广义Bent函数的性质研究

本文在Zqn→Zq 上讨论了广义Bent函数的有关性质 ,给出了一类新的广义Bent函数。     

基于全固型掺镱光子带隙光纤的被动锁模全光纤环形孤子激光器

采用全固型掺镱光子带隙光纤(AS-Yb-PBGF)作增益介质并提供反常群速色散(GVD),设计了一种被动锁模全光纤环形孤子激光器。没有使用任何块状色散补偿元件。因此,该激光器腔型结构简单、紧凑、环境稳定性高,更容易实现全光纤结构。脉冲在激光腔内的传输用广义非线性薛定谔方程描述,并采用分步傅里叶方法数值模拟了该激光器的单孤子运转的动力学过程。计算时,将AS-Yb-PBGF的长度选取为0.4m,改变激光腔内单模光纤(SMF)的长度,得出了最佳运转参数:当AS-Yb-PBGF固定为0.4 m时,选择单模光纤等于0.4 m,就可以实现脉冲宽度为244 fs,脉冲能量为14 pJ和时间带宽乘积为0.32,即接近傅里叶变换极限的单孤子运转。     

Understanding the effects of various edible coatings on the storability of fresh cherry

n this work, cherries, which have a very short shelf life, were packaged after being coated with various edible coatings [whey protein isolate (WPI), chitosan and shellac]. The changes in gas composition, weight loss, Brix, pH, electrical conductivity and firmness were measured periodically up to 11 days after harvest to compare the effects of the applied coatings. Fourier transform near‐infrared (FT‐NIR) spectroscopymeasurements were also taken individually. After storage, the gas composition within trays was about 1–10% O₂ and 14–47% CO₂. The lowest weight loss (25.56%) was observed in the shellac‐coated cherries, while the highest loss (48.58%) occurred in the control group. Coated cherries exhibited a significantly lower pH and electrical conductivity than the uncoated ones. The control group presented the highest total soluble solid (TSS) values (21.29) and shellac coating had (17.25) the lowest. At the end of storage, the highest ascorbic acid (AA) content was 0.64 mg/100 ml in the shellac‐coated cherries, and the lowest AA content of 0.40 mg/100 ml was measured in the control group. Firmness was maintained by coating, especially with shellac (3.734 N), whereas the control had the lowest firmness measured (2.138 N) at the end of storage. There were differences between the absorbance spectra for the coated and control cherries at the end of storage. This research concludes that shellac coating is more effective in reducing the respiration rate and maintaining the quality parameters of cherries than chitosan and WPI coatings. Major benefits of coatings were observed in lessening the weight‐loss process and in maintaining firmness, which were also supported by the FT‐NIR measurements. Copyright © 2010 John Wiley & Sons, Ltd.     

Cerium incorporating into MCM-41 mesoporous materials for CO oxidation

Ceria doped MCM-41 materials were synthesized by surfactant-assisted hydrothermal and wet impregnation methods. All the obtained Ce-MCM-41 materials were characterized by N₂ physical adsorption, X-ray diffraction (XRD), diffuse reflectance UV–visible spectroscopy (DRUV–vis), infrared spectroscopy (IR), solid-state cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy (CP/MAS-NMR), and transmission electron microscopy (TEM). The catalytic properties were evaluated in CO oxidation under atmospheric pressure and various temperatures. The results showed that in the materials synthesized by hydrothermal method, most of Ce ions were well incorporated in the tetrahedral coordinated sites into the framework of the MCM-41 as Si/Ce molar ratio is 30 and 50. High cerium content may lead to mesostructure partial collapsing and ceria particles segregation. For CO oxidation, the catalytic activity of Ce-MCM-41 synthesized by hydrothermal method was significantly greater than that of the materials prepared by impregnation route. Over the Ce-MCM-41 materials prepared via hydrothermal technique, 100% CO conversion was achieved at 504, 514 and 528 K, respectively, as the Si/Ce molar ratio decreased from 50 to 30 and 10. For the first time, we found an interesting correlation of Q₃ species relative area in the ²⁹Si CP/MAS-NMR spectra of the Ce-MCM-41materials with the reaction rates of CO oxidation, which indicates that both surface hydroxyls and tetrahedral-coordinated Ce⁴⁺ ions in the MCM-41 take important roles in the CO oxidation.     

