Sequential Change-point Detection for High-dimensional and non-Euclidean Data

In many modern applications, high-dimensional/non-Euclidean data sequences are collected to study complicated phenomena over time and it is of scientific importance to detect anomaly events as the data are being collected. We studied a nonparametric framework that utilizes nearest neighbor information among the observations and can be applied to such sequences. We considered new test statistics under this framework that can make more positive detections and can detect anomaly events sooner than the existing test under many common scenarios with the false discovery rate controlled at the same level. Analytic formulas for approximate the average run lengths of the new approaches are derived to make them fast applicable to large datasets

Low-Temperature Deposition of Pb(Zr,Ti)O3 Thin Films on Si Substrates Using Ba(Mg1/3Ta2/3)O3 as Buffer Layer

[[abstract]]Utilization of Ba(Mg1/3Ta2/3)O3 materials as buffer layers was found to achieve perovskite Pb(Zr,Ti)O3 (PZT) thin film growth on silicon at very low substrate temperature (∼350 °C) by in situ pulsed laser deposition (PLD). Formation of a continuous layer is of critical importance in order to use the Ba(Mg1/3Ta2/3)O3 materials as diffusion barriers for suppressing the PZT-to-Si interaction and, at the same time, as seeding layers for enhancing the crystallization kinetics of the PZT films. Perovskite and amorphous PZT thin films can be obtained by simply adjusting the ambient oxygen pressure or substrate temperature in the PLD process. The amorphous PZT films possess a markedly smaller optical refractive index than the perovskite ones (namorphous = 2.02 and nperovskite = 2.39), such that the perovskite/amorphous PZT films are a good combination for core/cladding materials for planar optical waveguides.[[fileno]]2020305010029[[department]]材料科學工程學

First-principles study, fabrication and characterization of (Zr0.25Nb0.25Ti0.25V0.25)C high-entropy ceramic

The formation possibility of a new (Zr0.25Nb0.25Ti0.25V0.25)C high-entropy ceramic (ZHC-1) was first analyzed by the first-principles calculations and thermodynamical analysis and then it was successfully fabricated by hot pressing sintering technique. The first-principles calculation results showed that the mixing enthalpy of ZHC-1 was 5.526 kJ/mol and the mixing entropy of ZHC-1 was in the range of 0.693R-1.040R. The thermodynamical analysis results showed that ZHC-1 was thermodynamically stable above 959 K owing to its negative mixing Gibbs free energy. The experimental results showed that the as-prepared ZHC-1 (95.1% relative density) possessed a single rock-salt crystal structure, some interesting nanoplate-like structures and high compositional uniformity from nanoscale to microscale. By taking advantage of these unique features, compared with the initial metal carbides (ZrC, NbC, TiC and VC), it showed a relatively low thermal conductivity of 15.3 + - 0.3 W/(m.K) at room temperature, which was due to the presence of solid solution effects, nanoplates and porosity. Meanwhile, it exhibited the relatively high nanohardness of 30.3 + - 0.7 GPa and elastic modulus of 460.4 + - 19.2 GPa and the higher fracture toughness of 4.7 + - 0.5 MPa.m1/2, which were attributed to the solid solution strengthening mechanism and nanoplate pullout and microcrack deflection toughening mechanism.Comment: 49 pages,6 figures, 4 table

Incompressible Limit of a Compressible Liquid Crystals System

This article is devoted to the study of the so-called incompressible limit for solutions of the compressible liquid crystals system. We consider the problem in the whole space $\mathbb{R}^{\mathbb{N}}$ and a bounded domain of $\mathbb{R}^{\mathbb{N}}$ with Dirichlet boundary conditions. Here the number of dimension $\mathbb{N}=2$ or 3