Spectroscopic properties and thermally stable orange-red luminescence of Sm:Zr:LiNbO3 and Sm:Hf:LiNbO3 for white LED applications

LiNbO₃ crystals activated by Sm³⁺ and co-doped with Zr⁴⁺ (Sm:Zr:LN) or Hf⁴⁺ (Sm:Hf:LN) were prepared by the Czochralski method. Detailed investigation on spectroscopic properties was conducted on the frame of Judd-Ofelt (J-O) theory. The J-O intensity parameters Ω_i (i = 2, 4, 6), fluorescence branching ratios and radiative lifetime of excited level ⁴G_5/2 were determined. Furthermore, the thermal stability of the strong orange-red emissions obtained under near-UV excitation in both crystals was evaluated. As high as 100% and 97% of integrated intensities at room temperature in Sm:Zr:LN and Sm:Hf:LN respectively were retained at 423 K, demonstrating the suppressed thermal attenuation. The temperature sensing performance based on fluorescence intensity ratio strategy was degraded at higher temperatures with relatively low sensitivities, while the shift of CIE chromaticity coordinates of Sm:Zr:LN and Sm:Hf:LN in the orange-red region was insignificant, demonstrating the color constancy with increasing temperature. With the efficient and thermally stable orange-red luminescence, Sm:Zr:LN and Sm:Hf:LN could serve as promising candidate materials for near-UV excited white light-emitting diodes.     

基于超混沌双向认证的医院财务信息安全加密系统设计

由于医院财务信息中需要加密的数据较多,在信息加密过程中常出现系统稳定性差的r问题,为此将超混沌双向认证方法应用到医院财务信息安全加密系统设计中.实验证明,所设计的基于超混沌双向认证的医院财务信息安全加密系统比传统系统稳定性强.     

2种侧围加强内框总成检具结构对比分析

概述了侧围加强内框总成与周边零件的匹配关系,从检具操作的人机工程出发,描述了侧围加强内框总成检具的2种定位方式和结构设计,对比了2种定位方式对于检测结果的影响,总结了其优点和弊端,结果表明侧围加强内框总成检具采用车内方向朝下的定位方式效果更好。     

基于GA-BP的汽车风振噪声声品质预测模型

目前对于汽车风振噪声的优化研究主要以声压级（Sound pressure level，SPL）作为单一评价指标，既不能全面反映噪声的物理属性，也无法考虑人耳对噪声的主观认知过程。为准确评价风振噪声，引入声品质，运用大涡模拟（Large eddy simulation，LES）对风振噪声进行数值仿真，根据实车道路试验判断仿真的准确性；对仿真结果进行声品质客观评价与主观评价，综合声品质客观评价参数与声品质主观评价试验结果建立BP神经网络预测模型；利用遗传算法（Genetic algorithm，GA），进一步对BP神经网络的结构参数进行优化，建立GA-BP声品质预测模型。研究结果表明，GA-BP声品质预测模型在训练速度和预测精度上都优于BP神经网络预测模型。预测模型基于声品质主客观评价结果，其预测值可以代替传统的声压级评价指标，为风振噪声提供更为准确合理的评价。     

某特钢工业厂房办公楼结构设计

特钢工业厂房办公楼由2栋长90.6 m、宽34.2 m、高36.5 m的塔楼组成,两个塔楼之间2层设置钢平台,一端铰接,一端滑移.通过方案比选,两塔楼均采用钢框架(局部设支撑)结构体系,标准轴网为8.4 m×9.0m,结构布置基本对称,相邻处端部一跨存在斜柱.针对斜柱对结构的不利影响,对结构进行了 pushover分析,并采取了相应的措施;2层的钢平台跨度较大,进而做了舒适度分析,结果表明,满足规范的要求.     

Effects of rice bran fermented with Lactobacillus plantarum on palatability,volatile profiles,and antioxidant activity of brown rice noodles

Brown rice noodles (RN) are typical whole-grain products with health benefits. This study investigated the effects of rice bran fermented with Lactobacillus plantarum on palatability, volatile profiles, and antioxidant activity of brown RN. Three kinds of RN, including RN, brown RN (BRN), and bran fermented RN (BFRN), were involved in this study. The results indicated that bran fermentation reduced the cooking loss of BFRN and improved the elongation and the sensory attributes of brown RN. After fermentation, aldehydes were significantly decreased while alcohols increased, and more pleasant flavours were shown in BFRN. Fermentation increased the content of free phenolics and decreased the content of bound phenolics. Among the four major phenolics detected in this study, ferulic acid was the most abundant one in all three RN samples. The DPPH radical scavenging activity and the ferric reducing antioxidant power of free phenolics in BFRN increased significantly compared to BRN. This study proved that rice bran fermentation is an effective approach to improve palatability, enrich the flavour as well as enhance the antioxidant activity of brown RN, which may facilitate the development of processing technology for brown RN.     

Simultaneous fractionation of multiple classes of polyphenols from honeybush tea using solid-phase extraction

The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min⁻¹ of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study.     

Authenticity green coffee bean species and geographical origin using near-infrared spectroscopy combined with chemometrics

To prevent the adulteration of agricultural resources and provide a solution to enhance the green coffee bean supply chain, authentication using the near-infrared spectroscopy (NIRS) technique was investigated. Partial least square with discrimination analysis (PLS-DA) models combined with various preprocessing methods were built from NIR spectra of 153 Vietnamese green coffee samples. The model combined with the standard normal variate and the first order of derivative yielded excellent performance in predicting coffee species with the error cross-validation of 0.0261. PLS-DA model of mean centre and first-order derivative spectra also yielded good performance in verifying geographical indication of green coffee with the error of 0.0656. By contrast, the predicting abilities of post-harvest methods were poor. The overall results showed a high potential of the NIRS in online authentication practices.