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1.
通过对523名高职学生进行实地调研,探析“学习参与度”对学生创新创业核心素养的影响机制。结果显示:课程建设、教师引导、资源支持对学习心理参与度影响显著;教师引导、资源支持、社会实践对学习行为参与度影响显著。学习参与度显著影响创业意识、创新精神、创业能力。提出优化对策:重视学生创新创业核心素养的培养;提高学生创新创业学习参与度;人际互动提升学习心理参与度;协同培育提高学习行为参与度。 相似文献
2.
Weiyi Li Geng Leng Caiqin Li Yajing Lyu 《International journal of quantum chemistry》2020,120(8):e26150
The mechanisms of CO2 coupling with the propargylic alcohol using alkali carbonates M2CO3 (M = Li, Na, K, Cs) have been investigated by means of density functional theory calculations. The calculations reveal that the target product tetronic acid (TA) is yielded through two stages: (a) the formation of the α-alkylidene cyclic carbonate (αACC) intermediate via Cs2CO3-mediated carboxylative cyclization of the propargylic alcohol with CO2, and (b) the conversion of the αACC intermediate with Cs2CO3 to produce the cesium salt of the TA. Since the overall kinetic barriers for the two stages are comparable and affordable, the excellent chemoselectivity to the TA should be primarily originated from the high thermodynamic stability of the cesium salt of the TA. Moreover, relative to the TA, the possibility to yield the by-product acyclic carbonate can be excluded due to the both kinetics and thermodynamic inferiority. This result is different from the organic base-mediated reaction. Alternatively, our calculations predict that CsHCO3 together generated with the cesium salt of the TA might also be an available mediating reagent for the incorporation of CO2 with the propargylic alcohol. Compared to other alkali carbonates M2CO3 (M = Li, Na, K), the stronger basicity of Cs2CO3 and the lower ionic potential of cesium ion can raise the effective concentration of the αACC intermediate, and thus the conversion of the αACC intermediate into the cesium salt of the TA can be achieved with high yield. 相似文献
3.
当前锂离子动力电池电化学模型存在模型复杂、建模难度大、计算效率低、老化评估效果差的问题,本文提出一种考虑电池衰退老化的机理模型(ADME).本文首先通过有限差分法对伪二维(P2D)电化学模型进行离散降阶处理,得到简化伪二维(SP2D)模型.在SP2D模型的基础上,基于阴阳两极发生的副反应导致的衰退老化现象,提出一种考虑电池衰退老化的机理模型.其次,使用多变量偏差补偿最小二乘法实现模型参数辨识.最后通过动力电池衰退老化性能循环实验,对比分析了恒流、脉冲工况下SP2D模型和ADME模型的终端电压输出.结果表明:ADME模型较为简单、计算效率和估算精度高,可以有效评估电池容量老化衰退,得到理想的锂离子动力电池外特性曲线. 相似文献
4.
5.
Simen Gjelseth Antonsen Arne Joakim C. Bunkan Tomas Mikoviny Yngve Stenstrøm Armin Wisthaler 《Molecular physics》2020,118(15)
The kinetics of the O3, OH and NO3 radical reactions with diazomethane were studied in smog chamber experiments employing long-path FTIR and PTR-ToF-MS detection. The rate coefficients were determined to be k CH2NN+O3?=?(3.2?±?0.4)?×?10?17 and k CH2NN+OH?=?(1.68?±?0.12)?×?10?10 cm3 molecule?1 s?1 at 295?±?3?K and 1013?±?30 hPa, whereas the CH2NN?+?NO3 reaction was too fast to be determined in the static smog chamber experiments. Formaldehyde was the sole product observed in all the reactions. The experimental results are supported by CCSD(T*)-F12a/aug-cc-pVTZ//M062X/aug-cc-pVTZ calculations showing the reactions to proceed exclusively via addition to the carbon atom. The atmospheric fate of diazomethane is discussed. 相似文献
6.
