In this study a total of 186 complex halide systems were collected; the formabilities of ABX3 (X = F, Cl, Br and I) halide perovskites were investigated using the empirical structure map, which was constructed by Goldschmidt's tolerance factor and the octahedral factor. A model for halide perovskite formability was built up. In this model obtained, for all 186 complex halides systems, only one system (CsF-MnF2) without perovskite structure and six systems (RbF-PbF2, CsF-BeF2, KCl-FeCl2, TlI-MnI2, RbI-SnI2, TlI-PbI2) with perovskite structure were wrongly classified, so its predicting accuracy reaches 96%. It is also indicated that both the tolerance factor and the octahedral factor are a necessary but not sufficient condition for ABX3 halide perovskite formability, and a lowest limit of the octahedral factor exists for halide perovskite formation. This result is consistent with our previous report for ABO3 oxide perovskite, and may be helpful to design novel halide materials with the perovskite structure.

This paper reports the localized electrical, polarization reversal, and piezoelectric properties of the individual hexagonal ZnO nanorods, which are grown via the hydrothermal method and textured with [0001] orientation. The studies are conducted with conductive atomic force microscopy (c-AFM) and piezoresponse force microscopy (PFM) techniques. The correlation between the resistance switching and polarization reversal is discussed. The c-AFM results show that there is less variation on the set or reset voltage in nanorod samples, compared to that of the ZnO thin film. With increasing aspect ratio of the nanorods, both set and reset voltages are decreased. The nanorods with low aspect ratio show unipolar resistance switching, whereas both unipolar and bipolar resistance switching are observed when the aspect ratio is larger than 0.26. The PFM results further show the ferroelectric-like property in the nanorods. Comparing with that of the ZnO thin film, the enhanced piezoresponse in the nanorods can be attributed to the size effect. In addition, the piezoresponse force spectroscopy (PFS) experiments are conducted in ambient air, synthetic air, and argon gas. It shows that the depolarization field in the nanorod may be due to the moisture in the environment; moreover, the increased piezoresponse may relate to the absence of oxygen in the environment. It is also shown that the piezoelectric responses increase nonlinearly with the aspect ratio of the nanorods. By comparing the piezoresponse hysteresis loops obtained from the nanorod samples of as-grown, air-annealed and vacuum-annealed, it is found that the oxygen vacancies are the origin of the polarization reversal in ZnO nanorods. Finally, the tradeoff between the electrical and ferroelectric-like properties is also observed.

Quasars that exhibit blue-shifted, broad absorption lines (BAL QSOs) are an important probe of black hole feedback on galaxy evolution. Yet the presence of BALs is also a complication for large, spectroscopic surveys that use quasars as cosmological probes because the BAL features can affect redshift measurements and contaminate information about the matter distribution in the Lyman-α forest. We present a new BAL QSO catalog for quasars in the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). As the SDSS DR14 quasar catalog has over 500,000 quasars, we have developed an automated BAL classifier with a Convolutional Neural Network (CNN). We trained our CNN classifier on the C IV λ1549 region of a sample of quasars with reliable human classifications, and compared the results to both a dedicated test sample and visual classifications from the earlier SDSS DR12 quasar catalog. Our CNN classifier correctly classifies over 98% of the BAL quasars in the DR12 catalog, which demonstrates comparable reliability to human classification. The disagreements are generally for quasars with lower signal-to-noise ratio spectra and/or weaker BAL features. Our new catalog includes the probability that each quasar is a BAL, the strength, blueshifts and velocity widths of the troughs, and similar information for any Si IV λ1398 BAL troughs that may be present. We find significant BAL features in 16.8% of all quasars with 1.57 < z < 5.56 in the SDSS DR14 quasar catalog.

Memory disaggregation has attracted great attention recently because of its benefits in efficient memory utilization and ease of management. So far, memory disaggregation research has all taken one of two approaches: building/emulating memory nodes using regular servers or building them using raw memory devices with no processing power. The former incurs higher monetary cost and faces tail latency and scalability limitations, while the latter introduces performance, security, and management problems.Server-based memory nodes and memory nodes with no processing power are two extreme approaches. We seek a sweet spot in the middle by proposing a hardware-based memory disaggregation solution that has the right amount of processing power at memory nodes. Furthermore, we take a clean-slate approach by starting from the requirements of memory disaggregation and designing a memory-disaggregation-native system.We built Clio, a disaggregated memory system that virtualizes, protects, and manages disaggregated memory at hardware-based memory nodes. The Clio hardware includes a new virtual memory system, a customized network system, and a framework for computation offloading. In building Clio, we not only co-design OS functionalities, hardware architecture, and the network system, but also co-design compute nodes and memory nodes. Our FPGA prototype of Clio demonstrates that each memory node can achieve 100 Gbps throughput and an end-to-end latency of 2.5 𝜇𝑠 at median and 3.2 𝜇𝑠 at the 99th percentile. Clio also scales much better and has orders of magnitude lower tail latency than RDMA. It has 1.1× to 3.4× energy saving compared to CPU-based and SmartNIC-based disaggregated memory systems and is 2.7× faster than softwarebased SmartNIC solutions.

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