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表面物理化学性质对不同晶型MnO_2的NH_3-SCR活性影响(英文) 被引量:12
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作者 公丕军 谢峻林 +4 位作者 方德 韩达 何峰 李凤祥 齐凯 《Chinese Journal of Catalysis》 CSCD 北大核心 2017年第11期1925-1934,共10页
氮氧化物(NO_x)是主要的大气污染物之一,给环境和人类健康带来巨大危害.NH_3选择性催化还原(NH_3-SCR)技术是处理氮氧化物最有效的方法之一,现已被广泛用于氮氧化物的处理,其中SCR催化剂是该技术的核心.锰基催化剂具有相对较好的低温催... 氮氧化物(NO_x)是主要的大气污染物之一,给环境和人类健康带来巨大危害.NH_3选择性催化还原(NH_3-SCR)技术是处理氮氧化物最有效的方法之一,现已被广泛用于氮氧化物的处理,其中SCR催化剂是该技术的核心.锰基催化剂具有相对较好的低温催化活性,而其中MnO_2的催化活性最为突出.二氧化锰可以形成多种晶型,如α,β,δ和γ.晶相结构可显著影响催化活性,不同晶型的MnO_2具有不同的催化性能,其在电化学催化和CO催化方面已经得到广泛应用和研究.然而对于不同晶型MnO_2的NH_3低温选择催化还原NO_x的催化活性和催化机理的研究特别少.α-,β-,γ-和δ-MnO_2具有不同的晶型尺寸,并在气体吸附、气体扩散和催化反应过程中表现出较大差异.因此,有必要揭示不同MnO_2晶型表面物理化学性质与SCR催化活性之间的关系.本文成功制备出四种不同晶型的纳米MnO_2(α,β,δ和γ型)催化剂,并测试了其NH_3低温选择催化活性.此外,对催化剂进行了XRD,SEM,Raman,TG,BET,NH_3-TPD,XPS和H_2-TPR等一系列测试表征,探究了导致不同晶型MnO_2的NH_3催化还原NO_x差异的主要原因.结果表明,四种不同晶型纳米MnO_2的NH_3-SCR催化活性顺序为γ-MnO_2>α-MnO_2>δ-MnO_2>β-MnO_2.γ-MnO_2和α-MnO_2上的NO_x转化率在140–200°C范围内可达90%以上,但β-MnO_2在200°C只有40%的NO_x转化率.分析表明,γ-MnO_2和α-MnO_2的纳米线形貌具有较好的分散性,导致它们的比表面积较高,这为活性位点提供了更多的分散空间,有利于活性气体分子的吸附和催化过程的进行.H_2-TPR和NH_3-TPD结果显示,γ-MnO_2和α-MnO_2比其他两种晶型的MnO_2催化剂具有较好的可还原性和更多更强的酸性位点.XPS分析结果表明,在γ-MnO_2和α-MnO_2表面存在更多的化学吸附氧.基于上述这些有利的物理化学性质,γ-MnO_2和α-MnO_2催化剂显示出较好的低温NH_3-SCR活性.尽管δ-MnO_2的比表面积较小,但是NH_3-TPD结果显示其层状形貌的纳米晶体表面分散有较多的酸性位点,从而有效提升了其催化效果,同时其较好的氧化还原性能也有助于催化性能的改善. 展开更多
关键词 MNO2 晶体结构 表面活性氧 选择催化还原 物理化学性质
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基于Cholesky矩阵分解的贝叶斯压缩感知信号处理
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作者 笪涵 胡圣波 《贵州师范大学学报(自然科学版)》 CAS 2021年第1期72-76,共5页
随着雷达、卫星遥感技术的的高速发展,信号重构精度和效率的要求越来越高。针对传统贝叶斯压缩感知(Bayesian compressed sensing,BCS)算法需要进行高维矩阵反复求逆致使算法复杂度过高、运算时间过长的问题,结合Cholesky矩阵分解快速... 随着雷达、卫星遥感技术的的高速发展,信号重构精度和效率的要求越来越高。针对传统贝叶斯压缩感知(Bayesian compressed sensing,BCS)算法需要进行高维矩阵反复求逆致使算法复杂度过高、运算时间过长的问题,结合Cholesky矩阵分解快速求逆方法,提出一种基于矩阵分解的改进贝叶斯压缩感知算法。通过仿真比较传统的BCS算法、最小l 1范数算法和正交匹配追踪算法(OMP),笔者改进的BCS算法在不损失信号重构精度的同时大幅缩减了算法运算时间,重构效果得到改善。 展开更多
关键词 信号重构 贝叶斯压缩感知 复杂度 Cholesky矩阵分解
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Nucleic acids analysis 被引量:1
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作者 Yongxi Zhao Xiaolei Zuo +41 位作者 Qian Li Feng Chen Yan-Ru Chen Jinqi Deng da han Changlong Hao Fujian Huang Yanyi Huang Guoliang Ke Hua Kuang Fan Li Jiang Li Min Li Na Li Zhenyu Lin Dingbin Liu Juewen Liu Libing Liu Xiaoguo Liu Chunhua Lu Fang Luo Xiuhai Mao Jiashu Sun Bo Tang Fei Wang Jianbin Wang Lihua Wang Shu Wang Lingling Wu Zai-Sheng Wu Fan Xia Chuanlai Xu Yang Yang Bi-Feng Yuan Quan Yuan Chao Zhang Zhi Zhu Chaoyong Yang Xiao-Bing Zhang Huanghao Yang Weihong Tan Chunhai Fan 《Science China Chemistry》 SCIE EI CAS CSCD 2021年第2期171-203,共33页
