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81.
Marcel Wild 《Semigroup Forum》2008,76(2):268-275
For any positive integers M and N we define a selfdually ordered band ℬ(M,N) of cardinality
and ask whether or not it is lattice-ordered. The origin of ℬ(M,N) in nonlinear signal processing is outlined. 相似文献
82.
This article reviews the synthesis and characterization of nanoparticles and nanowires grown in ordered mesoporous silicas (OMS). Summarizing work performed over the last 4 years, this article highlights the material properties of the final nanocomposite in the context of the synthesis methodology employed. While certain metal-OMS systems (e.g. gold in MCM-41) have been extensively studied this article highlights that there is a rich set of chemistries that have yet to be explored. The article concludes with some thoughts on future developments and challenges in this area. 相似文献
83.
采用溶剂挥发自组装结合提拉法,在石墨纤维表面制备有序介孔碳(Ordered mesoporous cabon,OMC)涂层,并开展其对水中氯苯类有机污染物的固相微萃取(SPME)测定.扫描电镜(SEM)结果显示,制备的OMC涂层完整,与基体结合紧密,厚度约为7μm.透射电镜(TEM)、X射线衍射(XRD)和氮吸附脱附结果证实,OMC涂层具有规整二维六方特征,比表面积和孔容分别为369.7 m2/g和0.28 cm3/g.以氯苯类污染物为分析对象,采用顶空固相微萃取与氢火焰气相色谱联用法对OMC涂层的萃取性能进行全面的评价,优化萃取时间和温度、解吸时间、搅拌速率、离子强度及顶空体积等萃取条件,并与商品化涂层进行比对.结果表明,最佳萃取条件为:萃取时间30 min,萃取温度50℃,脱附时间2 min,盐浓度0.35 g/mL,顶空体积15 mL.在最佳萃取条件下,检出限在0.05~0.15 μg/L之间;在1~1000 μg/L线性范围内,线性关系良好;7次平行样测定的相对标准偏差为4.1% ~6.4%.制备的OMC涂层的峰面积是商用聚二甲基硅氧烷/二乙烯基苯(Polydimethylsiloxane/divinylbenzene,PDMS/DVB)涂层的2倍,商用聚丙烯酸酯(Polyacrylate,PA)涂层的18倍.将此涂层应用于两种实际水样中,4种氯苯均未检出,添加浓度为20 μg/L时,样品回收率分别为99.4%~114.5%和92.3%~ 97.0%. 相似文献
84.
In this work, we have developed a convenient and efficient method for the functionalization of ordered mesoporous carbon (OMC) using polyoxometalate H6P2Mo18O62·xH2O (P2Mo18). By the method, glassy carbon (GC) electrode modified with P2Mo18 which was immobilized on the channel surface of OMC was prepared and characterized for the first time. The large specific surface area and porous structure of the modified OMC particles result in high heteropolyacid loading, and the P2Mo18 entrapped in this order matrix is stable. Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption-desorption isotherm and X-ray diffraction (XRD) were employed to give insight into the intermolecular interaction between OMC and P2Mo18. The electrochemical behavior of the modified electrode was studied in detail, including pH-dependence, stability and so on. The cyclic voltammetry (CV) and amperometry studies demonstrated that P2Mo18/OMC/GC electrode has high stability, fast response and good electrocatalytic activity for the reduction of nitrite, bromate, idonate, and hydrogen peroxide. The mechanism of catalysis on P2Mo18/OMC/GC electrode was discussed. Moreover, the development of our approach for OMC functionalization suggests the potential applications in catalysis, molecular electronics and sensors. 相似文献
85.
在本文的第二部分中,我们研究了适合无限维实零点定理的序域的结构.通过嵌入,我们证明了,一个序域适合无限维实零点定理,当且仅当它的实闭包同构于域的某个具有无限维逼近性质的子域,这里是一个无裂缝的可除序群,{Γ}是指数在中,系数为实数的形式幂级数域. 相似文献
86.
