具有n个小时滞脉冲系统的周期解

本文考虑有n个小时滞的脉冲系统,利用隐函数存在性定理证明了该系统时滞 充分小时,系统的周期解存在性,推广了已有的相关结论.     

一类新的关于(4+4+1)-体共轭套中心构型

本文研究R3中一类(4+4+1)-体中心构型.利用中心构型等价类的性质及代数、分析方法,得到了该构型构成中心构型的充分和必要条件,证明了对任意给定的质量比这类中心构型存在的结论,解决了给定不同质量比范围该类中心构型是否唯一的问题,推广了文[16]的结论.     

预热处理对褐煤热解过程氧元素迁移的影响

以中国呼伦贝尔褐煤为原料,基于工业分析、元素分析、傅里叶变换红外光谱、气相色谱-质谱联用分析,考察140-230℃预热处理对褐煤650℃等温热解氧迁移的影响。结果表明,与未经预热处理的干煤热解相比,褐煤经200℃预热处理后热解,迁移至热解水和半焦中的氧分别下降7.55%和1.43%,迁移至焦油和气体中的氧分别增加6.66%和1.61%,焦油中酚类氧增加一倍。褐煤预热过程中氢键的减少与热解焦油中正己烷可溶物所含酚类化合物的增加,经原位红外漫反射光谱分析,发现源自OH…π、OH…N和羟基自缔合氢键在预热过程中断裂形成自由OH·,导致酚类化合物中苯酚和甲酚含量增加。     

泡沫镍上电沉积花瓣状NiFeOxHy/rGO用于析氧反应

开发碱性体系的高效低成本析氧电催化剂是由可再生能源转化制氢的关键。本研究通过在泡沫Ni基底上原位电化学沉积的方法制备了花瓣状NiFeO_xH_y和NiFeO_xH_y/rGO复合催化剂用于析氧反应。花瓣状的结构不仅明显提高了催化剂的比表面积,而且暴露了更多的层状边缘和缺陷,进而增加了催化剂的活性中心。还原氧化石墨烯的加入进一步提升了催化剂的电导和析氧电催化性能,通过优化NiFeO_xH_y/rGO在1 mol/L KOH溶液中的析氧性能为：过电位200 mV（10 mA/cm²）、Tafel斜率29.11 mV/decade,并且保持了较好的稳定性。     

气相色谱法分离正己烷和环己烷的实验设计与教学探索

The experiment of separating low toxic n-hexane and cyclohexane by traditional gas chromatography was improved with orthogonal experimental design. The effect of sample quantity, vaporization chamber temperature, detector temperature, column temperature, line velocity and separability of the split ratio were examined. Through the experiment, students could understand the use and maintenance of gas chromatography instruments. At the same time, they could understand separability and column efficiency of chromatography.     

ZnO纳米棒阵列到纳米管结构的自转化机制及其在相变封装材料中的应用

In the emerging field of nanoscience, tubular structures have been attracting remarkable interest due to their well-defined geometry, high specific area, and exceptional physical and chemical properties. Among them, oriented ZnO tubular arrays are regarded as promising candidates for various applications such as optoelectronics, solar cells, sensors, field emission, piezoelectrics, and catalysis. Although template-directed and selective dissolution synthesizing strategies are commonly used to prepare ZnO nanotubes, repeatability and large scale preparation are still challenging. In this study, ZnO nanotube arrays were controllably prepared by tuning the hydrothermal parameters, without the use of any additives. The mechanism underlying the self-conversion of ZnO nanorods to nanotubes was comprehensively studied based on the surface energy theory. It has been proved that the metastable top surface of the ZnO nanorods dissolves preferentially to reach a stable state during the hydrothermal growth. The specific surface energy of different crystal faces of ZnO nanorods was calculated using molecular dynamics simulation. The top surface of the ZnO nanorod, the Zn-terminated [0001] face, demonstrated much higher surface free energy than did the lateral faces, which indicated that the self-dissolution of top face (002) is energetically favorable. The self-conversion behavior of ZnO nanorod arrays with different diameters was specifically investigated by adjusting the initial precursor concentration, density of the crystal seed layers, and growth time. The dissolution-crystallization equilibrium concentration, determined by crystal surface energy, was found to be a key factor for the formation of the tubular structure. Notably, the critical equilibrium conditions for the self-conversion of ZnO nanorods to nanotubes, including zinc ion concentration and pH, have been identified by studying parameters corresponding to the dissolution-crystallization equilibrium for the metastable top surface of the ZnO nanorods. The preparation of the ZnO nanotube arrays was successfully accelerated and simplified via two-step procedure: (1) preparation of ZnO nanorod arrays and (2) self-conversion of ZnO nanorods to nanotubes. The preparation method based on the self-conversion mechanism from rods to tubes for polar oxides is simpler and more easily controllable as compared to the reported methods involving variety of additives. Because of the advantages of adaptability to a wide range of substrates, excellent conducting properties, and filling ability, the prepared ZnO nanotube array films were used in encapsulating phase-change materials. The encapsulated phase-change material exhibited excellent heat storage/release properties and heat conductivities. This indicates the potential application of precision devices for temperature control.     

