鹅毛竹花后叶片衰老生理特性

以鹅毛竹为材料,以未开花竹为对照,分析了鹅毛竹花后叶片生理变化特性。结果表明：鹅毛竹开花后总体上叶片叶绿素、可溶性蛋白质和糖含量不断下降,并始终低于未开花竹相应指标,而可溶性糖与蛋白质含量比值、MDA含量呈不断增加趋势,并始终高于未开花竹相应指标。随着试验时间的延长,上述各指标的变幅以及与未开花竹的差距增大,表明花后叶片衰老逐渐加快。开花初期开花竹叶片SOD活性明显高于未开花竹,而POD、CAT活性明显低于未开花竹,后期开花竹各保护酶活性的变幅明显大于未开花竹,表明鹅毛竹开花后保护酶系统间的平衡失调。推测活性氧的大量产生以及保护酶系统间平衡失调导致的膜脂过氧化程度增加,膜以及蛋白质等生物大分子结构与功能的破坏及其降解等可能是开花竹花后叶片衰老加快的主要原因之一。     

Stable initialization scheme for K -means clustering

Though K-means is very popular for general clustering, its performance which generally converges to numerous local minima depends highly on initial cluster centers. In this paper a novel initialization scheme to select initial cluster centers for K-means clustering is proposed. This algorithm is based on reverse nearest neighbor (RNN) search which retrieves all points in a given data set whose nearest neighbor is a given query point. The initial cluster centers computed using this methodology are found to be very close to the desired cluster centers for iterative clustering algorithms. This procedure is applicable to clustering algorithms for continuous data. The application of proposed algorithm to K-means clustering algorithm is demonstrated. Experiment is carried out on several popular datasets and the results show the advantages of the proposed method. Foundation item: Supported by the National Natural Science Foundation of China (60503020, 60503033, 60703086), the Natural Science Foundation of Jiangsu Province (BK2006094), the Opening Foundation of Jiangsu Key Laboratory of Computer Information Processing Technology in Soochow University (KJS0714) and the Research Foundation of Nanjing University of Posts and Telecommunications (NY207052, NY207082)     

FDTD计算共面波导馈电双频天线

基于共面波导传输结构的诸多优越特性,如低剖面、重量轻和低成本等,共面波导结构成为一个研究的重点.首先,给出一个共面波导馈电的双频天线结构,并分析了其工作原理,得出了工作频率与几何尺寸的定性关系;接着,介绍了时域有限差分法对共面波导馈电双频天线进行仿真计算时的一些关键技术,如激励源的设置,完全匹配层的设置和近远场外推技术,特别是激励源的设置,引入了模式匹配的激励设置方法,与传统激励源的设置相比,减少了计算时间与内存的需要;最后,给出了天线特性的计算结果与实测结果,具有较好的一致性,满足了双频天线工作的基本要求;同时,电场分布证明了双频工作的机理,对此种天线设计参数选取有一定指导意义.     

Al2O3-SiC-C浇注料的应力-应变行为

为了解 Al2O3-SiC浇注料力学性能及其从发生形变至断裂前的行为特征,采用对试样循环加载、卸载和变温的方式,对材料的弹性形变、塑性形变和黏滞形变进行了研究,并测量了Al2O3-SiC浇注料在不同温度下的弹性模量.结果表明,载荷影响着材料塑性形变开始温度,载荷越大,塑性变形开始温度越低;黏滞形变与载荷无关,仅取决于试验温度;结合剂种类和SiC含量对浇注料的力学性能产生明显的影响.     

n-Pentylamine-intercalated layered perovskite-type oxide

A novel n-pentylamine-intercalated layered perovskite-type oxide, C5H11NH3-Sr2Nb3O10, was prepared and characterized by using XRD, FT-IR, Raman spec-trascopy, and elemental analysis. It was shown that the intercalated n-pentylamine adopted a bilayer formation with some overlap and tilt, and the lattice of the perovskite layer was distorted due to the intercalation of n-pentylamine. The as-prepared sample gave clear electric hysteresis loop and did not show fatigue after 1011 switching circles, and therefore, could be considered as a new kind of fatigue-free ferroelectric materials.     

Early diversification of birds: Evidence from a new opposite bird

A new enantiornithine bird Longipteryx chaoyangensis gen. et sp. nov. is described from the Early Cretaceous Jiufotang Formation in Chaoyang, western Liaoning Province. This new bird is distinguishable from other known enantiornithines in having uncinate processes in ribs, elongate jaws, relatively long wings and short hindlimbs, and metatarsal Ⅳ longer than metatarsals Ⅱ and Ⅲ. This new bird had probably possessed (ⅰ) modern bird-like thorax which provides firm attachment for muscles and indicates powerful and active respiratory ability; (ⅱ) powerful flying ability; (ⅲ) special adaptation for feeding on aquatic preys; and (ⅳ) trochleae of metatarsals Ⅰ——IV almost on the same level, an adaptation for perching. The new bird represents a new ecological type different from all known members of Enantiornithes. It shows that enantiornithines had probably originated earlier than the Early Cretaceous, or this group had experienced a rapid radiation right after it first occurred in the early Early Cretaceous.     

动态生成程序映象的新方法

介绍了1种新的代码优化的新方法－Just in Time Code Layout,它不同于传统的静态链接生成可执行程序映象文件的方法,而是在运行时通过动态链接生成招待程序的映象。对此研究了此方法对程度映象和传统方法生成的程序映象及用Pettis方法优化生成程序映象3者之间在运行时Cache性能的差异,证明了这种方法对程序运行的明显效果。     

利用自动频率分配算法规划GSM网络

借助科学的规划软件,通过自动频率复用分配算法,进行网络的预测和设计,使网络频率资源获得最佳的利用率,有效减少小区干扰。     

关于M^x／Gn／1排队系统的分析

利用嵌入马尔可夫链法研究M^x/Gn/1排队系统,求得了M^x/Gn/1系统的稳态队长的母函数,并验证了该结果的正确性。     

褐煤提质废水污染特征分析

由于褐煤矿质组成的特点和提质工艺的复杂性,决定了褐煤提质废水在水质组成及含量上具有自身独特的环境学特征。为了建立高效、稳定以及出水水质安全的褐煤提质废水处理技术体系,采用常规分析、色谱、质谱等技术,分析研究了洗选蒸脱法褐煤提质工艺废水的污染特性和特征污染物。研究结果表明,褐煤提质加工的废水的CODCr、BOD5、NH4+-N、挥发酚、氰化物等常规污染指标较高,可生化性差,有机污染组分复杂且不同组分含量差异较大,需经过严格的水处理工艺才能满足污水排放标准的要求。研究为褐煤提质废水处理技术的开发提供了科学依据。