A Sensing and Stretchable Polymer-Dispersed Liquid Crystal Device Based on Spiderweb-Inspired Silver Nanowires-Micromesh Transparent Electrode

Polymer-dispersed liquid crystal (PDLC) devices are truly promising optical modulators for information display, smart window as well as intelligent photoelectronic applications due to their fast switching, large optical modulation as well as cost-effectiveness. However, realizing highly soft PDLC devices with sensing function remains a grand challenge because of the intrinsic brittleness of traditional transparent conductive electrodes. Here, inspired by spiderweb configuration, a novel type of silver nanowires (AgNWs) micromesh-based stretchable transparent conductive electrodes (STCEs) is developed to support the realization of soft PDLC device. Benefiting from the embedding design of AgNWs micromesh in polydimethylsiloxane (PDMS), the STCEs can maintain excellent electrical conductivity and transparency even in various extreme conditions such as bending, folding, twisting, stretching as well as multiple chemical corrosion. Further, STCEs with the embedded AgNWs micromesh endow the assembled PDLC device with excellent photoelectrical properties including rapid switching speed (<1 s), large optical modulation (69% at 600 nm), as well as robust mechanical stability (bending over 1000 cycles and stretching to 40%). Moreover, the device displays the pressure sensing function with high sensitivity in response to pressure stimulus. It is conceivable that AgNWs micromesh transparent electrodes will shape the next generation of related soft smart electronics.     

一种无延时单相并网变换器dq电流解耦控制方法

以单相脉宽调制(pulse width modulation,PWM)变换器作为研究对象,以改善电流控制器的动态性能为目的,提出一种无延时控制方法。单相变换器传统矢量控制方法需要虚构正交电流分量,但传统正交信号发生器(orthogonal signal generator,OSG)在虚构出与单相电网电流正交的物理量时存在一定的延时,从而会恶化电流控制器的动态性能。针对虚构电流引起的延时问题,提出了一种无延时单相并网变换器电流控制方法。首先,建立了单相PWM变换器在dq旋转坐标系下的数学模型。其次,针对矢量控制在单相系统无法直接实现的问题,介绍了几种传统的OSG算法的原理。然后,提出一种无延时正交电流虚构算法,并给出了无延时正交电流虚构算法实现框图。最后,对所提的算法与传统的OSG算法进行仿真和实验对比分析,仿真和实验结果均验证了所提算法的有效性和可行性。     

谐振器加载石墨烯的双通带可调滤波衰减器设计

石墨烯材料在微波段的阻抗可控特性是其最有价值的应用特性之一。文中首次分析了石墨烯对微带 多模谐振的影响机理,提出了一种集成滤波衰减功能为一体的灵活可控器件。首先,对不同位置加载石墨烯的微带双 模谐振器进行了严格的等效电路建模,通过奇偶模分析法及输入导纳参数计算,探究了双模谐振受石墨烯阻抗及其加 载位置的影响,明晰了石墨烯材料对微波谐振器的影响。随后设计了动态可调的滤波衰减器并阐述了石墨烯材料在谐 波控制上的潜在应用点。最后,采用不同尺寸的双模谐振器进行石墨烯加载并完成双通带幅度独立可控的滤波衰减器 的设计,仿真与实测结果吻合良好,验证了阻抗可控石墨烯材料在可调微波衰减类器件上的应用前景。     

(CoFe)Se2@NC超级电容器电极材料的制备及其电化学性能

金属-有机框架(MOF)衍生的过渡金属硒化物和多孔碳纳米复合材料具有巨大的储能优势,是应用于电化学储能的优良电极材料。采用共沉淀法制备CoFe类普鲁士蓝(CoFe-PBA)纳米立方,并通过静电组装在CoFe-PBA上包覆聚吡咯(PPy)得到CoFe-PBA@PPy;通过在400℃氮气中退火并硒化成功制备了氮掺杂的碳(NC)包覆(CoFe)Se₂的(CoFe)Se₂@NC纳米复合材料,并对其结构和形貌进行了表征。以(CoFe)Se₂@NC为电极制备了超级电容器,测试了其电化学性能,结果表明,在电流密度1 A/g时超级电容器的比电容达到1047.9 F/g,在电流密度5 A/g下1000次循环后具有良好的循环稳定性和96.55%的比电容保持率。由于其性能优越、无毒、成本低和易于制备,未来(CoFe)Se₂@NC纳米复合材料在超级电容器中具有非常大的应用潜力。     

