排序方式: 共有94条查询结果,搜索用时 15 毫秒
1.
应用格子Boltzmann三维模型,对双气泡在静水中的运动进行数值研究.采用八点差分和十八点差分格式分别求解一阶▽φ和二阶▽2φ可以有效避免气液密度比过大造成的数值不稳定问题.结果表明:当两个相同直径的气泡在上升时,位置靠上的气泡形状变化像单气泡上升一样,而位置靠下的气泡会受到前一个气泡尾迹的影响,并有很明显的形状变化.当两个气泡直径不同时,不管初始位置如何,大气泡总会对小气泡造成强烈的影响. 相似文献
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《中国化学快报》2023,34(6):107939
The water promotion effects, where water can provide a solution-mediated reaction pathway in various heterogeneous chemical catalysis, have been presented and attracted wide attention recently, yet, the rational design of catalysts with a certain ability of enhancing water-induced reaction process is full of challenges and difficulties. Here, we show that by incorporating alkali (Na, K) cations as an electronic and/or structural promoter into Pd/rGO-ZnCr2O4 (rGO, reduced graphene oxide), the obtained Pd(Na)/rGO-ZnCr2O4 as a representative example demonstrates an outstanding benzyl alcohol oxidation activity in the Pickering emulsion system in comparison to the alkali-free counterpart. The response experiments of water injection confirm the enhanced activity, and the Na-modified catalyst can further enhance the promotion effects of water on the reaction. The effects of alkali cations for Pd nanoparticles are identified and deciphered by a series of experimental characterizations (XPS, in situ CO-DRIFTS, and CO-TPR coupled with MS), showing that there is abundant −OH on the surface of the catalyst, which is stabilized by the formation of Pd−OHx. The alkali-stabilized Pd−OHx is helpful to enhance the water-induced reaction process. According to the results of in situ Raman as well as UV-vis absorption spectra, the Na-modulated Pd(Na)/rGO-ZnCr2O4 enables the beneficial characteristics for distorting the benzyl alcohol structure and enhancing the adsorption of benzyl alcohol. Further, the mechanism for enhanced water promotion effects is rationally proposed. The strategy of alkali cations-modified catalysts can provide a new direction to effectively enhance the chemical reaction involving small molecule water. 相似文献
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为建设适应新时代要求,突出高阶性、创新性、挑战度的一流本科课程,实现价值引领、能力培养和知识传授的教育教学目标,结合功能材料专业的特点和民族高等院校学生的学情,构建了物理化学基础课程的“四模块、三阶段、两时空、双平台”的混合式教学新模式,重塑了“价值引领模块、基础理论模块、多学科融合模块和虚拟仿真实验模块”的“四模块”内容体系。通过“四模块”嵌入下的混合式教学实践研究,结合学生的课前、课中、课后等学习成绩,多维度评价学习效果,并藉由调查问卷来分析学生对混合式教学的评价,最终研究结果表明学生的个性化自主学习能力有了显著提高、学生运用物理化学理论解决复杂问题的综合能力得到了提升,学生经过刻苦学习获得了素质提高的成就感。 相似文献
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Hongmei Liu Wenshu Zhou Shuyan Ding 《Journal of Difference Equations and Applications》2017,23(7):1204-1218
By computing the derivatives of five classical hypergeometric summation theorems, and applying the related properties of the digamma function, we derive a large number of closed summation formulae for generalized harmonic numbers. 相似文献
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大气压下介质阻挡放电应用领域具有多范畴、深广度、常态化等优势,针对同轴电极放电试验进行了系列参数诊断。采用自主研发的介质阻挡放电助燃激励器,在一个标准大气压、放电频率11.4 kHz、放电峰值电压5.4~13.4 kV(间隔1.0 kV)条件下进行了氩气电离试验。采用原子发射光谱法(AES)对氩等离子体谱线的激发、分光进行了检测分析;选用二谱线法及Boltzmann法测试了电子激励温度;根据Stark展宽效应计算了电子密度;获得了电子激励温度及电子密度随放电峰值电压增长的变化规律。结果表明,在试验电压条件下电子激励温度并不随外加电压的升高而递增,这表明通道内微放电的主要特征并不依赖于外部电压的供给,而是取决于气体组份、气体压强和放电模型,增大外加放电电压仅增加单位时间内微放电的数量,经整合电子激励温度可达3 500 K符合典型的低温等离子体特征;电子密度随外加电压的增长而趋于准线性趋势,电子密度数量级可达到108~109 cm-3,电离度偏弱。这些参数的探索对等离子体研讨有重大意义。 相似文献
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The improvement of gas-sensing properties of SnO<Subscript>2</Subscript>/zeolite-assembled composite
Yanhui?Sun Jing?WangEmail author Xiaogan?LiEmail author Haiying?Du Qingpan?Huang 《Journal of nanoparticle research》2018,20(5):134
SnO2-impregnated zeolite composites were used as gas-sensing materials to improve the sensitivity and selectivity of the metal oxide-based resistive-type gas sensors. Nanocrystalline MFI type zeolite (ZSM-5) was prepared by hydrothermal synthesis. Highly dispersive SnO2 nanoparticles were then successfully assembled on the surface of the ZSM-5 nanoparticles by using the impregnation methods. The SnO2 nanoparticles are nearly spherical with the particle size of ~?10 nm. An enhanced formaldehyde sensing of as-synthesized SnO2-ZSM-5-based sensor was observed whereas a suppression on the sensor response to other volatile organic vapors (VOCs) such as acetone, ethanol, and methanol was noticed. The possible reasons for this contrary observation were proposed to be related to the amount of the produced water vapor during the sensing reactions assisted by the ZSM-5 nanoparticles. This provides a possible new strategy to improve the selectivity of the gas sensors. The effect of the humidity on the sensor response to formaldehyde was investigated and it was found the higher humidity would decrease the sensor response. A coating layer of the ZSM-5 nanoparticles on top of the SnO2-ZSM-5-sensing film was thus applied to further improve the sensitivity and selectivity of the sensor through the strong adsorption ability to polar gases and the “filtering effect” by the pores of ZSM-5. 相似文献
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本文推广Vogt定理到广义n-赋范空间,即证明了两个广义n-赋范空间之间的保持ρ-诱导距离映射是仿射的. 相似文献
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According to classification of the matrix Lie algebras, a type of explicit Lie algebras are constructed which can be decomposed into a few Lie subalgebras. These subalgebras constitute several coupling commutator pairs from which some continuous multi-integrable couplings could be generated if the proper isospectral Lax pairs could be set up. Then the above Lie algebras are again decomposed into a kind of Lie algebras which are also closed under the matrix multiplication. From such the Lie algebras, some discrete multi-integrable couplings could be worked out. Finally, a few examples are given. However, the Hamiltonian structures of the (continuous and discrete) integrable couplings obtained by the above Lie algebras cannot be computed by using the trace identity or the quadratic-form identity, which is a strange and interesting problem. The phenomenon indicates that the importance of the Lie-algebra classification. The problem also needs us to try to find an efficient scheme to deal with. 相似文献
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《Tetrahedron》2014,70(21):3466-3470
An iron-catalyzed alkoxycarbonylation/cyclization reaction of N-arylacrylamides with carbazates has been developed. This new alkene difunctionalization reaction provides an efficient and straightforward method to obtain various ester-containing oxindoles. 相似文献