Synthesis, Crystal Structure, and Physical Properties of the Perovskite Iridates

Perovskite iridates have emerged as a new paradigm for studying the strongly correlated electron physics with strong spin-orbit coupling. The “113” alkaline-earth iridates AIrO3 (A = Ca, Sr, Ba) display a rich variety of crystallographic and electronic states and are now attracting growing research interest. This chapter aims to provide an overview for these “113” iridates, including the materials’ synthesis, crystal structure, major physical properties, and other interesting results such as the effects of pressure and chemical substitutions, as well as theoretical perspectives

Stator re-stagger optimization in multistage axial compressor

As a widely applied technique in multistage axial compressors, variable stator vanes (VSV) can flexibly rematch the blade rows to fulfil a variety of aerodynamic performance requirements, such as high efficiency and wide surge margin. The purpose of this paper is to develop an optimization method to quickly determine VSV settings during the preliminary design phase. A mean-line method with a model calibration procedure is adopted to evaluate compressor performance, and the NSGA-II algorithm is employed for automatic optimization. The developed optimization system is then employed to determined re-stagger arrangement in a multistage compressor. A single-speed optimization with performance constraints of specific operating point and a multi-speed optimization with different control laws are conducted. Results are compared with available experimental re-stagger scheme, which verifies the effectiveness of the restagger optimization method. Moreover, method is proposed to determine operating parameters of a working point with a user-defined pressure ratio or mass flow rate after variable geometry

Pressure tuning of optical reflectivity in LuH2

Recently, the claim of room-temperature superconductivity in nitrogen-doped lutetium hydride at near-ambient conditions has attracted tremendous attention. Criticism of the work rises shortly, while further explorations are needed to settle the dispute. One of the intriguing observations is the pressured-induced color change, which has been reproduced in the lutetium dihydride LuH2 while its mechanism remains unclear. Through optical reflectivity measurements of LuH2 in the visible to near-infrared region, we observe strong light absorption next to the sharp plasmon resonance, which continuously shifts to higher energies with increasing pressure. It gives rise to the increased reflection of red light and suppressed reflection of blue light. Our work sheds light on resolving the puzzles regarding the pressure induced color change in LuH2.Comment: 8 pages, 6 figure