Description of the kinetic enzymatic browning in banana (Musa cavendish) slices using non-uniform color information from digital images

A novel methodology “fractal browning indicator” (FBI) is presented, that describes the enzymatic browning kinetic based on the use of irregular color patterns from banana slice images. It uses the fractal Fourier texture image value in a selected area, to calculate a fractal dimension (FD), which represents the complexity of color distribution. During the procedure, colors from digital images were first transformed to L^*a^*b^* space color using a transformation function (quadratic model), in order to derivate three color channels, lightness (L^*), redness (a^*), and yellowness (b^*). In the results, lightness and yellowness parameters decreased during the browning kinetic, when their respective FD values increased, indicating major color distribution complexity in a selected area analyzed during the kinetic. The redness color (a^*) did not show any statistical variation. The empirical power law model was suitable to correlate enzymatic browning kinetic data both for FBI and for the traditional method (when an L^* mean was used). However, enzymatic browning rates using the FBI method, were between 8.5 and 35 times higher than rates calculated with the traditional method.     

高紧度机织物图像倾斜的自动纠正

通过傅里叶变换方法,实现对高紧度机织物图像上位于同一直线像素点信号的周期提取。通过对不同位置直线上像素点周期的比较,发现当像素点所在直线与纱线位置平行时,得到的周期值最小。利用该结论,以图像中心为纠偏点,以0.2°为步长,遍历该点所在水平线上下20°范围的所有直线,计算对应的周期值。在这201个周期值中,最小值所对应的直线就是纱线的平行位置。将该位置旋转到水平位置,即可完成图像的纠偏。实验结果表明,该方法能够完成高紧度机织物图像倾斜的自动纠正,纠偏精度为0.2°,且对不同的织物图像具有很好的适应性。     

Rapid and non-destructive analysis of apricot fruit quality using FT-near-infrared spectroscopy

A non-destructive optical method based on near-infrared spectroscopy has been used for the evaluation of apricot fruit quality. Diffuse reflectance measurements (800–2500 nm), physical, physiological and biochemical measurements were performed individually on 877 apricot fruits from eight contrasted cultivars harvested at different ripening stages. Relationships between spectral wavelengths and quality attributes were evaluated by application of chemometric techniques based on partial least squares (PLS) on fruit set divided randomly into two groups: 598 fruits for calibration and 279 for validation. Good prediction performance was obtained for soluble solids and titratable acidity with correlation coefficients of 0.92 and 0.89 respectively and root mean square errors of prediction of 0.98% Brix and 3.62 meq 100 g⁻¹ FW respectively. For the other quality traits such as firmness, ethylene, individual sugars and organic acids, the prediction models were not satisfactorily accurate due to the high error of calibration and prediction.     

羟基酪醇酶促聚合产物的表征及其抗氧化和热稳定性

利用漆酶对羟基酪醇（hydroxytyrosol,HT）进行酶促氧化聚合,运用紫外-可见分光光度计、傅里叶红外光谱、凝胶色谱和液相色谱-质谱联用对聚合产物进行表征。结果表明,形成的聚合物呈现多分散性（D=2.1）,主要生成了三聚体、四聚体、六聚体化合物。同时,以VC和2,6-二叔丁基-4-甲基苯酚（dibutyl hydroxy toluene,BHT）为阳性对照,分别通过清除1,1-二苯基-2-三硝基苯肼自由基和热重-傅里叶变换红外光谱（thermogravimetry-Fourier transform infrared spectroscopy,TG-FTIR）联用的方法对其进行抗氧化性及热稳定性评价。结果表明,HT聚合物较HT和BHT具有更强的抗氧化性,分别约是其2.28?倍和5.7?倍,接近于VC（约是其72%）。基于热重微分曲线峰值温度（315.1?℃）和残余质量所占百分比（66.09%）结果可知,HT聚合物的热稳定性较VC（228.1?℃）、BHT（236.2?℃）和HT（314.9?℃）更强,且FTIR结果表明,HT聚合物及其他受试化合物均是以羟基断裂开始,脱氢形成醌式结构或脱水碳碳双键。这些数据可为HT的深加工利用提供理论和实践基础。