Ku波段编码式电控超薄周期单元设计与验证

编码式电控周期单元通过加载电子控制器件使周期结构具有编码式的电可调特点. 本文利用PIN二极管, 设计实现了一种工作在Ku波段的超薄平面电控单元结构. 当外加电压控制二极管导通或截止时, 该结构的反射相位呈现出180°的相位差, 并且具有较低的反射损耗. 因此, 当对周期排列的单元外加不同的电压时, 可等效为用不同组合的“1”, “0”对结构进行编码, 从而可以获得不同的电磁功能. 为验证单元的编码特性, 从“场”与“路”两个角度考虑, 设计了实际的偏置电路, 制作了单元样品, 并基于波导法测试了其性能. 实验结果表明: 在加载不同的控制电压时, 制作的单元结构实现了设计的低损耗和相位差; 实验与仿真符合良好. 提出的周期单元形式简单, 厚度超薄, 其电控编码式特性在主动式隐身表面或波束捷变天线设计等许多方面都有潜在应用.     

Efficient Solar-osmotic Power Generation from Bioinspired Anti-fouling 2D WS2 Composite Membranes

Nanofluidic reverse electrodialysis provides an attractive way to harvest osmotic energy. However, most attention was paid to monotonous membrane structure optimization to promote selective ion transport, while the role of external fields and relevant mechanisms are rarely explored. Here, we demonstrate a Kevlar-toughened tungsten disulfide (WS₂) composite membrane with bioinspired serosa-mimetic structures as an efficient osmotic energy generator coupling light. As a result, the output power could be up to 16.43 W m⁻² under irradiation, outperforming traditional two-dimensional (2D) membranes. Both the experiment and simulation uncover that the generated photothermal and photoelectronic effects could synergistically promote the confined ion transport process. In addition, this membrane also possesses great anti-fouling properties, endowing its practical application. This work paves new avenues for sustainable power generation by coupling solar energy.     

Dynamic scaling and optical properties of Zn（S,O, OH） thin film grown by chemical bath deposition

The scaling behavior and optical properties of Zn(S, O and OH) thin films deposited on soda-lime glass substrates by chemical bath deposition method were studied by combined roughness measurements, scanning electron microscopy and optical properties measurement. From the scaling behaviour, the value of growth scaling exponent β , 0.38±0.06, was determined. This value indicated that the Zn(S, O, OH) film growth in the heterogeneous process was influenced by the surface diffusion and shadowing effect. Results of the optical properties measurements disclosed that the transmittance of the film was in the region of 70%-88% and the optical properties of the film grown for 40 min were better than those grown under other conditions. The energy band gap of the film deposited with 40 min was around 3.63 eV.     

一种兼有高增益和宽带低散射特征的波导缝隙天线设计

设计了一种同时具备高增益和宽带低散射特征的波导缝隙天线.将蚀刻有互补开口谐振环的方形贴片人工磁导体正交布阵得到宽带低雷达截面积(RCS)反射屏并以之代替原天线的全金属反射板,通过优化反射屏的加载方式,在展宽天线工作频带、提高天线增益的同时,实现了宽频域范围内天线鼻锥方向RCS减缩.实测结果表明:加载低RCS反射屏的缝隙天线工作带宽增加了100 MHz,前向增益提高了3.2 dB,在5.52—6.63GHz范围内RCS减缩量达10 dB以上,减缩带宽达到20%.     

Tm3+掺杂的NaYF4微米颗粒中强烈的单带下转换荧光发射

采用柠檬酸钠辅助的水热方法合成了一系列具有不同长径比的Tm³⁺掺杂的β-NaYF₄ (NaYF:Tm³⁺)微米棒(盘).通过X射线衍射(XRD),扫描电子显微镜(SEM),能量色散X射线荧光光谱(EDX),傅里叶变换红外(FTIR)光谱和激光光谱学等手段对所制备的系列β-NaYF₄微米棒(盘)进行了表征. XRD和SEM分析表明β-NaYF₄微米棒(盘)的长径比依赖于前驱液的pH值,随着前驱液的pH值的增加,从长棒逐渐过渡到六角盘.光谱测量结果表明:一系列NaYF₄:Tm³⁺微米晶体在656 nm脉冲激光选择激发下,均获得了强烈的单带近红外下转换荧光发射.系统研究了激发波长、环境温度和颗粒长径比对NaYF₄:Tm³⁺微米晶体中单带近红外荧光强度的调控.结果表明:颗粒长径比越大,荧光强度越强.进一步探索了颗粒长径比调控的荧光增强机理,并提出了基于长径比控制的缺陷空位机理.     

