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当我们在阳光下洗衣服时,盆里的肥皂或洗衣粉泡上会出现各种彩色花纹,并且随泡的大小变化,花纹的形状和颜色也不断的变化;炎热的夏天,雨过天晴,柏油路的积水面上浮着一层油膜会呈现出五颜六色;用手把两片无色透明的玻璃片捏在一起,阳光下也能看到彩色花纹.以上现象的产生,是因为光产生了薄膜干涉现象。 相似文献
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结合高中新课程教科书,设计高中化学探究性实验——含磷洗衣粉对水藻生长的影响,通过实验原理、方法和具体实验过程得出结论,有效地促进了学生对化学知识的理解和掌握,培养学生实验设计和探究能力,达到知识、能力、情意目标。 相似文献
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Design of Phosphor-Free Single-Chip White Light-Emitting Diodes Using InAlGaN Irregular Multiple Quantum Well Structures 下载免费PDF全文
A novel approach for the design of phosphor-free single-chip white light-emitting diodes (LEDs) is proposed by employing InAIGaN irregular multiple quantum well (IMQW) structures. The electronic and optical properties of the designed InA1GaN IMQWs are analyzed in detail by fully considering the effects of strain, well-coupling, valence band-mixing, and quasi-bound states using the effective-mass Hamiltonian deduced from k. p theory. For comparison, three different types of InAIGaN IMQW structures with ultra-wide band spontaneous emission spectra are analyzed, and the results show that phosphor-free single-chip white light LEDs with more than 20Ohm emission band can be obtained using properly designed InAIGaN IMQW structures. 相似文献
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氮配位的无磷聚合物负载钯配合物对Suzuki反应的催化性能 总被引:2,自引:0,他引:2
制备了结构简单、氮配位的无磷钯配合物聚氯乙烯-二乙烯三胺钯, 利用XPS, TG, DTA和TEM等手段对其进行了表征. 热分析表明PVC-DETA-Pd在室温至220 ℃范围内有很好的热稳定性; TEM分析证实, 钯在PVC-DETA-Pd中分布比较均匀, 钯颗粒呈球形, 粒径在15 nm左右, 并测定了在不同温度、时间、溶剂和底物等条件下对Suzuki反应的催化性能及重复使用性能. 结果表明, 在没有惰性气体保护的情况下, 以NaHCO3作碱, 以DMF水溶液(体积比为2∶1)作溶剂, 在90 ℃时, 该配合物不仅对活性较高的碘代苯能够定量地催化, 对未活化的溴代苯也能定量地催化, 并且催化剂能够回收再利用8次以上. 相似文献
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This paper presents an experimental and numerical study of the packing, compression, and caking behaviour of spray dried detergent(SDD) powders with a two-fold aim: an experimental process of observation and evaluation of the packing, compression and caking behaviour of SDD powders, and a numerical approach based on discrete element modelling(DEM). The mechanical properties, including the stress–strain response and the corresponding porosity change as a function of consolidation stress in a confined cylinder, the stress–strain response during unconfined shearing and the cake strength as a function of consolidation stress, were evaluated and compared for different SDD powders using an extended uniaxial tester(Edinburgh Powder Tester – EPT). The experiments using EPT showed excellent reproducibility in the measurement of packing, compression and caking behaviour and were therefore very useful for describing the handling characteristics of these powdered products including screening new products and different formulations. It was found that the sample with higher moisture had lower bulk porosity but higher compressibility and cake strength. The porosity, compressibility and cake strength were found to vary across different size fractions of the same sample. The larger sieve-cut samples had higher initial bulk porosity, compressibility and cake strength. It is revealed that moisture plays a significant role in packing, compression, and shearing behaviour of the powder. Three-dimensional DEM modelling using a recently developed elasto-plastic adhesive-frictional contact model showed that the contact model is able to capture the detergent behaviour reasonably well and can be used to model complex processes involving these powders. 相似文献
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端视等离子体原子发射光谱法测定无磷洗衣粉中磷 总被引:3,自引:0,他引:3
利用端视等离子体原子发射光谱法测定了无磷洗衣粉的磷标准样品,探讨了基体元素钠对磷的干扰情况,对试验条件进行了优化,检出限为0.007μg·ml-1,RSD为2.9%~3.7%。方法简便快速,结果满意。 相似文献
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“无卤无磷无铅”的绿色阻燃环氧树脂基电子材料是既能满足阻燃功能、又需符合环保要求的热固性(复合)材料,是目前阻燃热固性树脂领域的重点和难点课题。有机氮杂环作为一类高效、低毒的阻燃结构,可以共价引入至环氧树脂中,但至今还未建立系统的氮杂环的结构与其阻燃性能的关系。本文结合本课题组近十年的研究工作,综述了近年来国内外含氮杂环阻燃环氧树脂的研究进展,讨论了不同含氮杂环结构(三嗪环、异氰脲酸酯环、二氮杂萘酮、酰亚胺、苯并 NFDA1 嗪和海因环等)环氧树脂固化物的制备方法,给出了定量的结构与性能关系。利用共价键法将含氮杂环结构引入环氧树脂体系中,在实现阻燃功能的同时也能保持材料的综合性能,甚至可提高环氧树脂固化物的热稳定性能,因而制备含氮杂环结构的环氧树脂是“无卤无磷无铅”绿色阻燃的重要解决方案。但是,目前仅依靠含氮杂环结构很难达到理想阻燃效果,大部分已报道的体系只能达到 “无卤无铅少磷”的水平,仍需要进一步深入研究和认识含氮杂环结构的阻燃环氧体系的结构-性能关系,并提出提高含氮杂环体系阻燃效果可能的解决方法。 相似文献