离子色谱-紫外检测器测定食品中亚硝酸盐和硝酸盐

建立了离子色谱-紫外检测器测定食品中亚硝酸盐和硝酸盐的分析方法。样品经超声提取后,以3.6 mmol/L Na_2CO_3溶液为流动相,经Metrosep A supp7-250阴离子交换分析柱,于210 nm处进行紫外检测。结果表明该方法在0.025～0.20 mg/L(亚硝酸盐)、0.10～2.0 mg/L(硝酸盐)范围内具有良好的线性关系,相关系数r均在0.999以上。亚硝酸盐和硝酸盐的检出限分别为0.004 5 mg/L和0.017 2 mg/L,检测下限分别为0.018 mg/L和0.068 mg/L,实际样品加标回收率分别为81.3%～87.3%和98.3%～103.1%,相对标准偏差小于5%。实验表明,该方法简便、灵敏,可用于测定食品中的亚硝酸盐和硝酸盐。     

基于可靠度理论对滑移式落石的稳定性及敏感性分析

汶川地震引发了大量的地质灾害,其中坡表停留孤石的判定及治理成为了灾害重建的难题。针对偏心滑落式孤石的稳定性极限特征,用可靠度理论,建立其可靠度判定极限状态方程;并根据现场量测及概率统计方法,对函数中孤石处的坡脚α、孤石的内摩擦角φ、单位长度危岩体重力G、孤石黏聚力c、孤石高度h等基本变量的均值、变异性系数及分布特征进行确定。基于以上研究成果,建立了偏心滑移式孤石稳定性可靠度指标计算方法;同时对各基本变量的可靠度敏感性进行研究。研究结果表明:孤石的倾角的可靠度敏感性最高,其次是孤石的单位长度重量、内摩擦角和黏聚力指标;而孤石的高度对其没有影响。     

Fast Fractal Image Encoding Based on Special Image Features

The fractal image encoding method has received much attention for its many advantages over other methods, such as high decoding quality at high compression ratios. However, because every range block must be compared to all domain blocks in the codebook to find the best-matched one during the coding procedure, baseline fractal coding (BFC) is quite time consuming. To speed up fractal coding, a new fast fractal encoding algorithm is proposed. This algorithm aims at reducing the size of the search window during the domain-range matching process to minimize the computational cost. A new theorem presented in this paper shows that a special feature of the image can be used to do this work. Based on this theorem, the most inappropriate domain blocks, whose features are not similar to that of the given range block, are excluded before matching. Thus, the best-matched block can be captured much more quickly than in the BFC approach. The experimental results show that the runtime of the proposed method is reduced greatly compared to the BFC method. At the same time, the new algorithm also achieves high reconstructed image quality. In addition, the method can be incorporated with other fast algorithms to achieve better performance. Therefore, the proposed algorithm has a much better application potential than BFC.     

一类亚循环群的Coleman外自同构群

利用群的射影极限性质,给出了一类亚循环群的Coleman外自同构群或者是1或者是一个初等阿贝尔2-群。