一种宽带可重构反射型极化旋转表面

将超材料设计思想与微电机系统（micro-electro-mechanical system,MEMS）技术相结合,提出了一种宽带可重构反射型极化旋转表面.该结构由上层方形金属贴片、中间介质层、金属底板以及连接贴片与底板的金属通孔构成,通过在电流短路点处加载MEMS开关,使其具有电可调特性.仿真结果表明,当MEMS开关导通时,该结构能在7.78 GHz–14.10 GHz频带内将入射的线极化波转化为正交极化波并反射;当MEMS开关断开时,入射波则以同极化全反射.加工了实际的样品并进行了测试,结果与仿真符合较好.该结构具有结构简单易加工、器件个数少、工作频带宽、损耗低等优点,在电磁波动态调控中具有潜在应用价值.     

Yb浓度对功率依赖的上转换荧光色彩的敏感度调控

控制激发光功率密度是一种调控红绿荧光比率的简单方法.然而,大多数上转换系统对功率的调控并不敏感.本文通过柠檬酸钠辅助的水热法,合成了一系列具有不同Yb浓度掺杂的NaYF₄：Yb/Ho微米棒.通过激光共聚焦显微镜系统,研究了Yb浓度和激发功率密度依赖的NaYF₄：Yb/Ho微米棒的上转换荧光特性.发射谱和同步荧光成像图案表明：荧光红绿比率不仅敏感于激发功率,而且敏感度依赖于Yb浓度.随着Yb浓度的增加,功率调控的红绿比率的敏感度增加,这暗示了功率调控的红绿比率的敏感度可以作为一种度量和评估Yb掺杂浓度的有效途径和方法.通过上/下转换发射谱、激发谱和功率依赖关系,揭示了功率调控红绿比率的机理,并提出了荧光色彩敏感于功率调控的上转换系统具有的特征和判据.本研究为设计和合成高敏感度的功率调控的上转换材料提供了理论基础和实验数据.     

General steady-state solutions for transversely isotropic thermoporoelastic media in three dimensions and its application

This paper presents a set of 3D general solutions for thermoporoelastic media for the steady-state problem. By introducing two displacement functions, the equations governing the elastic, pressure and temperature fields are simplified. The operator theory and superposition principle are then employed to express all the physical quantities in terms of two functions, one of which satisfies a quasi–Laplace equation and the other satisfies a differential equation of the eighth order. The generalized Almansi's theorem is used to derive the displacements, pressure and temperature in terms of five quasi-harmonic functions for various cases of material characteristic roots. To show its practical significance, an infinite medium containing a penny-shaped crack subjected to mechanical, pressure and temperature loads on the crack surface is given as an example. A potential theory method is employed to solve the problem. One integro-differential equation and two integral equations are derived, which bear the same structures to those reported in literature. For a penny-shaped crack subjected to uniformly distributed loads, exact and complete solutions in terms of elementary functions are obtained, which can serve as a benchmark for various kinds of numerical codes and approximate solutions.     

竖直矩形通道内液体流动

通过对沸腾气泡在液体中的受力分析,建立了沸腾气泡长大过程的动力学方程;进而获得了沸腾气泡的生长速率与脱离直径的计算方法.采用图象捕集与处理系统,对竖直矩形通道内液体流动沸腾气泡长大与脱离行为进行实验测定,结合模型求解,获得了气泡生长速率、气泡脱离直径、气泡与加热壁面的接触角等参数随操作条件的变化;由模型计算所得的气泡脱离直径与实测值较为符合.     

超疏水表面微纳二级结构对冷凝液滴最终状态的影响

从超疏水表面(SHS)上初始冷凝液核长大、合并、形成初始液斑开始,分析计算了冷凝液斑变形成为Wenzel或Cassie液滴过程中界面能量的变化,并以界面能曲线降低、是否取最小值为判据,确定冷凝液滴的最终稳定状态.计算结果表明:在只有微米尺度的粗糙结构表面上,冷凝液滴的界面能曲线一般都是先降低再升高,呈现Wenzel状态;而当表面具有微纳米二级粗糙结构,且纳米结构的表面空气面积分率较高时,冷凝液滴的能量曲线持续降低,直至界面能最小的Cassie状态,因此可以自发地形成Cassie液滴.还计算了文献中具有不同结构参数的SHS上冷凝液滴的状态和接触角,并与实验结果进行了比较,结果表明,计算的冷凝液滴状态与实验观察结果完全吻合.因此,微纳二级结构是保持冷凝液滴在SHS上呈现Cassie状态的重要因素.