摘要：近年来,基于磁共振和近场耦合的非辐射无线能量传输技术已被广泛应用.然而,由于传输效率和功率随着距离增加而大幅降低,基于双谐振器的无线能量传输系统仅适用于中短距离应用.基于多中继谐振器的无线能量传输系统可克服该问题,然而该复杂系统对微扰和缺陷极为敏感.针对上述问题,本文实验验证了稳健性拓扑无线能量传输.电磁能量可通过位于一维无线电波拓扑绝缘体两端的拓扑边界态之间的近场耦合高效传递.该结构可等效为具有复边界电势的宇称-时间对称的Su-Schrieffer-Heeger链.此外,所设计的线圈结构可抑制不相邻线圈之间非必要的交叉耦合.该工作理论和实验上验证了即使存在微扰的情况下,该系统仍可在拓扑边界态的奇异点附近保持极高的能量传输效率.该工作将拓扑电磁材料、非厄米物理和无线能量传输技术三者结合,为未来电子、交通运输和工业中的长距离无线传输提供稳定、高效的平台.

摘要：二维范德华材料被广泛用作光分解水催化剂,但其直接的能量转化效率有待提高.因此,寻找具有高效光解水催化特性的二维材料成为理论和实验研究的热点.本文从量子力学第一性原理出发,预言了一类具有高效光解水特性的光催化剂:二维Ⅲ族硫化物Janus多层结构InGaXY,M2XY和InGaX2(M=In/Ga;X,Y=S/Se/Te).理论计算表明,多层材料的内建电场不仅可以促进光生载流子的空间分离,而且可以有效地调控材料能带的位置,提高能量转化效率.Janus多层材料能量转化效率的理论上限可以达到38.5%,接近了理论极限值(47%).更重要的是,在InGaSSe双层引入Ga空位可以有效降低析氢和析氧反应的过电势,仅仅依靠光生载流子提供的电压就可以驱动光解水催化反应.该理论结果不仅预言了二维Ⅲ族硫化物Janus多层材料可以作为高效的光解水催化材料,而且为设计和寻找高效光催化材料提供了新思路.

摘要：The DC-DC converters are widely used in photovoltaic generating systems as an interface between PV module and the load. These converters must be chosen to be able to match the maximum power point (MPP) of PV module when climatic conditions change with different resistive load values. So DC-DC converters must be used with MPPT controller in order to reduce losses in the global PV system. This article focuses on the effect of climatic conditions on design of two components (inductance, capacitance) for three topologies of DC-DC converters commonly used in PV systems. When climatic conditions change, the boundary of inductance and capacitance parameters of DC-DC converter will change. These two parameters must be properly sized to achieve optimal efficiency for each converter. The design optimization is based on two principles: 1) for a steady-state operation in a continuous conduction mode, the inductance value for all choppers must be greater than the maximum value of boundary inductance, and 2) in order to limit the output voltage ripple of DC-DC converter below a desired value, the filter capacitance must be larger than the maximum value of boundary capacitance.