两个包含联苯类三羧酸配体的钴(Ⅱ)和镍(Ⅱ)配位聚合物的合成、晶体结构及磁性质

采用水热方法,用2种联苯类三羧酸配体:联苯-2,4,4′-三羧酸(H3btc)、5-(3,4-二羧基苯基)吡啶甲酸(H_3dppa)和4,4′-联吡啶(4,4′-bipy)分别与CoCl_2·6H_2O和NiCl_2·6H_2O反应,合成了具有一维双螺旋链结构的配合物[Co(μ_2-H_2btc)2(4,4′-bipy)_2]_n(1)以及二维层状配位聚合物{[Ni_3(μ4-dppa)_2(H_2O)_6]·2H_2O}n(2),并对其结构和磁性质进行了研究。结构分析结果表明2个配合物都属于三斜晶系,P1空间群。配合物1具有一维双螺旋链结构,而且这些链通过O-H…O/N氢键作用进一步形成了三维超分子框架。而配合物2具有基于一维链单元的二维层状结构。4,4′-联吡啶在配合物1和2中分别起配位作用和模板作用。研究表明,配合物1中相邻钴离子间存在铁磁相互作用。     

两个基于刚性线型三羧酸配体的镍(Ⅱ)配合物的合成

采用水热方法,选用刚性线型三羧酸配体(H3L)和2,2′-联吡啶(2,2′-bipy)与NiCl2·6H2O分别在120和160℃温度下反应,得到了一个具有零维双核镍结构的配合物[Ni2(μ-HL)2(2,2′-bipy)2(H2O)4]·6H2O (1)和一个一维链状配位聚合物{[Ni(μ-HL)(2,2′-bipy)(H2O)2]·H2O}n(2),并对其结构和磁性质进行了研究。结构分析结果表明2个配合物均属于三斜晶系,P1空间群。配合物1具有零维双核镍结构,而且这些双核镍单元通过O-H…O/N氢键作用进一步形成了三维超分子框架,而配合物2具有一维链结构。2个配合物的结构差异可能是由于水热反应温度不同造成的。研究表明,配合物2中相邻镍离子间存在反铁磁相互作用。     

相变微胶囊型吸热剂MPCM-2的制备及其控热效果

以十二水合磷酸氢二钠为芯材,乙基纤维素为壁材,采用原位聚合工艺制备了相变微胶囊型吸热剂MPCM-2,其结构和性能经IR、 DSC、TG和粒度分析表征。结果表明：MPCM-2的相变温度为43.34和58.77 ℃,总相变焓值为144.82 J·g^-1,包裹率为67.5%; MPCM颗粒中径为57.26 μm,同时,MPCM-2应用于深水固井水泥浆体系可实现对水化热及水化温升的有效控制。     

3位间接连接有叔胺(仲胺)氮原子的3-季碳氧化吲哚化合物的合成

以3-卤氧化吲哚为起始原料,1,8-二氮杂二环十一碳-7-烯为催化剂,在二氯甲烷中与1-甲基吲哚经取代反应,或在甲苯溶液中于120 ℃条件下与吲哚（吲哚苯环上可连接有取代基）直接发生取代反应,合成了7个3位间接连接有叔胺（仲胺）氮原子的3-季碳氧化吲哚化合物,收率分别为80%~89%和 53%~70%,其结构经¹H NMR, ¹³C NMR和HR-MS（ESI-TOF）表征。