DAM两相闭式热虹吸回路冷却系统实验研究

两相热虹吸回路由于较高的散热性能在高功率电子设备冷却领域有较好的应用前景。为了解决四通道数字阵列模块的冷却问题,本文设计了一套两相闭式热虹吸回路冷却系统样机并对系统启动特性、充液量和工作倾角对系统散热性能的影响进行了实验研究。研究结果表明,样机系统结构及散热性能满足指标要求,启动性能和工作性能良好。此外,该系统对热耗1600 W、局部热流密度接近100 W/cm~2的组件的冷却效果良好。     

Na_2EDTA滴定法测量水质总硬度的不确定度评定

以实验室水质总硬度样2017HB800001为例,对Na2EDTA滴定法测定水质总硬度的不确定度的来源进行评定,通过分析氧化锌标准溶液的配制,Na2EDTA标准溶液的标定,水样实际消耗Na_2EDTA标准溶液的滴定体积,水样吸取的体积及重复性的测量等因素进行总硬度测量的不确定度的评定,取包含因子k=2,则扩展不确定度:U=1.50及测定结果为:C=(270.87±1.50)mg/L,由此分析得出此水样产生不确定度的主要来源是样品溶液的测定和Na2EDTA标准溶液的标定。     

蛋白质与淀粉的相互作用对陈化大米质构特性的影响

以１０种大米为材料研究了在４０℃条件下储藏６个月后蒸煮大米粘度和硬度的变化以及蛋白质的溶解性、蛋白与淀粉相互作用的变化。结果表明,陈化以后蒸煮大米的硬度上升,粘度下降。蛋白质总量基本不变,但是,总蛋白以及清蛋白、球蛋白、醇溶蛋白和谷蛋白的提取率都降低。ＳＤＳ－ＰＡＧＥ电泳图谱显示清蛋白、球蛋白和谷蛋白的高分子量亚基含量增多,低分子量亚基含量减少,非淀粉粒蛋白与淀粉的相互作用在大米陈化过程中增加。通过对６０ＫＤ淀粉粒蛋白含量高的４种大米的研究表明,大米陈化过程中淀粉粒蛋白与淀粉的相互作用增加,这种变化与蒸煮大米粘度变化的相关性显著（ｐ＝００５）,因此,淀粉粒蛋白与淀粉相互作用增加可能是导致陈化大米蒸煮后粘度降低的一个重要原因。     

Density functional theory studies on the structures and electronic communication of meso-ferrocenylporphyrins: long range orbital coupling via porphyrin core

The molecular and electronic structures together with the electronic absorption spectra of a series of metal free meso-ferrocenylporphyrins, namely 5-ferrocenylporphyrin (1), 5,10-diferrocenylporphyrin (2), 5,15-diferrocenylporphyrin (3), 5,10,15-triferrocenylporphyrin (4), and 5,10,15,20-tetraferrocenylporphyrin (5) have been studied with the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. For the purpose of comparative studies, metal free porphyrin without any ferrocenyl group (0) and isolated ferrocene (6) were also calculated. The effects of the number and position of meso-attached ferrocenyl substituents on their molecular and electronic structures, atomic charges, molecular orbitals, and electronic absorption spectra of 1-5 were systematically investigated. The orbital coupling is investigated in detail, explaining well the long range coupling of ferrocenyl substituents connected via porphyrin core and the systematic change in the electronic absorption spectra of porphyrin compounds.