Quantum dots (QDs), ac lass of promising candidates for harvesting visible light, generally exhibit low activity and selectivity towards photocatalytic CO 2 reduction. Functionalizing QDs with metal complexes (or metal cations through ligands) is aw idely used strategy for improving their catalytic activity;h owever,t he resulting systems still suffer from lowselectivity and stability in CO 2 reduction. Herein, we report that doping CdS QDs with transition-metal sites can overcome these limitations and provideasystem that enables highly selective photocatalytic reactions of CO 2 with H 2 O (100 %s electivity to CO and CH 4 ), with excellent durability over 60 h. Doping Ni sites into the CdS lattice leads to effective trapping of photoexcited electrons at surface catalytic sites and substantial suppression of H 2 evolution. The method reported here can be extended to various transition-metal sites,a nd offers new opportunities for exploring QD-based earth-abundant photocatalysts.

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DC microgrids consist of multiple power electronic converter units interconnected in a network with sources and loads. They arise naturally in the power systems of electric ships, aircrafts, etc. The main focus of this work is to study the stability of power converters based dc microgrids. These high switching frequency electronics are controlled in a way as to maintain constant voltage, current, or power to the load. Due to their high bandwidth, they can be simplified as a constant power load. For this reason, a nonlinear system arises where it is no longer satisfactory to assume local stability. Methods presented in literature will be reviewed and a method based on Semidefinite Programming (SDP) will be used to simplify the analysis and stability study of these dc microgrids. Furthermore, a robust controller formulation based on a similar SDP is proposed in order to guarantee and expand the stability region using energy storage.978-1-4799-6735-3/15/$31.00 ©2015 IEEE

Ni-doped germanium clusters have been systematically investigated by using the density functional approach. The growth-pattern behaviors, stabilities, charge transfer, and polarities of these clusters are discussed in detail. Obviously different growth patterns appear between small-sized Ni-doped germanium clusters and middle- or larger-sized Ni-doped germanium clusters. The Ni-convex or substituted Ge(n) frames for small-sized clusters as well as Ni-concaved or encapsulated Ge(n) frames for middle- or large-sized clusters are dominant growth patterns. The calculated fragmentation energies manifest that the magic numbers of stabilities are 5, 8, 10, and 13 for Ni-doped germanium clusters; the obtained relative stabilities exhibit that the Ni-encapsulated Ge(10) cluster is the most stable species of all different-sized clusters, which is in good agreement with available experimental observations of CoGe(10)(-). Natural population analysis shows that different charge-transfer phenomena depend on the sizes of the Ni-doped Ge(n) clusters. Additionally, the properties of frontier orbitals and the polarities of Ni-doped Ge(n) clusters are also discussed.