Constructing novel red-emitting Ba2Y0.8Eu0.2NbO6:Mn4+ phosphors for multi-type luminescent thermometers and high-security anti-counterfeiting films

To date, luminescent materials have been preferably used for non-contact optical thermometers. In this manner, novel red-emitting Ba₂Y_0.8Eu_0.2NbO₆:Mn⁴⁺ (BYEN:Mn⁴⁺) phosphors were designed for multi-type non-contact luminescent thermometers based on the dual-emission states and temperature-dependent lifetime (TDL) models. In the temperature range of 303–483 K, the sensing sensitivities based on the dual-emission states of (⁵D₀→⁷F₂, ²E_g→⁴A_2g) and (⁵D₀→⁷F₁, ²E_g→⁴A_2g) were estimated. Especially, the maximum absolute sensing sensitivity (S_a) was found to be about 0.1558 K^-1 for the BYEN:0.007Mn⁴⁺ phosphor based on the ⁵D₀→⁷F₁ and ²E_g→⁴A_2g positions. This phosphor also exhibited good relative sensing sensitivity (S_r) (0.0186 K^-1) based on the ⁵D₀→⁷F₂ and ²E_g→⁴A_2g states. Besides, the relative sensing sensitivities (S_R) at ⁵D₀→⁷F₁ and ²E_g→⁴A_2g transitions were estimated to be 0.0034 and 0.0194 K^-1, respectively with the help of the TDL technique. In the light of these results, novel red-emitting Ba₂Y_0.8Eu_0.2NbO₆:Mn⁴⁺ phosphors are expected to be a potentially attractive candidate for applications in multi-type luminescent thermometers. Finally, a novel unique polydimethylsiloxane film exhibiting tricolor-luminescent emissions was introduced and further suggested for high-security anti-counterfeiting.     

Solid‐Phase Synthesis of a Seventh‐Generation Inverse Poly(amidoamine) Dendrimer: Importance of the Loading Ratio on the Resin

Here, this study overcomes the current barriers to efficient solid‐phase synthesis of high‐generation dendrimers by decreasing the loading ratio on the resin. G7 inverse poly(amidoamine) dendrimer is now prepared, for the first time, through a solid‐phase synthesis using only 50% of the available reactive sites and by choosing a large resin. This preparation takes only 15 d to afford highly pure product in 80% yield with precipitation being the only purification procedure used. The results clearly show the amount of the initial monomer loaded on the resin to be a vital factor for the ability to use solid‐phase synthesis to produce large dendrimers. This finding also sets stage for the applications of solid‐phase synthesis for the preparation of other macromolecules.

     

Optimisation of alignment materials for minimising residual retardation in in-plane switching liquid crystal display

The light leakage in a black state of in-plane switching (IPS) liquid crystal display (LCD) associated with rubbing process has been investigated. The mechanical rubbing process with a cloth caused orientation disorders in the liquid crystal directors and these partial orientation disorders result in residual retardations of the IPS LCD, causing the light leakages at the black state. In this study, we theoretically estimated how the light leakage is associated with the rubbing uniformity using 2 × 2 Jones matrix equation and also experimentally confirmed how it is associated with structural properties of the alignment layer. The light leakage was clearly reduced in the alignment layer with reduced crystallinity and flexibility.     

异相成核和拉伸诱导对生物基PHBV复合纤维结晶结构与力学性能的影响

采用熔融纺丝法制备了聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)/二硫化钨(WS_2)复合纤维.利用示差扫描量热仪(DSC)、热台偏光显微镜、二维广角射线衍射仪(2D-WXRD)、纤维强力仪研究了WS_2异相成核作用和牵伸诱导作用对纤维的结晶结构和力学性能的影响.研究表明,WS_2显著提高了PHBV的结晶温度,当使用2 wt%WS_2时,复合材料的结晶温度提高到115~130oC,比纯PHBV(99~105oC)提高了约25oC.WS_2不仅没有影响PHBV球晶的径向生长速率,且明显提高了PHBV/WS_2复合材料的晶核密度,熔体成核活性Φ由1.0降低为0.49.随着牵伸倍率和WS_2用量的增加,纤维的拉伸强度呈现出先增加后减小的趋势.当添加1 wt%WS_2并采用单向牵伸3.8倍时,纤维中的晶体取向产生了β晶结构,使复合纤维的拉伸强度由纯PHBV的37 MPa提高至155 MPa,断裂伸长率由2.4%增加至45%.     

