排序方式: 共有131条查询结果,搜索用时 15 毫秒
31.
以间苯三酚为起始原料,在伊顿试剂的催化作用下,与不同取代水杨酸反应合成1,3-二羟基呫吨酮类化合物3a~3l 12个,收率63%~87%,并探讨了反应机理及结构-反应活性关系.利用紫外分光光度法测定了所合成化合物对亚硝酸盐的清除作用,结果表明,在37℃、pH 3及反应时间为30 min条件下,1,3-呫吨酮类化合物对亚硝酸根均有较好的清除作用,其中化合物3f和3b的清除作用最强,清除率达34%.同时对1,3-二羟基呫吨酮类化合物清除亚硝酸盐的作用机制及构效关系进行了探讨. 相似文献
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Impaction of spray droplets on leaves: influence of formulation and leaf character on shatter,bounce and adhesion 总被引:5,自引:0,他引:5
Gary J. Dorr Shuangshuang Wang Lisa C. Mayo Scott W. McCue W. Alison Forster Jim Hanan Xiongkui He 《Experiments in fluids》2015,56(7):143
This paper combines experimental data with simple mathematical models to investigate the influence of spray formulation type and leaf character (wettability) on shatter, bounce and adhesion of droplets impacting with cotton, rice and wheat leaves. Impaction criteria that allow for different angles of the leaf surface and the droplet impact trajectory are presented; their predictions are based on whether combinations of droplet size and velocity lie above or below bounce and shatter boundaries. In the experimental component, real leaves are used, with all their inherent natural variability. Further, commercial agricultural spray nozzles are employed, resulting in a range of droplet characteristics. Given this natural variability, there is broad agreement between the data and predictions. As predicted, the shatter of droplets was found to increase as droplet size and velocity increased, and the surface became harder to wet. Bouncing of droplets occurred most frequently on hard-to-wet surfaces with high-surface-tension mixtures. On the other hand, a number of small droplets with low impact velocity were observed to bounce when predicted to lie well within the adhering regime. We believe this discrepancy between the predictions and experimental data could be due to air layer effects that were not taken into account in the current bounce equations. Other discrepancies between experiment and theory are thought to be due to the current assumption of a dry impact surface, whereas, in practice, the leaf surfaces became increasingly covered with fluid throughout the spray test runs. 相似文献
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Two-stage thermoelectric generators have been widely used in the aerospace, military, industrial and daily life fields. Based on the established two-stage thermoelectric generator model, this paper further studies its performance. Applying the theory of finite-time thermodynamics, the efficient power expression of the two-stage thermoelectric generator is deduced firstly. The maximum efficient power is obtained secondly by optimizing the distribution of the heat exchanger area, distribution of thermoelectric elements and working current. Using the NSGA-II algorithm, multi-objective optimizations of the two-stage thermoelectric generator are performed thirdly by taking the dimensionless output power, thermal efficiency and dimensionless efficient power as objective functions, and taking the distribution of the heat exchanger area, distribution of thermoelectric elements and output current as optimization variables. The Pareto frontiers with the optimal solution set are obtained. The results show that when the total number of thermoelectric elements is increased from 40 to 100, the maximum efficient power is decreased from to . When the total heat exchanger area is increased from to , the maximum efficient power is increased from to . The deviation indexes are 0.1866, 0.1866 and 0.1815 with LINMAP, TOPSIS and Shannon entropy decision-making approaches, respectively, when multi-objective optimization is performed on three-objective optimization. The deviation indexes are 0.2140, 0.9429 and 0.1815 for three single-objective optimizations of maximum dimensionless output power, thermal efficiency and dimensionless efficient power, respectively. 相似文献
