成都白鹭湾生态湿地公园水生植物应用研究

在对成都白鹭湾生态湿地公园实地考察和数据分析的基础上,对其水生植物的应用现状如水生植物种类选择、配置方式、景观效果和生态功能方面进行了研究,并且结合对园区的环境空气和地表水质量的监测分析,为进一步加强白鹭湾生态湿地公园中水生植物应用及种植管理方面提出了建议,为之后的成都环城生态区建设中合理应用水生植物提供参考.     

择伐强度对杉阔混交人工林空间结构的影响

利用混交度、角尺度及以大小比数为权重的空间优势度和树种优势度4个空间结构参数,对比分析不同强度(中度34.4%、强度47.1%和极强度69.5%)择伐下杉阔混交人工林林分空间结构变化,探讨择伐强度对杉阔混交人工林空间结构的影响.结果表明:从混交程度看,择伐强度越大,越易导致林木单种聚集.与伐前相比中度择伐后林分和主要树种的平均混交度都有所增加,强度和极强度择伐后林分平均混交度明显降低,杉木平均混交度增加而木荷则显著降低;不同择伐强度在一定程度上都改善了林木的空间分布格局,中度择伐后林分的单木聚集分布改善最为明显;从空间优势看,中度或强度择伐能够维持及提高林分和主要树种空间优势度,有利于发挥林分生长潜力.综合来看,中度择伐后林分空间结构趋于合理,建议采用中度择伐作为优化杉阔混交人工林林分空间结构的有效手段.     

基于PCA和DWT的强鲁棒数字水印算法

针对传统离散小波变换(DWT)数字水印算法抗几何攻击能力较弱的问题,提出一种基于主成分分析(PCA)和DWT的新的数字水印算法。新算法对载体图像进行一级小波分解,在低频子带上用主成分分析提取出既含有高频又含有低频成分的主成分系数,将水印嵌入到提取出的主成分系数中。实验结果表明,与传统DWT水印算法相比,该算法不仅明显提高了抗剪裁、旋转等抗几何攻击能力,对加噪、图像灰度值变化等攻击也表现出了很强的鲁棒性。     

T-cell-expressed proprotein convertase furin is essential for maintenance of peripheral immune tolerance

Furin is one of seven proprotein convertase family members that promote proteolytic maturation of proproteins. It is induced in activated T cells and is reported to process a variety of substrates including the anti-inflammatory cytokine transforming growth factor (TGF)-beta1 (refs 2-4), but the non-redundant functions of furin versus other proprotein convertases in T cells are unclear. Here we show that conditional deletion of furin in T cells allowed for normal T-cell development but impaired the function of regulatory and effector T cells, which produced less TGF-beta1. Furin-deficient T regulatory (Treg) cells were less protective in a T-cell transfer colitis model and failed to induce Foxp3 in normal T cells. Additionally, furin-deficient effector cells were inherently over-active and were resistant to suppressive activity of wild-type Treg cells. Thus, our results indicate that furin is indispensable in maintaining peripheral tolerance, which is due, at least in part, to its non-redundant, essential function in regulating TGF-beta1 production. Targeting furin has emerged as a strategy in malignant and infectious disease. Our results suggest that inhibiting furin might activate immune responses, but may result in a breakdown in peripheral tolerance.     

奥氏体不锈钢小孔钻削仿真及试验研究

基于有限变形理论、虚功原理、更新的拉格朗日公式及热弹塑性本构方程,建立了金属小孔钻削加工的热力耦合有限元模型;针对难加工材料1Cr18Ni9Ti进行了小孔钻削加工过程的模拟与试验研究;对切削加工有限元模拟中的关键技术,如材料模型、工件与切屑的分离、断裂准则以及动态网格自适应技术等进行了探讨,动态模拟了麻花钻钻孔中切屑的成形过程,其中工件采用刚塑性材料模型,刀具采用考虑了温度变化的刚性材料模型.仿真结果与试验数据吻合,表明所建立的有限元模型是正确的,可用来对钻削力、扭矩及钻削温度随进给量的变化进行有效的预测.     

Effects of cavity-dispersion noncoaxiality on the generation of ultrabroadband femtosecond pulses

The effects of cavity-dispersion noncoaxiality （CDN） on the generation of ultrabroadband femtosecond pulses in KLM Ti：sapphire laser were investigated theoretically and experimentally. It was predicted that when the laser sub-cavity works near the coaxial operation point, the limitation of CDN on the bandwidth broadening is minimum, which is favorable for ultrabroadband pulse generation. On the basis of this prediction, femtosecond pulses with bandwidth of 650 to 1000 nm were directly generated from a home built KLM Ti：sapphire laser. To our knowledge, they are the broadest bandwidth pulses produced from KLM Ti：sapphire laser with similar oscillator configuration and gain crystal length of 3 mm.     

纯水相SEC法分离水溶性小金纳米簇的研究

以纯水为流动相,用PL aquagel-OH 40色谱柱与自动馏分收集器,在Agilent 1100高效液相色谱仪上,对巯基丁二酸(MSA)单层包裹的粒径约1-5 nm的水溶性小金纳米簇进行尺寸排阻色谱(SEC)分离,环境友好,操作简便,重现性好.TEM表征和粒径统计分析表明:在不同洗脱时间收集的金纳米簇馏分与相应的原始样品相比其粒径分布均得到改善,尺寸分布明显窄化.金纳米簇在所用色谱柱上的分离主要按尺寸排阻机制进行.     

近代留学生与公共文化空间的构建

近代留学生群体发展的过程,亦是公共文化空间构建的过程。具有双重文化性的近代留学生群体在国内外创建学会（社）、创办报刊,并通过它们传播文化、争论问题、互动交流、展示自我,于是公共文化空间逐渐形成。近代中国的公共文化空间与西方社会所谓的＂公共领域＂不同,前者是产生中国式＂公共领域＂的土壤,其功能的具体表现既有文学式的优雅,亦有政论式的急峻。     

青海大学人文选修课程实践教学资源开发的探索——以中文类课程为例

青海大学人文选修课在清华大学对口支援下得到长足发展.本文探索人文选修课的实践教学如何在目前青海大学的环境资源优势中展开.提出要构建学生自主学习、形式多样的实践教学体系,必然要重视开拓校内现有的环境资源优势,培养人文知识相对薄弱的学生良好的综合素质及能力.     

Higher-order duality for a class of nondifferentiable multiobjective programming problems involving generalized type I and related functions

This paper extends the class of generalized type I functions introduced by Aghezzaf and Hachimi(2000) to the context of higher-order case and formulate a number of higher-order duals to a non-differentiable multi-objective programming problem and establishes higher-order duality results under the higher-order generalized type I functions introduced in the present paper. A special case that appears repeatedly in the literature is that the support function is the square root of a positive semi-definite quadratic form. This and other special cases can be readily generated from these results.