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101.
Persistent organic pollutants (POPs) are major environmental concern due to their persistence, long-range transportability, bio-accumulation and potentially adverse effects on living organisms. Analytical chemistry plays an essential role in the measurement of POPs and provides important information on their distribution and environmental transformations. Much effort has been devoted during the last two decades to the development of faster, safer, more reliable and more sensitive analytical techniques for these pollutants. Since the Stockholm Convention (SC) on POPs was adopted 12 years ago, analytical methods have been extensively developed. This review article introduces recent analytical techniques and applications for the determination of POPs in environmental and biota samples, and summarizes the extraction, separation and instrumental analyses of the halogenated POPs. Also, this review covers important aspects for the analyses of SC POPs (e.g. lipid determination and quality assurance/quality control (QA/QC)), and finally discusses future trends for improving the POPs analyses and for potential new POPs. 相似文献
102.
作为生物柴油原料的麻疯树在我国已呈现快速发展态势,但对其未来发展潜力尚缺乏实证研究.目的是通过构建麻疯树生产决策模型,模拟分析不同情景下我国西南地区麻疯树发展潜力.研究结果表明:1)在基准方案下,麻疯树种籽产量与生物柴油产量可以达到320万吨和93万吨,但难以达到预期发展目标.2)影响麻疯树发展潜力的最重要因素是技术进步、产出品(麻疯树种籽)与主要投入品(劳动与肥料)价格,其中技术进步是提升未来麻疯树发展潜力的关键,而麻疯树种籽与肥料等价格取决于能源价格.在发展以麻疯树为原料的生物柴油产业发展战略上,近期国家应把加强优良品种的选育与丰产栽培技术作为重点,未来发展需密切关注能源市场的变化. 相似文献
103.
Zhao Yanting Ma Weiguang Xiao Liantuan Li Changyong Zhang Linjie Jia Suotang 《中国光学快报(英文版)》2002,11(2)
In this paper, by numerical analysis the relationship of the modulation broaden index with modulation index using high-order-harmonic detection is investigated. Using the voltage modulation the 2f,4f and 6f harmonic signals about the reflection spectroscopy of 6S1/2(F=4)→6P3/2 transition of the cesium D2 line are also be measured. The experimental results are in good agreement with the theoretical predictions. It is found that narrower line-width can be achieved by higher-harmonic detection than the line-width detected by direct absorption when the modulation index is smaller than 1.81, 2.98 and 4.14 for 2f, 4f, and 6f signals, respectively. 相似文献
104.
Xia Yin Weiguang Zhang Jun Fan Feng Xian Wei Chian Sing Lai Edward R. T. Tiekink 《应用有机金属化学》2003,17(11):889-890
The centrosymmetric structure of {Zn[S2CN(CH2Ph)2]2}2(4,4′‐bipy) features chelating dithiocarbamate ligands so that a trigonal bipyramidal NS4 coordination geometry for zinc results. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
105.
自适应免疫遗传算法 总被引:8,自引:0,他引:8
遗传算法(GA)是基于自然遗传规则随机搜索技术的一种进化算法,但是随着实际结构的大型化和复杂化,它往往出现过早收敛的现象。在研究了算法的编码方式、控制参数和算子操作之后,就其全局收敛性的不足,提出动态自适应策略以改进其性能,在基本遗传算子的基础上,采用了免疫遗传算子和保优策略。其中免疫算子可以防止交叉变异中的个体退化,自适应策略则保持了种群的多样性,以此保证遗传算法尽快收敛到全局最优解,称之为自适应免疫遗传算法(AIGA)。随后以经典的十杆桁架结构优化问题作为例子说明算法的优越性,结果表明AIGA在随机结构优化中计算有效、结果可靠。 相似文献
106.
在分析顺层边坡受力状况的基础上,当边坡的坡脚未被破坏时,将顺层边坡视为弹性地基上的悬臂梁,由此提出其失稳破坏的力学模型。应用弹性理论求出在力作用下悬臂梁的应力状态,并根据摩尔-库伦准则,导出可判定其稳定性的安全系数计算公式,得出了顺层边坡处于极限平衡状态极限长度。同时通过实例计算,将文中方法与应用突变理论所得结果对比,验证了本文方法的可行性。 相似文献
107.
108.
LiLi Zhang Weiguang Zhang Junwu Zhu Xujie Yang 《Journal of solid state chemistry》2005,178(3):761-768
Ultrafine-layered lanthanon titanates K2Ln2Ti3O10 (Ln=La, Nd, Sm, Gd, Dy) were fabricated at relatively low temperature by a stearic acid method (SAM). The obtained products were characterized by FT-IR, X-ray diffractometer, DTA-TG, scanning electron microscopy, transmission electron microscopy and BET experiments. The photocatalytic activity of the obtained products was studied and was compared with that of solid-state reaction (SSR) using photodecomposition of methyl orange as the model system. Results showed that by using SAM, the fabricating temperature was lowered (from 1100 to 800 °C) and the reacting time was shortened (from at least 11-2 h). Comparing with the product of traditional SSR, the particle size of K2Ln2Ti3O10 synthesized by SAM is smaller, BET surface area is higher (more than 16.97 m2/g), and photoreactivity is better. It was very interesting to find the difference in d(002) of obtained K2Ln2Ti3O10 for Ln=La, Nd, Sm, Gd, Dy separately and the photoactivity of K2Ln2Ti3O10 is strongly dependent on lanthanide, increasing in the sequence of La<Sm<Nd<Gd <Dy. A possible reason was put forward. 相似文献
109.
木工作用透射电子显微术及电子衍射技术研究3种PE(HDPE,LLDPE或LDPE)均聚物高取向薄膜的微结构。定量测定了它们的结晶尺寸。通过倾斜样品电子显微学研究确定了不同种PE纤维结构的对称性。 相似文献
110.