Effects of irradiation in combination with waxing on the essential oils in orange peel

The study evaluated the effects of waxing, irradiation dose and post‐irradiation storage time on the essential oils in orange peel. Mature oranges (Maroc late) waxed or unwaxed were treated with 1 or 2 kGy radiation and stored for 9 weeks at 20 °C and 40–50% RH. Essential oils from the peel were extracted and analysed by GC. Results showed that D ‐limonene was significantly lower in waxed oranges; levels in samples treated with 2 kGy were higher than those in non‐irradiated or treated with 1 kGy. Linalool, methyl anthranilate and 3,7‐dimethyl‐2,6‐octadienal decreased as the dose increased. Levels of linalool increased with storage time but D ‐limonene was unaffected. These results may aid in guaranteeing the quality of orange essential oils during storage time. Copyright © 2004 Society of Chemical Industry     

Fractionation and characterisation for antioxidant activity of hydrolysed whey protein

Whey protein isolate (WPI) was hydrolysed for 1 h using Alcalase, Protamex and Flavourzyme. Native WPI, hydrolysed WPI and two commercial WPI hydrolysates were subjected to fractionation by size exclusion chromatography. Antioxidant activity of WPI fractions was measured with a liposome‐oxidising system (50 µM FeCl₃/0.1 µM ascorbate, pH 7.0). Lipid oxidation was measured as thiobarbituric acid‐reactive substances (TBARS). Gel electrophoresis and amino acid analysis were run to identify the peptide composition. The influence of amino acid composition on antioxidant activity was evaluated using multivariate analysis methods (correlation analysis, principal component analysis, multiple linear regression and discriminant analysis). TBARS assays indicated the presence of antioxidant activity in all protein fractions, including non‐hydrolysed WPI. For native and hydrolysed WPI samples the first fraction (> 45 kDa) showed a higher TBARS inhibition effect (24–27%) when compared with lower‐molecular‐weight fractions and hydrolysate mixtures. In contrast, for commercial WPI hydrolysates a higher inhibitory effect was found in most of the lower‐molecular‐weight fractions (30–55%). The ability of WPI fractions to delay lipid oxidation was found to be related to the prevalence of histidine and hydrophobic amino acids. Copyright © 2004 Society of Chemical Industry     

A new methodology to appraise the physical characteristics of maize silage by image processing: effect of the ensiling process

We present a new computer vision method for measuring the physical characteristics of maize silages based on the extraction of image textural features, namely five Haralick features, the moments of order 1 and 2 on the grey levels of the image, and a fractal parameter. To show the effectiveness of these features for characterising the physical properties of the maize silage, a trial was performed on three maize cultivars (Zea mays L, a mid–early hybrid and an early hybrid) to study the effects of the ensiling process. The features could discern effects of the ensiling process on the physical properties of the maize silage. These effects were neither significant by comparing particle size distributions, nor with chemical compositions, whereas a biological response (degradation in the rumen) to the ensiling process exists. Thus image textural features seemed to give new and interesting measurements of the physical properties of the silage, explaining the biological response better than other methods. Furthermore, the ensiling effect was not the same with all the maize types and varied with the proportion of large particles in the silages. Linear relations between features before and after the ensiling process made it possible to predict a measure on a silage knowing its value on the parent forage. Copyright © 2004 Society of Chemical Industry     

三峡工程泄洪坝段表孔溢流面拉模施工技术

三峡工程泄洪坝段表孔溢流面主要采用一期预留台阶、二期拉模一次成形的方法施工,体型复杂,拉模施工难度大,施工质量要求高,在生产性试验以及对试验结果进行分析的基础上,对混凝土性能、拉模设计、施工措施等方面进行了改进,形成了一套成熟的拉模施工技术。施工结果表明,施工质量达到了设计要求。     

一种控制盐层段井眼闭合率的钻井液密度新公式

针对钻井过程中钻遇的盐层段井眼蠕变缩径问题,利用弹塑性力学理论,蠕变本构方程采用Heard蠕变方程,在平面应变和均匀地应力假设下,推导出控制井眼收缩的钻井液密度新公式,该公式与前人推导的公式不同。通过理论分析,指出产生差异的根本原因在于蠕变应力差(极坐标下表示的径向应力与切向应力之差)公式的推导上,用有限元法计算结果对理论公式进行检验,证明是可行的。对文中的力学模型采用有限元法建模、求解,利用求解结果对各应力差公式进行验证,得出:根据文中公式计算结果与有限元法计算结果完全一致,而据前人公式计算结果偏离有限元计算值较大,从而间接证明了该钻井液密度新公式的推导更严密,更准确。     

数字振荡器的实现原理与仿真编程

鉴于数字信号处理中的实时应用问题，探讨了数字滤波器的实时实现原理，包括离散时间网络结构的作用和离散时间信号处理的特点，重点介绍了实时应用中实现数字滤波器的基本思想，运用MATLAB和所导出的通用数字振荡器的系统函数对一个非正弦数字振荡器进行了仿真编程，还讨论了有关实时处理的几个重要的系统性质，表达了作者对于当前学习和应用数字信号处理方法的观点。     

Error Concealment Based on Semantic Prioritization with Hardware‐Based Face Tracking

With video compression standards such as MPEG‐4, a transmission error happens in a video‐packet basis, rather than in a macroblock basis. In this context, we propose a semantic error prioritization method that determines the size of a video packet based on the importance of its contents. A video packet length is made to be short for an important area such as a facial area in order to reduce the possibility of error accumulation. To facilitate the semantic error prioritization, an efficient hardware algorithm for face tracking is proposed. The increase of hardware complexity is minimal because a motion estimation engine is efficiently re‐used for face tracking. Experimental results demonstrate that the facial area is well protected with the proposed scheme.     

冷库多台冷风机电热融霜时间与温度双重自动控制方案

从节能和可靠运行的角度提出冷库多台冷风机电热融霜时间与温度双重自动控制方法.     

聚乙烯管材的国内外发展及应用

介绍国内外PE管材的现状和发展前景、以及管材专用料的生产、研究情况