DFT mechanistic study of the H2‐assisted chain transfer copolymerization of propylene and p‐methylstyrene catalyzed by zirconocene complex
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Cheng‐Gen Zhang Shu‐Yuan Yu Liaoyun Zhang Huayi Li Zhi‐Xiang Wang 《Journal of polymer science. Part A, Polymer chemistry》2015,53(4):576-585
DFT computations have been performed to investigate the mechanism of H2‐assisted chain transfer strategy to functionalize polypropylene via Zr‐catalyzed copolymerization of propylene and p‐methylstyrene (pMS). The study unveils the following: (i) propylene prefers 1,2‐insertion over 2,1‐insertion both kinetically and thermodynamically, explaining the observed 1,2‐insertion regioselectivity for propylene insertion. (ii) The 2,1‐inserion of pMS is kinetically less favorable but thermodynamically more favorable than 1,2‐insertion. The observation of 2,1‐insertion pMS at the end of polymer chain is due to thermodynamic control and that the barrier difference between the two insertion modes become smaller as the chain length becomes longer. (iii) The pMS insertion results in much higher barriers for subsequent either propylene or pMS insertion, which causes deactivation of the catalytic system. (iv) Small H2 can react with the deactivated [Zr]?pMS?PPn facilely, which displace functionalized pMS?PPn chain and regenerate [Zr]? H active catalyst to continue copolymerization. The effects of counterions are also discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 576–585 相似文献
7.
《Comptes Rendus Chimie》2015,18(9):993-1000
The electrochemical oxidation of N-acetyl-p-aminophenol (PAR) was investigated at a Pt electrode with the application of cyclic (CV) and differential pulse (DPV) voltammetry methods. An effect of scan rate, substrate concentration and pH on electrode reactions was determined. The parameters of substrate electro-oxidation, i.e. heterogeneous rate constant, charge transfer coefficient, and diffusion coefficient, were calculated. Our investigation's results prove the exchange of two electrons and one proton in the first step, followed by a chemical reaction. PAR electro-oxidation occurs according to an EC mechanism. 相似文献
8.
针对多层织物织造过程中,各层纬纱打纬力需保持一致以及需要减少钢筘与纱线之间摩擦的要求,提出八连杆平行打纬机构,并根据工艺要求对打纬机构进行优化。以打纬机构的主轴转动140°时,筘座在后心位置处的近似静止位移Δs最小为优化目标,通过Matlab软件分析确定设计变量,优化钢筘在后死心位置的近似停留时间。运动学仿真结果表明,优化后的打纬机构不仅保证了钢筘的打纬动程和其在后死心处的静止时间,而且增大了钢筘的惯性打纬力,有利于厚重织物的打纬。 相似文献
9.
Alkynes cycloaddition reactions are powerful tools for constructing cyclic molecules with optimal atom efficiency, but these reactions cannot proceed at ambient temperature without transition-metal catalysts. In this work, a heterobimetallic complex featuring an Nb–Fe triple bond, Nb(iPrNPMe2)3Fe–PMe3, has been evaluated as the potential catalyst for acetylene cycloaddition, using density functional theory. The calculated results show that the singlet-state (i.e. ground-state) Nb(iPrNPMe2)3Fe–PMe3 can be applied to benzene synthesis, but is not suitable for cyclobutadiene. Benzene can be obtained easily at room temperature and is the unique product on the singlet potential surface. The irradiation of infrared-red light can drive the excitation of singlet Nb(iPrNPMe2)3Fe–PMe3 to its triplet state. Both benzene and cyclobutadiene can be formed on the triplet reaction potential surface due to their low energy barriers. Therefore, Nb(iPrNPMe2)3Fe–PMe3 is a potential high reactivity heterobimetallic catalyst for the cyclotrimerization of alkynes. In the reaction process, the catalytic active site of Nb(iPrNPMe2)3Fe–PMe3 moves from niobium to iron. 相似文献
10.
采用密度泛函理论B3LYP方法,研究了锡苯和铅苯的[2+2],[4+2]及[4+4]二聚反应的微观机理和势能剖面,考察了Sn(Pb)原子上的2,4,6-三甲基苯基(Mes)取代基对反应势能剖面的影响.研究结果表明,所有反应均为协同过程,且大多数情况下,2个C—Sn(Pb)键同步形成.[2+2]和[4+2]反应在热力学和动力学上均比相应的[4+4]反应容易进行,而[4+2]反应在动力学上比相应的[2+2]反应有利.Sn(Pb)原子上的Mes取代基在热力学和动力学上均不利于反应的进行.铅苯的动力学稳定性与锡苯相当,但其热力学稳定性高于锡苯. 相似文献