基于STSE教育理念探秘苹果中的化学知识

《普通高中化学课程标准（2017年版）》强调STSE教育理念。通过对苹果中铁元素、氧气、多酚氧化酶活性对苹果褐变现象影响的实验探究，为提高苹果的使用价值以及食品保鲜技术提供了理论基础，让学习者在"苹果"中感受化学知识的生活化及科学知识的价值。     

低压驱动高阻值层液晶透镜

针对传统电极驱动液晶透镜的电场分布在驱动电极边缘的问题,设计了一种高阻值层驱动电极来控制液晶分子偏转的低压驱动和焦距可调的液晶透镜.利用磁控溅射工艺在含镂空孔阵列的面状铝电极基板表面沉积一层掺铝氧化锌透明薄膜,形成高阻值层驱动电极;利用液晶盒成盒工艺将制备好的驱动电极基板和公共电极基板(氧化铟锡玻璃基板)组装成液晶透镜,研究掺铝氧化锌高阻值层、驱动电压、工作频率对液晶透镜光学性能的影响.实验结果表明,对比传统电极驱动液晶透镜,高阻值层电极驱动液晶透镜在驱动电压2.2Vrms和工作频率130kHz下获得的干涉圆环均匀,聚焦光斑小.同时,在驱动电压1.8～2.8Vrms和工作频率130kHz下所制备的液晶透镜焦距可调范围为4.27～2.88mm.     

胎儿脐带血铅水平与钙、锌、铁的关系研究

目的研究胎儿脐带血中的铅与钙、锌、铁的含量以及两两之间的相关性。方法采用原子吸收光谱法对398例脐带血铅和钙、锌、铁的含量进行测定,并对它们进行相关性分析。结果 398例脐带血铅和钙、锌、铁的质量浓度分别为铅(37.96±17.78)μg/L、钙(1.51±0.29)mmol/L、锌(30.01±11.14)μmol/L、铁(8.63±1.39)mmol/L。线性回归分析显示:铅与钙(r=-0.563,P0.01)、铅与锌(r=-0.424,P0.01)有相关性,铅与铁无显著相关(r=0.018,P0.05)。结论随着胎儿体内血铅水平的上升,二价元素钙、锌含量有下降趋势,即中毒元素铅会干扰胎儿体内的必需二价元素的代谢。     

镨铁硼低温波荡器机械结构的传热分析

对镨铁硼材料在低温和室温下的热学和力学物性进行了测量;使用实测的镨铁硼物性并结合数值模拟的方法对镨铁硼低温波荡器的传热特性进行了分析;结果表明,磁极和磁极夹持机构与磁铁间的热传导是冷却磁铁的关键因素,冷却管道宜采用双通道同向并联的方式。使用该设计通过液氮可以冷却磁铁至82K,同时能够控制由于温差带来的磁极间相位误差小于0.1度,满足镨铁硼低温波荡器设计要求。     

氟离子选择电极测定黄磷尾气中气态氟含量

采用NaOH溶液吸收黄磷尾气中气态氟,氟离子选择电极测定其氟含量。结果表明,电极电位与5~100.0μg/mL氟离子浓度的对数有良好的线性关系(R=0.99992)。相对标准偏差(RSD)为3.05%,平均回收率为98.70%~99.69%。该方法操作简便、干扰小、准确度高,分析成本低,适用于黄磷尾气中氟含量的测定。     

德国科学家发明新型核工程防辐射屏蔽材料

德国慕尼黑技术大学海因茨.迈尔-莱布尼茨试验中子源(又称慕尼黑实验反应堆2号FRMⅡ)的研究人员发明一种可回收利用的新型防辐射屏蔽材料。这种材料是一种粉末,含有铁颗粒、石蜡油     

Alternating-current losses in two-layer superconducting cables consisting of second-generation superconductors coated by U-shaped ferromagnetic materials

Alternating-current losses in a two-layer superconducting cable, each layer being composed of 15 closely-spaced rectangular wires made up of second-generation superconductors when the ends of wires are coated by either a non-magnetic or strong ferromagnetic material having a U profile is numerically investigated. Computations are carried out through the finite-element method. The alternating-current losses do not increase significantly if the relative permeability of the coating is increased three orders of magnitude, provided that the current amplitude is less than half of the critical current in a superconducting wire. However, the losses are much higher for ferromagnetic coating if the amplitude of the applied current oscillating at 50 Hz is close to the critical current. The ferromagnetic coating is seen to accumulate the magnetic field lines normally on its surfaces, while the field lines are parallel to the long axes of the wires, leading to more significant flux penetration in the coated regions. This facilitates a uniform low-loss current flow in the uncoated regions of the wires. In contrast, coating with a non-magnetic material gives rise to a considerably smaller current flow in the uncoated regions, whereas the low-loss flow is maintained in the coated regions. Moreover, the current flows in opposite directions in the coated and uncoated regions, where the direction in each region is converse for the two materials.