Nucleic acids are natural biopolymers of nucleotides that store, encode, transmit and express genetic information, which play central roles in diverse cellular events and diseases in living things. The analysis of nuc... Nucleic acids are natural biopolymers of nucleotides that store, encode, transmit and express genetic information, which play central roles in diverse cellular events and diseases in living things. The analysis of nucleic acids and nucleic acids-based analysis have been widely applied in biological studies, clinical diagnosis, environmental analysis, food safety and forensic analysis.During the past decades, the field of nucleic acids analysis has been rapidly advancing with many technological breakthroughs.In this review, we focus on the methods developed for analyzing nucleic acids, nucleic acids-based analysis, device for nucleic acids analysis, and applications of nucleic acids analysis. The representative strategies for the development of new nucleic acids analysis in this field are summarized, and key advantages and possible limitations are discussed. Finally, a brief perspective on existing challenges and further research development is provided. 展开更多
关键词 nucleic acids analysis signal amplification DNA nanotechnology APTAMER BIOSENSING
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Covalent stabilization of DNA nanostructures on cell membranes for efficient surface receptor-mediated labeling and function regulations
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作者 dandan Chao Xuemei Xu +7 位作者 Yanyan Miao Linlin Yang Qianqian Gao Rui Xu Yuan Tian Yumeng Zhao Yuzhen Du da han 《Science China Chemistry》 SCIE EI CAS CSCD 2022年第11期2327-2334,共8页
One major challenge of using DNA nanostructures for cellular and in vivo applications is their insufficiently structural integrity that stems from the non-covalent base pairing and stacking in complex cellular and phy... One major challenge of using DNA nanostructures for cellular and in vivo applications is their insufficiently structural integrity that stems from the non-covalent base pairing and stacking in complex cellular and physiological environment. The establishment of covalent bonds in DNA nanostructures can link individual strands more stably and therefore should improve the performance of DNA nanostructures in different scenarios where structural integrity is required. Here, we developed a convenient and effective method for constructing covalently stabilized DNA nanostructures by chemically inserting photo-crosslinker(^(CNV)K) in DNA sequences. These covalently linked DNA nanostructures were found to be more resistant to external interference, such as low cation concentrations and unspecific displacement on cell membranes. We also demonstrated that our strategy could improve the efficiency of cell surface receptor-mediated labeling and function regulations in living cells, which sheds light on broadening the biomedical applications of DNA nanostructures. 展开更多
关键词 DNA nanostructures covalent stabilization structural integrity cell labeling surface receptor regulation
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