An ordered adlayer of sulfate or bisulfate has been found on the unreconstructed Au(100) surface in 0.1 M H2SO4 by in-situ STM. The ordered adlayer is formed concomitantly with lifting of the (hex)-reconstruction. The new structure consists of sulfate/bisulfate rows that run parallel to the edges of the islands that were created during the (hex)→(1×1) transition. The distance between the adions within the rows is 4.0±0.3 Å, and that between rows 10.4±0.7 Å, corresponding to a
superstructure with a surface coverage of about 0.2. 相似文献
87.
Wang Hongfei 《化学物理学报(中文版)》2004,17(3):362-368
A simplified formulation for treating the linear and nonlinear spectroscopy of ordered molecular systems is presented,in order to help experimentalists to have an explicit physical picture and quantitative tool on using linear and nonlinear spectroscopy to study molecules in ordered molecular systems. This formulation is expended from our recent quantitative orientational and polarization treatment on second-order nonlinear spectroscopic techniques in interface studies,namely,the Second Harmonic Generation(SHG)and Sum Frequency Generation-Vibrational Polarization Spectroscopy(SFG-VPS). The key to this formulation is to simplify the effective linear or nonlinear molecular susceptibility and construct the general orientational functional with a clear approach to calculate the orientational and intensity parameters from the experimental parameters,which determines the orientational and polarization behavior of the general orientational functional in a particular experimental configuration. Also discussed are the advantages of coherent spectroscopic techniques over incoherent ones for the accurate measurement of orientation and ordering of ordered molecular system. 相似文献
88.
采用原位限域生长策略制备了一系列有序介孔碳负载的超小MoO3纳米颗粒复合物(OMC-US-MoO3). 其中, 有序介孔碳被用作基质来原位限域MoO3纳米晶的生长. 依此方法制备的MoO3纳米晶具有超小的晶粒尺寸(<5 nm), 并在介孔碳骨架内具有良好的分散度. 制得的OMC-US-MoO3复合物具有可调的比表面积(428~796 m2/g)、 孔容(0.27~0.62 cm3/g)、 MoO3质量分数(4%~27%)和孔径(4.6~5.7 nm). 当MoO3纳米晶的质量分数为7%时, 所得样品OMC-US-MoO3-7具有最大的孔径、 最小的孔壁厚度和最规整的介观结构. 该样品作为催化剂时, 表现出优异的环辛烯选择性氧化性能. 相似文献
89.
有序抖动半调图像的无损压缩算法 总被引:1,自引:0,他引:1
在分析不同有序抖动模板对所生成抖动半调图像的影响因素基础上,设计了尺度变化的分块及块间异或预处理策略,大大提高了二值游程长度.进而使用游程和哈夫曼相结合的编码思想提出了一种新的有序抖动半调图像无损压缩算法.仿真实验表明,该算法在编码效率上具有较大优势. 相似文献
90.
Isabel Izquierdo-Barba Edesia Sousa Juan Carlos Doadrio Antonio Luis Doadrio Joaquín Pérez Pariente Africa Martínez Florence Babonneau María Vallet-Regí 《Journal of Sol-Gel Science and Technology》2009,50(3):421-429
Ordered mesoporous materials exhibit potential features to be used as controlled drug delivery systems, including their wide
range of chemical compositions and their outstanding textural and structural properties. Therefore, it is possible to control
the drug release kinetics by tailoring such parameters. In this paper, mesoporous materials such as MCM-48 and SBA-15, which
present different pore sizes (3.7 and 8.8 nm) and structural characteristics (3D-bicontinuous cubic and 2D-hexagonal, respectively)
have been synthesized to evaluate their application as drug delivery system and to determine their influence on release kinetic
of ibuprofen. Moreover, a chemical modification of the SBA-15 mesoporous material with octadecyltrimethoxysilane has also
been performed to study its influence on the release rate of ibuprofen. The structural characteristics (3D cubic and 2D hexagonal
pore system) do not affect the release kinetic profiles of ibuprofen. On the contrary, the pore size affects highly to the
release kinetic profiles from first-order kinetic to zero-order kinetic for MCM-48 and SBA-15, respectively. Moreover, the
importance of surface functionalization was demonstrate through the very fast delivery of ibuprofen from SBA-15 mesoporous
materials functionalized with octadecyl chains. 相似文献