Multi-performance characterization analysis of diameter and taper angle on alumina ceramic via using pulsed ultraviolet laser percussion drilling method

This paper presents the optimal conditions for the ultraviolet laser percussion drilling of alumina materials intended for use in heat sinks. The Taguchi method and grey relational analysis, along with the consideration of multiple quality characteristics, were applied for determining the optimal parameters. The entrance diameter and taper angle of the drilled hole were affected by the material processing parameters, including laser power, pulse duration, focal plane position, and number of pulses. The Taguchi method and grey relational analysis were used for assessing the effects of the operational parameters on multiple performance characteristics. Nine experiments based on an orthogonal array were performed. According to the results, the optimal process parameters were as follows: laser energy density, 3.82 J/cm²; focal plane position, 0.1 mm; number of pulses, 20 shots; and single pulse duration, 3 ms. Analysis of the grey relational grade revealed that the focal plane position was the most dominant parameter.     

Study on a new green phosphor Ca12Al14O32Cl2: Tb3+ derived from Tb-doped Ca-Al layered double hydroxide

A new green phosphor Ca₁₂Al₁₄O₃₂Cl₂: Tb³⁺ derived from Tb-doped Ca-Al layered double hydroxide (Tb-doped CaAl-LDH) was prepared through phase transition route. The X-ray diffraction measurement results revealed that the Tb-doped CaAl-LDH transformed into Ca₁₂Al₁₄O₃₂Cl₂:Tb³⁺ phase at 600 °C. With temperature varying from 600, 800–1000 °C, the crystallinity of the Ca₁₂Al₁₄O₃₂Cl₂:Tb³⁺ phase gradually improved. Compositional analyses suggested the chemical formula of the Ca₁₂Al₁₄O₃₂Cl₂:Tb³⁺ phase estimated to be Ca₁₂Al_13.52Tb_0.48O₃₂Cl₂. The Ca₁₂Al_13.52Tb_0.48O₃₂Cl₂ phase can be efficiently excited by near ultraviolet light and show strong green emissions attributed to ⁵D₄→⁷F_J (J = 5, 6) transition of Tb³⁺. The present Ca₁₂Al_13.52Tb_0.48O₃₂Cl₂ may be a promising candidate for green phosphor applied in LED.     

Möbius transformation and a version of Schwarz lemma in octonionic analysis

The octonion is a generalization of complex to noncommutative and nonassociative space which has closed relation with exception geometries, wave equation, Yang‐Mills equations, black hole, string theory, and special relativity. In this paper, the Möbius transformation in this manner is first introduced, and some properties are discussed about the transformation in octonionic analysis. Some technique lemmas will be given to solve the problems caused by the weak form of associativity. These versions of Schwarz lemma and Schwarz‐Pick lemma are first studied in octonionic setting which will invoke integral representation formula for harmonic function and Möbius transformations. This will generalize the corresponding results which appear in the classical function theory to nonassociative space and may give new energy for the development of physics.     

Steady vortex patches near a nontrivial irrotational flow

In this paper, we study the vortex patch problem in an ideal fluid in a planar bounded domain. By solving a certain minimization problem and studying the limiting behavior of the minimizer, we prove that for any harmonic function q corresponding to a nontrivial irrotational flow, there exists a family of steady vortex patches approaching the set of extreme points of q on the boundary of the domain. Furthermore, we show that each finite collection of strict extreme points of q corresponds to a family of steady multiple vortex patches approaching it.     

Probing Ag nanoparticle surface oxidation in contact with (in)organics: an X‐ray scattering and fluorescence yield approach

