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Search Results: 1 - 10 of 24140 matches for " 潘黎明 "
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基于综合分析法的大采高综放采场来压特征研究
黎明
煤炭科学技术 , 2015,
Abstract:
羟基自由基引发的邻二甲苯大气氧化机理
The Atmospheric Oxidation Mechanism of o-Xylene Initiated by Hydroxyl Radicals

姗姗,黎明,()
- , 2015, DOI: 10.3866/PKU.WHXB201510152
Abstract: 采用量子化学、过渡态理论和单分子反应理论计算,研究了由羟基(OH)自由基引发的邻二甲苯(oX)大气氧化降解机理.在M06-2X/6-311++G(2df, 2p)水平上优化了反应物、过渡态和产物的结构,在ROCBSQB3水平上计算了反应势能面.采用过渡态理论计算了各个可能反应步骤的速率常数和反应通道的分支比,同时还采用单分子反应理论(RRKM-ME)计算探讨了反应的压力效应.计算发现,在大气中,邻二甲苯与OH的反应以苯环加成为主,首先形成两个加和物oX-1-OH (R1)和oX-3-OH (R3),它们随后与大气中的氧气发生反应.R1和R3与O2可直接发生不可逆直接夺氢生成二甲基苯酚,或和O2的可逆加成,生成双环自由基中间体.双环自由基将与大气中的氧气结合,形成双环过氧自由基,接着与NO或HO2反应生成有机硝酸酯或有机过氧化氢化合物,或被还原为双环烷氧自由基,并最终生成产物,包括丁二酮、丁烯二醛、甲基乙二醛、4-氧-2-戊烯醛、2, 3-环氧丁二醛以及少量的乙二醛.这些产物中有机过氧化氢和甲基乙二醛被认为对二次气溶胶有较大的贡献.结合理论计算和文献报道的实验结果,提出了新的oX大气氧化机理,预测了在高NO浓度条件下可能产物的分支比,并与文献报道结果相比较.最后还讨论了温度对反应机理的影响.
The atmospheric oxidation mechanism of o-xylene (oX) initiated by hydroxyl (OH) radicals has been investigated by using quantum chemistry, transition state theory, and unimolecular theory (RRKMME) calculations. Molecular structures of reactants, transition states, and products are optimized at M06-2X/6-311++G(2df, 2p) level, and the electronic energies are calculated at the ROCBS-QB3 level. The classical transition state theory is employed to predict the rates or rate constants for all the reaction steps as well as the branching ratios of the reaction pathways. RRKM-ME calculations are employed to explore the pressure-dependence of the reaction kinetics. Under atmospheric conditions, the oxidation of o-Xylene is dominated by OH addition to the C1 and C3 positions, forming adducts oX-1-OH (R1) and oX-3-OH (R3), which will readily react with atmospheric oxygen. The reactions of R1 and R3 with O2 can proceed by irreversible H-abstraction to dimethylphenols (R3 only), or by reversible addition to form bicyclic radicals, which recombine with atmospheric oxygen to form bicyclic peroxy radicals (BPRs). BPRs will react with NO and/or HO2 in the atmosphere, forming organonitrate, hydroperoxides (ROOH), and bicyclic alkoxy radicals (BARs), of which the BARs eventually transfer to the final products, including biacetyl, butenedial, methylglyoxal, 4-oxo-2-pentenal, epoxy-2, 3-butenedial, and a small amount of glyoxal. The products ROOH and methylglyoxal are considered to contribute to the formation of secondary organic aerosols. A new oxidation mechanism of oX in the atmosphere is proposed, based on the current theoretical predictions and previous experimental measurements, and the predicted product yields under high NO conditions are compared with previous experimental measurements. The effect of temperature on the oxidation mechanism is also discussed
?基于企业生命周期理论的企业绩效评价方法研究
??赵黎明,康宇
天津大学学报(社会科学版) , 2008,
Abstract: ?以企业生命周期理论为理论依据,设计了以主成分分析为主要工具的企业绩效评价方法,在不同生命周期假设下,对国内医药行业的17家股份有限公司2005年企业绩效进行了实证研究。该评价方法从企业监管者和投资者角度动态评价处于不同生命周期的企业的绩效,并且给出对17个企业绩效评价的综合排序。
青海湖北岸山地干草原植物群落多样性分析
黎明
草业科学 , 2010,
Abstract: ?通过对青海湖北岸山地干草原群落特征及物种多样性的分析,结果表明可将青海湖北岸芨芨草Achnatherumsplendens草地、弃耕地、山坡草地和零星分布芨芨草的草地划分为4种群落类型芨芨草+早熟禾Poasp.群落、早熟禾+垂穗披碱草Elymusnutans群落、艹洽草Koeleriacristatum+西北针茅Stipakrylovii群落和西北针茅+垂穗披碱草群落。植物多样性指数变化为ShannonWeiner指数和Simpson指数变化的大小顺序是滩地>山坡草地>弃耕地>芨芨草草地,Pielou均匀度指数变化的大小顺序为山坡草地>弃耕地>滩地>芨芨草草地,丰富度指数大小顺序为滩地>弃耕地>山坡草地>芨芨草草地。生境条件的差异导致了物种多样性的形成。
1995~1998召开的部分国际地学会议预告
黎明
地球科学进展 , 1995, DOI: 10.11867/j.issn.1001-8166.1995.03.0309
Abstract:
1991年7~12月部分地学会议预告
黎明
地球科学进展 , 1991, DOI: 10.11867/j.issn.1001-8166.1991.04.0094
Abstract:
1990年7—12月部分地学国际会议预告
黎明
地球科学进展 , 1990, DOI: 10.11867/j.issn.1001-8166.1990.03.0078
Abstract:
国际化地层委员会(ICS)及其未来的发展方向
黎明
地球科学进展 , 2001, DOI: 10.11867/j.issn.1001-8166.2001.04.0595
Abstract:
1988—1989年国际会议预告
黎明
地球科学进展 , 1988, DOI: 10.11867/j.issn.1001-8166.1988.03.0064
Abstract:
1994年召开的部分国际地学会议
黎明
地球科学进展 , 1994, DOI: 10.11867/j.issn.1001-8166.1994.02.0092
Abstract:
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