417 resultados para 3651-1252


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有毒有机污染物(TOP)在土壤-植物系统暴露动态模型是TOP生态风险评价和管理的必要手段,是目前TOP环境科学研究的活跃领域。以往主要以经典的对流-扩散方程(CDE)为基础的建模途径存在诸多局限:i.基本过程机制和理论研究尚不完善,制约着系统模型的研究水平;ii.模型过于复杂,在应用上存在很大困难,;iii.普遍缺乏野外实际观测结果的检验。需要开辟和发展新的TOP在土壤-植物系统暴露动态模型正是在此方面的突破。EDMOCSS很大程度上克服了经典建模途径的局限,既包括几乎所有基本过程及其目前普遍接受和应用的理论,模型的结构又不很复杂,具有良好行为特征,应用上较方便。以优先有机污染物-菲(phenanthrene)为供试化学品的野外慢速土地处理系统(SR-LTS)小区动态观察结果,很好地验证了EDMOCSS核心模型-耕作层土壤分室模型的结果,表明了EDMOCSS有较好模拟预测能力,为EDMOCSS的深入研究和应用奠定了基础。

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<正>加卸载响应比(Yin et al.,2000)是一种中短期地震预测方法,该方法依据潮汐力在地震破裂面上引起的库仑破坏应力变化计算加卸载响应比,并根据其时间序列的演化预测未来地震。我们研究了长期构造加载在地震断层面上引起的应力场变化对加卸载响应比演化的调制作用,发展了一种使用震前应力积累区域取

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分析了对岩体中爆炸能量分布和爆腔内压力研究的现状, 为进行这方面的研究, 在块体离散元基础上独立开发了可变形多尺度计算模型和爆源模型, 改进后的数值模型适合研究爆源近区的爆炸效应. 通过该模型对岩体中爆腔内压力和爆炸能量分布进行了数值模拟, 分析了爆腔内压力脉动特征, 指出爆源近区岩体结构性质对爆腔内压力脉动规律影响不大, 爆腔内压力峰值与炸药量无关; 结合热力学和弹性力学知识分析了不同条件下爆炸能量分布规律, 研究了岩体破坏对爆炸能量分布的影响, 给出了岩石断裂破坏消耗能量、变形能、用于抛掷的能量的比例

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在加速器上利用束箔光谱方法 ,测量了Ti离子的高电离态光谱

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黄土高原地区的水土流失和荒漠化,不仅危害当地人民的生产和生活,而且危及黄河下游的安澜,致使黄土高原水土流失问题一直是中华民族的心腹之患。为此,江泽民总书记在1997年曾批示,要“再造一个山川秀美的西北地区”。1999年朱镕基总理在陕北延安和水土保持研究所考察时讲到“黄河中上游各省区要解放思想,采取退田还林(草)、封山绿化、个体承包、以粮代赈的措施,大搞植树种草,改善生态环境,为根治黄河奠基,为子孙后代造福”。为了改善黄土高原的生态环境,我们在大量调研基础上,就黄土高原生态环境建设、植被恢复和水土保持等问题提出一些初步意见。 一、生态环境建设中存在的主要问题 1.粮食生产能力低,基本口粮难以自给 黄土高原现有耕地512万公顷,粮食生产能力为90亿公斤,人口 3000多万,每年粮食短缺达20多亿公斤。随着山川秀美工程的实施、生态环境的改善与人民生活的提高,未来黄土高原粮食短缺将日益增加。据我们分析,假设黄土高原人口增长率为零、13%。(目前自然增长率)和15%。(机械增长率),2010年黄土高原粮食需求量分别为155亿公斤、175亿公斤和 180亿公斤。由于退耕还林还草,粮食生产能力损失15亿公斤,届时黄土高原粮...

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Electrostatic assembly of one species can be realized using gelatin as a polyampholyte. Under suitable conditions where the electrostatic attraction and repulsion were both significant and in balance, linear growth of multilayers driven by electrostatic interactions was sustained over many successive assembly steps, and the maximum amount of adsorption of each layer was reached when the solution pH was around the isoelectric point. The rearrangement of the adsorbed chains after drying was confirmed by contact angle analysis. In addition with only one species involved, the assembled thin films should be chemically uniform rather than layered.

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A simple, large scale, and one-step process for the preparation of tris(2,2'-bipyridyl)ruthenium(I) (Ru(bpy)(3)(2+)) doped SiO2@carbon nanotubes (MVNTs) coaxial nanocable used for an ultrasensitive electrochemiluminescence (ECL) is presented for the first time. More importantly, a directly coated as-formed functional material on ITO electrode surface exhibits excellent ECL behavior, good stability, and high sensitivity in the presence of tripropylamine (TPA). This novel functional material will find potential applications in biosensor, electrophoresis and electroanalysis.

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A thin film electroluminescence cell with the structure of ITO/PPV/PVK:Eu(TTA)(4)C5H5NC16H33:PBD/Alq(3)/Al has been fabricated. Red emission with a very sharp spectral band at 614nm was observed and a maximum luminance of 20cd . m(-2) at 36V was obtained from the spin-coated device. The full width at half maximum of luminescent spectrum is less than 10nm.