tape casting and hot-pressing. Its mechanical properties were measured and the impact resistance was discussed. The toughness of the laminated Si₃N₄/SiC_w ceramics was 13.5 MPa m^1/2, which was almost 1.6 times that of Si₃N₄/SiC_w composite ceramics, namely 8.5 MPa m^1/2. Moreover, the indentation strength of laminated Si₃N₄/SiC_w ceramics was not sensitive to increasing indentation loads and exhibited a rising R-curve behaviour, indicating that the laminated Si₃N₄/SiC_w ceramics had excellent impact resistance. The improved toughness and impact resistance of laminated Si₃N₄/SiC_w ceramics was attributed to the residual stress caused by a thermal expansion coefficient mismatch between the different layers, resulting in crack deflection and bridging of SiC whiskers in the interface layer, thus consuming a large amount of fracture work.     

圆型限制性三体问题的动力学特征

禁行域在圆型限制性三体问题中对第三体的运动有极为重要的影响. 利用零速度曲线讨论天体禁行域与系统参数之间的关系. 禁行域与雅可比常数有关，且能影响天体的运动区域和轨道构型. 利用最大李雅普诺夫指数寻找该模型的混沌轨道，给出混沌轨道在不同系统参数下随天体初始位置的分布. 这些分布说明，当第三天体从两主天体连线的中点处释放时，容易产生混沌运动；当质量参量足够小时，体系无法产生混沌现象.     

HPLC法测定伐地昔布的有关物质

建立高效液相色谱法检测伐地昔布的有关物质.采用α-酸性糖蛋白键合硅胶的手性色谱柱,以乙腈-醋酸铵缓冲液(0.01 mol/L,pH4.0)作为流动相进行梯度洗脱,检测波长215 nm.伐地昔布与5个已知杂质均可达到基线分离,在各自浓度范围内线性关系良好,平均回收率95.13％～99.77％,RSD1.10％～1.77％,检测限0.017 9～0.060 1 μg/mL,定量限0.059 7～0.200 0 μg/mL.方法专属性强,准确度好,灵敏度高,可为伐地昔布的质量控制及后续分离提纯和帕瑞昔布的质量控制提供指导.     

建筑用气密膜相关强度性能试验研究

气密膜是被动房和超低能耗建筑气密性处理的常用材料,由于试验设备及方法等原因,国内对建筑用气密膜性能的试验研究较少,从施工应用角度出发,针对国内外无纺布基气密膜的相关强度性能开展试验研究,为气密膜的工程应用提供参考.     

一起发电机定子接地故障的分析与处理

文章介绍了海外某大型火力发电厂发生的一起发电机定子接地故障的分析和处理过程,对发电厂类似故障的处理和海外发电厂的运行和维护提供了参考。     

乘用车悬架静强度与疲劳载荷研究

为了快速获得平台悬架静强度与疲劳载荷,本文依据某A级平台5款量产车型试验场道路栽荷数据,以前麦弗逊悬架为研究对象,先对轮心载荷幅值进行统计分析,根据应力-强度干涉模型,得到该平台前悬架的强度载荷边界,及其与车辆满载轮荷的G载荷系数.再通过研究5款车型车轮轮心疲劳伪损伤与轮荷的关联关系,得到该平台悬架的疲劳栽荷.此方法可快速获得同平台悬架静强度与疲劳载荷,省去实车道路谱采集并提升了工作效率.     

Lithiophilic MXene-Guided Lithium Metal Nucleation and Growth Behavior

The positive effects of a lithiophilic substrate on the electrochemical performance of lithium metal anodes are confirmed in several reports, while the understanding of lithiophilic substrate-guided lithium metal nucleation and growth behavior is still insufficient. In this study, the effect of a lithiophilic surface on lithium metal nucleation and growth behaviors is investigated using a large-area Ti₃C₂T_x MXene substrate with a large number of oxygen and fluorine dual heteroatoms. The use of the MXene substrate results in a high lithium-ion concentration as well as the formation of uniform solid–electrolyte-interface (SEI) layers on the lithiophilic surface. The solid–solid interface (MXene-SEI layer) significantly affects the surface tension of the deposited lithium metal nuclei as well as the nucleation overpotential, resulting in the formation of uniformly dispersed lithium nanoparticles ( ≈ 10–20 nm in diameter) over the entire MXene surface. The primary lithium nanoparticles preferentially coalesce and agglomerate into larger secondary particles while retaining their primary particle shapes. Subsequently, they form close-packed structures, resulting in a dense metal layer composed of particle-by-particle microstructures. This distinctive lithium metal deposition behavior leads to highly reversible cycling performance with high Columbic efficiencies >  99.0% and long cycle lives of over 1000 cycles.