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131.
Yuan X Yan N Katsyuba SA Zvereva EE Kou Y Dyson PJ 《Physical chemistry chemical physics : PCCP》2012,14(17):6026-6033
Pd nanoparticles (NPs) with a small size and narrow size distribution were prepared from the decomposition of Pd(OAc)(2) in a series of hydroxyl-functionalized ionic liquids (ILs) comprising the 1-(2'-hydroxylethyl)-3-methylimidazolium cation and various anions, viz. [C(2)OHmim][OTf] (2.4 ± 0.5 nm), [C(2)OHmim][TFA] (2.3 ± 0.4 nm), [C(2)OHmim][BF(4)] (3.3 ± 0.6 nm), [C(2)OHmim][PF(6)] (3.1 ± 0.7 nm) and [C(2)OHmim][Tf(2)N] (4.0 ± 0.6 nm). Compared with Pd NPs isolated from the non-functionalized IL, [C(4)mim][Tf(2)N] (6.2 ± 1.1 nm), it would appear that the hydroxyl group accelerates the formation of the NPs, and also helps to protect the NPs from oxidation once formed. Based on the amount of Pd(OAc)(2) that remains after NP synthesis (under the given conditions) the ease of formation of the Pd NPs in the [C(2)OHmim](+)-based ILs follows the trend [Tf(2)N](-), [PF(6)](-) > [BF(4)](-) > [OTf](-) > [TFA](-). Also, the ability of the [C(2)OHmim](+)-based ILs to prevent the Pd NPs from undergoing oxidation follows the trend [Tf(2)N](-) > [PF(6)](-) > [TFA](-) > [OTf](-) > [BF(4)](-). DFT calculations were employed to rationalize the interactions between Pd NPs and the [C(2)OHmim](+) cation and the various anions. 相似文献
132.
The developments in World Wide Web and the advances in digital data collection and storage technologies during the last two decades allow companies and organizations to store and share huge amounts of electronic documents. It is hard and inefficient to manually organize, analyze and present these documents. Search engine helps users to find relevant information by present a list of web pages in response to queries. How to assist users to find the most relevant web pages from vast text collections efficiently is a big challenge. The purpose of this study is to propose a hierarchical clustering method that combines multiple factors to identify clusters of web pages that can satisfy users?? information needs. The clusters are primarily envisioned to be used for search and navigation and potentially for some form of visualization as well. An experiment on Clickstream data from a processional search engine was conducted to examine the results shown that the clustering method is effective and efficient, in terms of both objective and subjective measures. 相似文献
133.
Xiuhua Wang Jisheng Kou Chuanqing Gu 《Journal of Optimization Theory and Applications》2012,153(3):779-793
In this paper, we consider the semilocal convergence of a class of modified super-Halley methods for solving nonlinear equations
in Banach spaces. The semilocal convergence of this class of methods is established by using recurrence relations. We construct
a system of recurrence relations for the methods, and based on it, we prove an existence–uniqueness theorem that shows the
R-order of the methods. 相似文献
134.
By using molecular dynamics simulation, we have investigated systematically the feasibility of continuous unidirectional water flux across a deformed single-walled carbon nanotube (SWNT) driven by an oscillating charge outside without osmotic pressure or hydrostatic drop. Simulation results indicate that the flux is dependent sensitively on the oscillating frequency of the charge, the distance of the charge from the SWNT, and the asymmetry of the water-SWNT system. A resonance-like phenomenon is found that the water flux is enhanced significantly when the period of the oscillation is close to twice the average hopping time of water molecules inside the SWNT. These findings are helpful in developing a novel design of efficient functional nanofluidic devices. 相似文献
135.
Xiaojun Wang Isaac Elishakoff Zhiping Qiu Changhe Kou 《International Journal of Solids and Structures》2009,46(13):2539-2546
Hybrid theoretical, experimental and numerical method is proposed for free vibration and buckling of composite shell with unavoidable scatter in elastic moduli. Based on the Goggin’s measurement techniques, the elastic moduli for material T300-QY8911 are measured, and a set of experimental points are obtained. The measurements of elastic moduli are quantified by either (1) the smallest ellipsoid and (2) the smallest four-dimensional uncertainty hyper-rectangle. Then uncertainty propagation in vibration and buckling problems of composite shell by ellipsoidal analysis and interval analysis are, respectively, studied from the theoretical standpoint. Comparison between these analyses is performed numerically. 相似文献
136.
Using Parisi and Sourlas dimensional reduction, four-dimensional quantum chromodynamics is reduced to a two-dimensional principal chiral model by suitable superspace embedding. The frame Ta cannot be regarded as a fixed one and the frame connection field \varωμ(x) becomes a dynamical gauge field in two dimensions, giving rise to a confining potential. As a result of the original SU(3) Yang-Mills field obtains another SU(3) local symmetry and turns into SU(3)×SU(3) local symmetry-one group element as exp (iδ\varphiaTa) with fixed frame Ta, the other gauging the frame Ta. 相似文献
137.
以苯乙烯、甲基丙烯酸甲酯、丙烯腈等单体或它们的混合物为硬单体,天然胶乳为弹性组分,经多步种子乳液聚合法制得了在天然胶乳的粒子上镶嵌硬聚合物相的互穿网络型乳胶粒子.考察了十二烷基硫酸钠、十二烷基苯磺酸钠、壬基酚聚氧乙烯醚、油酸等乳化体系,过硫酸钾、过氧化苯甲酰热引发体系及异丙苯过氧化氢-四乙烯五胺、叔丁基过氧化氢-四乙烯五胺等氧化还原引发体系对聚合反应的影响.研究了交联剂用量对互穿结合率、溶胶含量的影响及溶胀时间、硬单体组成、乳化剂种类对乳胶粒子形态的影响,确定了适宜的聚合配方和工艺条件.透射电镜观察乳粒形态结果表明,单一使用极性或非极性单体,仅得到核-壳结构乳液,而采用不同极性单体复合、溶胀、互穿,得到的是镶嵌硬聚合物型乳粒结构. 相似文献
138.
139.
在生物化学领域中弄清金属酶活性中心的结构和氧化态是至关重要的。“键价和分析”是根据金属 配体键长数据确定固体中金属离子氧化态的一种方便可行的方法 ,它已用于金属蛋白、金属酶以及高温超导体中金属氧化态的指派。本文拟介绍该方法的要点及其实际应用。 相似文献
140.
酸性介质中Os(Ⅳ)对溴酸钾氧化DBC-偶氮肿的褪色反应有明显的催化作用,据此反应建立了微量娥的催化光度分析法,锇在1.0-20.0μg·L-1符合比耳定律.反应在水相中进行,灵敏度高,简便快速,用于贵金属精矿中娥的测定,结果满意. 相似文献