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以邻苯二酚与溴乙烷为原料、聚乙二醇为相转移催化剂合成邻苯二乙醚,再经过冰醋酸和硝酸硝化得到对硝基邻苯二乙醚。研究了反应温度、反应时间、原料摩尔比和催化剂用量等对反应收率的影响,获得了合成邻苯二乙醚的优化工艺条件:n(C6H4(OH)2)∶n(NaO H)∶n(C2H5Br)=1∶2.6∶2.4,反应温度80℃,反应时间4h,催化剂用量2g,该反应条件下邻苯二乙醚平均收率88%。混酸硝化条件下合成对硝基邻苯二乙醚的较佳工艺条件为n(C10H14O2)∶n(HNO3)=1∶1.2,乙酸25mL,反应时间30min,反应温度20℃,该反应条件下对硝基邻苯二乙醚平均收率为99%。 相似文献
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Selective solvent annealing induced phase separation and dewetting in PMMA/SAN blend ultrathin films
Shuangshuang Zhang Yu Zhu Tongfei Shi Hui Zhao Jichun You Yongjin Li 《Journal of Polymer Science.Polymer Physics》2014,52(19):1243-1251
Phase behaviors induced by solvent annealing in poly(methyl methacrylate) (PMMA) and poly(styrene‐ran‐acrylonitrile) (SAN) blend ultrathin films have been investigated by atomic force microscopy and grazing incidence small‐angle X‐ray scattering. Our results indicate that both the phase separation within the blend and the dewetting of the film induced by composition fluctuation take place upon the selective solvent annealing, producing complex structures containing upper droplets (of one phase) and mimic‐films (of the other rich‐phase). The use of acetic acid (the selective solvent for PMMA) generates PMMA mimic‐film and SAN droplets, while the introduction of DMF (exhibiting better solubility for SAN) vapor results in the formation of SAN mimic‐film and PMMA droplets. Essentially, the interaction at polymer/substrate interface, resultant wettability of selected component, solubility of PMMA and SAN in adopted solvent dominate not only the phase separation and the dewetting of the whole film but also the synergism of them. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1243–1251 相似文献
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He Ying Du Shuangshuang Li Huailong Cheng Qilin Pavlinek Vladimir Saha Petr 《Journal of Solid State Electrochemistry》2016,20(5):1459-1467
Journal of Solid State Electrochemistry - A facile two-step strategy is developed for synthesis of MnO2/polyaniline (PANI) hybrid nanostructures on carbon cloth (CC). Vertically aligned PANI... 相似文献
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Shuangshuang Fan Jianhua Yi Li Wang Zhentao Mi 《Reaction Kinetics and Catalysis Letters》2007,92(1):175-182
Pd/Al2O3 catalysts were prepared by the impregnation method and were used for the direct formation of hydrogen peroxide from H2 and O2. The H2O2 concentration and selectivity were strongly dependent on the solubility of hydrogen in the reaction medium. The modification
of the support by halogenate has a beneficial effect on the selectivity. The state of the active Pd on Pd/Al2O3 catalysts was studied using X-ray photoelectron spectroscopy, and Pd(0) was found to be active. 相似文献
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利用传输矩阵方法计算了铀同位素链$\alpha$ 衰变的穿透几率,并且与常用于计算势垒穿透几率的Wenzel Kramers Brillouin(WKB)近似方法进行了比较,发现由WKB近似方法得到的穿透几率比精确值小40%左右,而且WKB方法带来的误差与$\alpha$ 衰变的衰变能有很好的抛物线关系。基于结团模型,利用传输矩阵方法得到$\alpha$ 粒子穿透势垒的精确几率,计算了铀同位素链$\alpha$ 衰变的半衰期。还研究了势阱深度$V_0$ 、弥散宽度$a$ 和主量子数$G$ 对半衰期的影响。结果表明,考虑一组同位旋依赖的势阱深度和弥散宽度参数,结团模型能够较好地再现铀同位素链$\alpha$ 衰变的半衰期。 相似文献
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This article deals with the Fujita-type theorems to the Cauchy problem of degenerate parabolic equation not in divergence form with weighted source u t ?=?u p Δu?+?a(x)u q in ? n ?×?(0,?T), where p?≥?1, q?>?1, and the positive weight function a(x) is of the order |x| m with m?>??2. It was known that for the degenerate diffusion equation in divergence form, the weight function affects both of the critical Fujita exponent and the second critical exponent (describing the critical smallness of initial data required by global solutions via the decay rates of the initial data at space-infinity). Contrarily, it is interesting to prove that the weight function in the present model with degenerate diffusion not in divergence form influences the second critical exponent only, without changing the critical Fujita exponent. 相似文献