Characterizing interfacial reactions is a crucial part of understanding the behavior of nanoparticles in nature and for unlocking their functional potential. Here, an advanced nanostructure characterization approach to study the corrosion processes of silver nanoparticles (Ag‐Nps), currently the most highly produced nanoparticle for nanotechnology, is presented. Corrosion of Ag‐Nps under aqueous conditions, in particular in the presence of organic matter and halide species common to many natural environments, is of particular importance because the release of toxic Ag⁺ from oxidation/dissolution of Ag‐Nps may strongly impact ecosystems. In this context, Ag‐Nps capped with polyvinolpyrrolidone (PVP) in contact with a simple proxy of organic matter in natural waters [polyacrylic acid (PAA) and Cl^? in solution] has been investigated. A combination of synchrotron‐based X‐ray standing‐wave fluorescence yield‐ and X‐ray diffraction‐based experiments on a sample consisting of an approximately single‐particle layer of Ag‐Nps deposited on a silicon substrate and coated by a thin film of PAA containing Cl revealed the formation of a stable AgCl corrosion product despite the presence of potential surface stabilizers (PVP and PAA). Diffusion and precipitation processes at the Ag‐Nps–PAA interface were characterized with a high spatial resolution using this new approach.     

Analysis on dependence of phase matching angle on temperature in KDP crystal

The dependence of the phase matching (PM) angle on temperature in type-I second harmonic generation (SHG) and type-II third harmonic generation (THG) of KDP is experimentally investigated. The experimental results show that as the crystal temperatures vary by 1 °C, the external PM angles of the KDP doubler and tripler change 100 μrad and 220 μrad, respectively. The PM angle of KDP tripler is more sensitive to temperature variation than is that of the KDP doubler. Comparing the numerical calculations and the previous reports, a discrepancy has been found among the different reported results. Based on the analytical solution of the temperature dependence of the SHG process it is shown that a small error in the thermo-optic coefficients of the crystal is the main factor source of the discrepancy.     

Theory of modified thermally stimulated current and direct determination of trap level distribution

In order to investigate the trap level distribution in polymer films, a new method is proposed based on modified thermally stimulated current (TSC) theory and numerical calculation of the TSC measurement. In this method, a new function is defined to weight the contribution of every trap level to the external current. The demarcation energy is used to study the trap emptying process. The modified TSC theory shows that only the electrons with trap levels very close to the demarcation energy can significantly contribute to the external circuit at any instant temperature. Based on this method, the trap level distribution of the DuPont original polyimide film 100HN and nanocomposite polyimide film 100CR are investigated as an application example. The effectiveness of the method is confirmed by the experiments. The experimental results show that the trap level density in the 100CR PI films is about six times larger than that in the 100HN PI films through the investigated trap level ranges 06–1.3 eV. The increased traps in 100CR should be introduced by nanofillers, probably come from the interfaces formed between nanofillers and the polymer matrix.     

Levitation performance of the magnetized bulk high-Tc superconducting magnet with different trapped fields

To a high-T_c superconducting (HTS) maglev system which needs large levitation force density, the magnetized bulk high-T_c superconductor (HTSC) magnet is a good candidate because it can supply additional repulsive or attractive force above a permanent magnet guideway (PMG). Because the induced supercurrent within a magnetized bulk HTSC is the key parameter for the levitation performance, and it is sensitive to the magnetizing process and field, so the magnetized bulk HTSC magnets with different magnetizing processes had various levitation performances, not only the force magnitude, but also its force relaxation characteristics. Furthermore, the distribution and configuration of the induced supercurrent are also important factor to decide the levitation performance, especially the force relaxation characteristics. This article experimentally investigates the influences of different magnetizing processes and trapped fields on the levitation performance of a magnetized bulk HTSC magnet with smaller size than the magnetic inter-pole distance of PMG, and the obtained results are qualitatively analyzed by the Critical State Model. The test results and analyses of this article are useful for the suitable choice and optimal design of magnetized bulk HTSC magnets.     

"量身定做"单光子波包:在量子网络中控制光子/自旋量子界面

文章简要地介绍了如何在量子网络中控制量子界面动力学以实现静态量子比特和动态量子比特的相互转换．具体言之，该界面由半导体量子点、固体光学微腔以及光学波导管构成，静态及动态比特分别为量子点中的电子自旋和波导管中的单光子波包所携带．界面动力学的控制则是基于对量子点、微腔和波导管耦合系统的量子电动力学的严格求解．据此可实现网络中两个远距离节点间的量子态传输、交换以及确定性的建立量子纠缠等量子操作．上述量子界面亦可用于任意指定波形的单光子源或者单光子探测装置。