Magnetic properties and large cryogenic low-field magnetocaloric effect of HoCo<Subscript>2</Subscript> nanoparticles without core/shell structure

The HoCo₂ nanoparticles are found to be stable in air without any shell protection. The HoCo₂ nanoparticles display superparamagnetic properties between their blocking temperature of 40 K and Curie temperature of 78 K. The magnetic-entropy change increases with decreasing temperature at a certain magnetic-field change, which is ascribed to the competition between the Zeeman energy and thermal-agitation energy at low temperatures. A large magnetic-entropy change of 19.4 J kg⁻¹ K⁻¹ was found at 7.5 K in an applied-field change from 1 to 7 T, while 6.1 J kg⁻¹ K⁻¹ was achieved in a low field change of 1 T. HoCo₂ nanoparticles are useful for application of magnetic refrigeration at low temperatures.     

Double-image sharing encryption based on associated fractional Fourier transform and gyrator transform

<正>We present a novel method for realizing double-image encryption algorithm by combining the images in different transform domains.Two original images are encrypted into two interim images by fractional Fourier transform and gyrator transform,respectively.The two encrypted images can be obtained by means of the addition and subtraction of the two interim images.This is defined as a double-image sharing scheme,in which the original images are encrypted into two parts.The original images cannot be recovered only with any one of the two interim images.Numerical simulation experiments demonstrate the validity of the algorithm.     

ON J-SELFADJOINT EXTENSION OF THE PRODUCT OF TWO nTH-ORDER J-SYMMETRIC ORDINARY DIFFERENTIAL OPERATORS ON [a,b]

The problem of J-selfadjointness of the product of two nth-order J-symmetric operators on [a,b] is studied. We give a condition to ensure that the product operator is a J-selfadjoint extension.     

Arrangements on Parametric Surfaces I: General Framework and Infrastructure

We introduce a framework for the construction, maintenance, and manipulation of arrangements of curves embedded on certain two-dimensional orientable parametric surfaces in three-dimensional space. The framework applies to planes, cylinders, spheres, tori, and surfaces homeomorphic to them. We reduce the effort needed to generalize existing algorithms, such as the sweep line and zone traversal algorithms, originally designed for arrangements of bounded curves in the plane, by extensive reuse of code. We have realized our approach as the Cgal package Arrangement_on_surface_2. We define a compact and modular interface for our framework; for a given application a required small subset of the interface can be identified. Then, only this subset must be implemented. A companion paper describes concretizations for several types of surfaces and curves embedded on them, and applications. This is the first implementation of a generic algorithm that can handle arrangements on a large class of parametric surfaces.     

Titanium dioxide doped with transition metals (MxTi1?xO2, M: Ni, Co): synthesis and characterization for its potential application as photoanode

This study presents the synthesis of TiO₂ doped with different amounts of Co and Ni, starting from a simple metallic titanium powder. A successful electrophoretic deposition of these materials on ITO electrodes was achieved for its potential application as photoanodes. EDX, diffuse reflectance UV–Vis spectroscopy, and XRD measurements gave information on the chemical composition of the material and the location of the Ni or Co within the crystal structure of TiO₂. Raman spectroscopy suggests that for a higher content of doping metal above a defined percentage, the formation of metal oxide is promoted. A preliminary study of photoelectrocatalytic orange dye degradation shows higher color removal efficiency as compared to the commercial TiO₂ material.     

弹道明胶老化初级阶段的模型

用流变震荡模式研究了10 wt%浓度的弹道明胶在冷却和等温下的老化行为.对明胶从sol-gel点冷却到某个目标温度的过程,通过不同冷却速率的实验,建了一个弹性模量与温度的线性关系.不同温度下明胶的等温老化实验表明,弹性模量-时间曲线具有相似的形状.依据Normand提出的二级反应动力学模型,引入一个表征明胶老化行为的速率常数,构建了一个预测弹道明胶在老化初级阶段的弹性模量演化的模型.该模型中模量-温度关系在初始和无穷大时是直线,其他模量-温度线是近似直线,并交于sol-gel点.老化速率常数和过冷度之间符合Flory-Weaver方程.对弹性模量和老化时间进行归一化处理,可将不同温度下的老化曲线叠加成一条主曲线.     

Soft set theory based on its extension

In this paper, we point out a defect that the definitions of soft subset and soft intersection in Maji’s paper are partial definitions, and then we introduce extension of soft set to redefine and simplify operations between soft sets. At last, we obtain some algebraic properties of new soft operations.     

A “Mitsubishi emblem” tetrauclear aluminum complex containing two unsymmetric N2O2‐ligands and a symmetric NO3‐ligand as initiator for polymerization of rac‐lactide

A novel hydroxy‐, methoxy‐, and phenoxy‐bridge “Mitsubishi emblem” tetranuclear aluminum complex ( 1 ) is synthesized from an unsymmetric amine‐pyridine‐bis(phenol) N₂O₂‐ligand (H₂L¹) and a symmetric amine‐tris(phenol) NO₃‐ligand (H₂L²). Two same configuration chiral nitrogen atoms are formed in the tetranuclear Al complex upon coordination of the unsymmetric tertiary amine ligand to central Al. Complex 1 initiates controlled ring‐opening polymerization (ROP) of rac‐lactide and afford polylactide (PLA) with narrow molecular weight distributions (M_w/M_n = 1.05–1.19). The analysis of ¹H NMR spectra of the oligomer indicates that the methoxy group is the initiating group and the ring‐opening polymerization of lactide follows a coordination‐insertion mechanism. The Homonuclear decoupled ¹H NMR spectroscopy suggests the isotactic‐rich chains is preferentially formed in PLA. The study on kinetics of the ROP of lactide reveals the homopropagation rate is higher than the cross‐propagation rate, which is in agreement with the observed isotactic selectivity in the ROP of rac‐lactide. The stereochemistry of the polymerization was also supported by activation parameters. The introduction of unsymmetric ligand H₂L¹ has an effect on stereoslectivity of polymerization. This result may be of interest for the design of multinuclear metal complex catalysts containing functionalized ligands. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2084–2091