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纳米颗粒悬浮液池内泡状沸腾的实验研究 总被引:7,自引:0,他引:7
本文对纳米颗粒悬浮液在平壁面上池内沸腾进行了实验研究。实验用的纳米粒子为26 nm的铁粉和13 nm的三氧化二铝纳米粉末,基液为去离子水。分别配成体积浓度为0.1%, 1%和2%的悬浮液。实验结果表明,纳米悬浮颗粒对液体沸腾换热过程的影响会随着纳米颗粒性质,颗粒浓度及热流密度大小的不同而出现不同的效果;加入纳米颗粒后, 对基液沸腾换热的影响存在着两个相反的作用机制,它们分别为:纳米颗粒增强了液体内部的热量迁移能力(热物性的影响)和改变了加热面的表面结构特性(加热面特性的影响)。 相似文献
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光学活性化合物的工业合成 总被引:9,自引:0,他引:9
本文介绍了光学活性化合物研究现状及发展趋势。并从技术和经济角度论述了工业合成光学活性化合物的可能性 相似文献
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Measurement of labile Cu in soil using stable isotope dilution and isotope ratio analysis by ICP-MS 总被引:1,自引:0,他引:1
Isotope dilution is a useful technique to measure the labile metal pool, which is the amount of metal in soil in rapid equilibrium (<7 days) with the soil solution. This is normally performed by equilibrating soil with a metal isotope, and sampling the labile metal pool by using an extraction (E value), or by growing plants (L value). For Cu, this procedure is problematic for E values, and impossible for L values, due to the short half-life of the 64Cu radioisotope (12.4 h), which makes access and handling very difficult. We therefore developed a technique using enriched 65Cu stable isotope and measurement of 63Cu/65Cu ratios by quadrupole inductively coupled plasma mass spectrometry (ICP-MS) to measure labile pools of Cu in soils using E value techniques. Mass spectral interferences in detection of 63Cu/65Cu ratios in soil extracts were found to be minimal. Isotope ratios determined by quadrupole ICP-MS compared well to those determined by high-resolution (magnetic sector) ICP-MS. E values determined using the stable isotope technique compared well to those determined using the radioisotope for both uncontaminated and Cu-contaminated soils. 相似文献
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Markus Bergauer 《Tetrahedron》2004,60(5):1197-1204
Chemo- and regioselective transformations of asparagine gave access to optically active 5- and 6-amino tetrahydroindolizines when the 3-aminobutyrolactone (S)-2 was employed as a key intermediate. The target compounds were approached by a sequential and regiocontrolled bis-electrophilic attack in the positions 2 and 3 of the pyrrole ring system. Receptor binding experiments showed stereocontrolled receptor recognition leading to the D3 selective agonist (S)-8 with D3 binding that is comparable to the natural neurotransmitter dopamine. 相似文献
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The first stereoselective syntheses of the naturally occurring, ,β-unsaturated lactone hyptolide 1 and of its nonnatural epimer at C-6 are described. Ethyl l-lactate was the chiral starting material. Key steps of these syntheses were a Brown's asymmetric allylation, a Carreira's asymmetric ethynylation and a ring closing metathesis. 相似文献
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Dr. Velayudham Ramadoss Yue Zheng Xiaoqing Shao Dr. Lifang Tian Prof. Yahui Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3213-3228
Owing to their non-toxic, stable, inexpensive properties, carboxylic acids are considered as environmentally benign alternatives as coupling partners in various organic transformations. Electrochemical mediated decarboxylation of carboxylic acid has emerged as a new and efficient methodology for the construction of carbon-carbon or carbon-heteroatom bonds. Compared with transition-metal catalysis and photoredox catalysis, electro-organic decarboxylative transformations are considered as a green and sustainable protocol due to the absence of chemical oxidants and strong bases. Further, it exhibits good tolerance with various functional groups. In this Minireview, we summarize the recent advances and discoveries on the electrochemical decarboxylative transformations on C−C and C−heteroatoms bond formations. 相似文献
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The effects of flooring materials on the combustion behavior of thermoplastics is investigated. Based on the ISO 9705 fire test setup, an experimental rig was designed. Full‐scale experiments of PP combustion were carried out using five flooring boards, namely gypsum, steel, wood, ceramic tile and PVC. The experimental results indicate that the flooring boards play an important role in the heat release rates of typical thermoplastics combustion. Specifically, the time for the sharp increase of heat release rate is generally later for the flooring boards with larger thermal conductivity, except for the case of PVC. Preliminary analyses suggest that the reason for the exception of PVC is the expansion and carbonization of PVC at high temperature. In addition, experimental results also show that the corresponding peak heat release rate of thermoplastics combustion would be generally smaller for the flooring board with a larger thermal mass, except for the case of gypsum. The primary cause for the exception of gypsum may be the heat absorption by the crystal water released from the gypsum during the burning of hot pool oil. 相似文献