Ni掺杂对Ni/MgO体系中电荷分配影响

采用密度泛函理论(DFT)计算方法,研究了载体Ni掺杂对Ni/MgO催化剂的电子结构及其对CH_4/CO_2重整反应的影响。结果显示,随着载体Ni:Mg比的增加,CH_4解离吸附和CH_x氧化过程的反应能垒均会随之升高,CH也更容易产生热解C,从而导致催化剂的活性和稳定性的下降。通过分析重整过程的Hirshfeld电荷分配,发现金属载体之间电子转移的方向会随着载体中Ni含量的上升由载体向Ni金属转移变为由Ni金属向载体转移。当Ni金属富电子时,反应物活化时电子的转移主要发生在表层Ni原子与吸附物种之间,参与氧化的CH_x物种为CH_2;当Ni金属缺电子时,反应物活化时Ni簇的电子结构基本保持稳定,电子主要在载体表层的Ni原子与反应物之间转移,CH是主要参与氧化的CH_x物种。     

Limit theorems for random walks

We consider a random walk $S_{\tau }$ which is obtained from the simple random walk $S$ by a discrete time version of Bochner’s subordination. We prove that under certain conditions on the subordinator $\tau$ appropriately scaled random walk $S_{\tau }$ converges in the Skorohod space to the symmetric $\alpha$-stable process $B^{\alpha }$. We also prove asymptotic formula for the transition function of $S_{\tau }$ similar to the Pólya’s asymptotic formula for $B^{\alpha }$.     

具有缺失数据的Eichhorn模型

为了解决在Eichhorn乘法扰动模型中存在的项目无回答问题,对敏感变量总体均值在辅助变量总体均值已知与未知条件下提出了比率插补方法.理论比较和数值模拟得出的结果表明提出的插补方法比传统的方法效率更高.     

基于在线HHT和SVM的汽油机轻微漏气故障识别方法

针对汽油机轻微漏气故障会被闭环反馈控制所掩盖,提出了一种基于在线希尔伯特变换(Hilbert-Huang Transform,HHT)和支持向量机(Support vector machine,SVM)的两阶段微小故障识别方法(Online HHT-SVM,OHS).第一阶段在嵌入式两滑动时间窗内通过HHT对发动机空燃比数据流进行在线时频分析,以实时获取空燃比发生异常的时刻;第二阶段通过SVM对异常时刻的数据流故障模式进行离线识别.根据氧传感器信号特征,对经验模态分解(Empirical mode decomposition,EMD)算法进行了改进,并从理论上进行了证明.基于两款发动机的实际运行数据验证了该方法的有效性.     

三维空间中带非线性阻尼项的等熵欧拉方程组轴对称解的爆破

研究了三维空间中带非线性阻尼项的可压缩等熵欧拉方程组Dirichlet初边值问题.采用泛函方法,定义几种不同的泛函,当初始速度足够大时分别得到了经典解在某一时间内必定爆破的结论.由于出现了非线性阻尼项,较之线性阻尼的情形,经典解爆破的难度随之增加.     

Characterization of high‐aspect‐ratio periodic structures by X‐ray photoelectron spectroscopy

X‐ray photoelectron spectroscopy (XPS) is a powerful surface characterization technique often relied on for quantification of surface species and coverages. Investigation of silicon microrods, considered a model for high‐aspect‐ratio structures, at different angles with respect to substrate normal was determined to have a significant impact on the relative sensitivity of surface‐bound species on rods relative to the base substrate. Comparison between planar silicon and microrod arrays demonstrates that the angular dependence is complicated and that careful studies must optimize conditions to differentiate between surfaces. In addition, the use of reverse angle resolved XPS, where the substrate is turned away from the X‐ray source, is shown to assist in simplifying the spectrum by removing underlying signal from the substrate near the base. Copyright © 2016 John Wiley & Sons, Ltd.