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利用X射线光电子能谱(XPS)、X射线衍射(XRD)及扩展的X射线精细结构谱(EXAFS)对氧化钴在二氧化钛表面的分散及结构进行了系统研究。结果表明:氧化钴能够在二氧化钛表面实现单层分散,其分散阈值为每平方纳米的二氧化钛分布1.4个钴原子。当负载量小于分散阈值时,钴以二价存在并形成分立的钴氧六配位[CoO6];而当负载量大于分散阈值时,晶体Co3O4在二氧化钛表面形成,钴以两种形式存在,即分散态的钴氧六配位[CoO4]和晶态的Co3O4。实验还表明二氧化钛对二价钴具有明显的稳定作用。 相似文献
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为解决风洞试验过程中可靠地、精确地控制半柔壁系统型面变化,必须使电动推杆多轴协调同步运动;以某连续式风洞半柔壁系统为例,采用西门子T-CPU和S120伺服单元搭建硬件系统,运用梯形或S形加速与减速方式,保证同启同停进行同步,并将实际位置值实时与理论计算值进行比对,协调同步运动电动推杆,从而精确控制半柔壁系统型面变化;试验结果表明,该方法能够实现半柔壁机构在运动中多轴协调同步,保证机构运行安全;该系统在国内风洞半柔壁控制领域尚属首例,理论方法高效且通用性较强可广泛用于使用任何品牌和型号伺服控制系统控制半柔或全柔系统。 相似文献
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氧化镁表面修饰稀土催化材料的制备和气敏性能 总被引:1,自引:0,他引:1
本文采用湿化学过程的柠檬酸络合法、可控化学沉淀法和溶胶-凝胶法合成了纳米复合金属氧化物LaFeO3,利用各种分析方法对材料的物性和结构进行了分析和表征;并测定了材料对氧化性气体和还原性气体的气敏性能.研究结果表明LaFeO3复合物对NO2在350℃灵敏度高达127.83,特别通过添加MgO对基材进行表面修饰灵敏度提高到845.37,约添加前的70倍.本文还进一步考察了添加质和添加量对基材的结构和气敏性能的影响,并通过研究材料表面对气体的吸脱附性能和元素电子结合能的变化对敏感作用机制进行了深入分析和探讨. 相似文献
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散斑噪声是激光干涉时的普遍现象,其覆盖被测表面对应区域的形状信息,造成测量误差。针对斜入式激光干涉测量中散斑噪声的特点,提出一种基于物体像的散斑噪声的识别方法。该方法通过统计物体像中有效测量区域和背景区域内灰度分布的特点,自动计算出判定散斑噪声的上下阈值。基于物体像与干涉条纹图像间微米级的映射关系,得到干涉条纹图像中散斑噪声的位置。设计了相关实验,对干涉条纹图像中识别出的散斑噪声区域进行修补,消除了包裹相位图中一个条纹周期内相邻像素点间大于π的相位突变。 相似文献
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甲硫氨酸-脑啡肽的分子动力学模拟 总被引:1,自引:1,他引:0
The conformational properties of Met-enkephalin (Tyr-Gly-Gly-Phe-Met) were investigated by high temperature quenched molecular dynamics simulations in vapor. Each of these selected structures were then analyzed according to their backbone(φ,Ψ) conformational distributions and sorted into 13 families by computing the rms difference between the Cα-C backbone fragments of each residue over all the structures. Selected lowest energy conformations from each of 13 families were thoroughly energy minimized. The results of simulations show that Met-enkephalin is a flexible molecule. It shows a type Ⅰβ-turn, with the Gly2 carbonyl forming a hydrogen bond with the Met5 amino proton and a type Ⅱβ turn, with the Tyr1 amino proton forming a hydrogen bond with the Phe4 carbonyl. The multiple fit were carried out for all of the 13 conformers with morphine(9 atoms on the pharmacophore groups). F2 and F6 were the most similar to morphine. The rms were 0.0504 nm and 0.0726 nm. The results of simulations also show that Tyr amino N corresponds to N on piperidine ring in morphine, Tyr phenol corresponds to the phenol in morphine, the aromatic ring of Phe corresponds to the cyclohexene ring in morphine. The distances between the three pharmacophores, d1 (Tyr N to Tyr OH), d2 (Tyr N to Tyr du1), d3(Tyr N to Phe du2) and d4(Tyr N to Phe du2) were found to be about 0.8, 0.5, 0.7-0.9 and 0.5 nm, respectively, the corresponding, distances of morphine were found to be 0.7697(N18 to O6),0.5143(N18 to du25), 0.3962(N18 to du24)和0.5566(N18 to O15)nm. Therefore, they may be acted on the same receptor. This model should aid in pharmaceutical design of peptide and nonpeptide ligands with opioid. 相似文献