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51.
Ji ZF You JL Simon P Wang YY Hou M Wang LH Zhang GC Wan SM Fu PZ Wu YC Yin ST 《光谱学与光谱分析》2012,32(1):127-131
测量了BiB3O6晶体从常温到熔融态的拉曼光谱,考察了其温致结构变化和预测了熔体的结构基元。同时,采用量子化学从头计算和密度泛函理论对拉曼光谱进行了计算和结构分析。结果表明,随着温度的升高,对包含阳离子Bi的外部晶格和[BO3]3-硼氧三角形基团结构的温致结构影响有限,却有效地削弱了[BO4]5-硼氧四面体基团结构,其松弛度增加,稳定性变差,并在熔体结构中彻底消失。研究表明BiB3O6熔体主要以硼氧六元环[B6O12]6-的形式存在,阳离子Bi起电荷平衡作用,其氧配位数为3,有别于晶体中的6。 相似文献
52.
研究了空气下无配体Pd(OAc)2在弱碱碳酸钾存在下催化二苯胺和溴代芳烃的C—N偶联合成三苯胺类化合物.与传统合成方法相比,该反应可以在无配体存在下在空气和温和的条件下进行,即,无需无水无氧操作条件,操作特别方便.催化剂用量、碱、溶剂、反应温度、反应时间等因素对反应的影响均做了考察.优化的反应条件是:在Pd(OAc)2(3 mol%)和K2CO3(1.5 equiv.)存在下,二苯胺和溴代芳烃在DMSO中在空气下在90℃加热24 h.溴代芳烃上的吸电子基团和二苯胺上的给电子基团有利于该偶联反应的进行,其中4-硝基三苯胺的产率高达93%. 相似文献
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54.
一个图G的路分解是指一路集合使得G的每条边恰好出现在其中一条路上.记Pl长度为l-1的路,如果G能够分解成若干个Pl,则称G存在{Pl}—分解.关于图的给定长路分解问题主要结果有:(i)连通图G存在{P3}—分解当且仅当G有偶数条边(见[1]);(ii)连通图G存在{P3,P4}—分解当且仅当G不是C3和奇树,这里C3的长度为3的圈而奇树是所有顶点皆度数为奇数的树(见[3]).本文讨论了3正则图的{P4}—分解情况,并构造证明了边数为3k(k热∈Z且k≥2)的完全图Kn和完全二部图Kr,s存在{P4}—分解. 相似文献
55.
A new flexible hydrogen-bonded supramolecular host based on two deoxypyridinoline-bioinspired 6-hexanoic acid-substituted 3-hydroxypyridinium cations that adopt the twist and planar conformations and construct the orthogonal single helical scaffold and sheet structures with the triangular NO3− and spherical Br− guest anions, respectively. The results demonstrated not only the importance of rotational flexibility, anion shapes, and robust C—H⋯O hydrogen bonding, but also the good antibacterial activity with the potential antibacterial application. 相似文献
56.
Valeri T. Stefanov 《Stochastic Processes and their Applications》1985,19(2):305-314
This paper is devoted to efficient sequential estimation in stochastic processes whose corresponding sufficient statistics are processes with stationary independent increments. It is proved that a stopping time is efficient if and only if it represents a time of the first attaining of a hyperplane., which cannot ‘be passed’, in the sense which is made precise below. The problem of determining the explicit form of the hyperplanes which cannot ‘be passed’ is also discussed. 相似文献
57.
The aim of this study was to obtain quantitative characteristics of the ultraviolet absorption spectra as the molecular absorptivity at the wavelength of maximum absorbance. Organic as well as inorganic compounds were explored. A gas chromatography—ultraviolet absorption instrument has been used in the quantitative study of molecular ultraviolet absorption spectra in the vapour phase. The wavelength range studied was between 168 and 330?nm. The absorbance of 170 compounds was determined relative to perchloroethylene and their molecular absorptivities were calculated. For various groups of compounds, these relative absorptivities varied within two to three orders of magnitude. Standard curves were linear within four orders of magnitude from limit of quantification up to an absorption value of 1.5 absorbance units. The noise level was 3?×?10?5 absorbance units peak to peak at a bandwidth of 1.7?nm and a wavelength range from 180 to 330?nm was preferred. The detection limit for mesitylene was calculated to be 2 pg/s and for naphthalene 1 pg/s with 4?s store cycle time. 相似文献
58.
59.
超薄型平行平面镜的研制 总被引:1,自引:0,他引:1
超薄型平行平面镜的加工难度很高,往往在投入大量的辅助工装和较长的加工工时后,收效甚微。笔者用双平面分离器和平面环抛法相结合的工艺手段,经反复实践和试验,终于研制出厚度与直径的比例达1∶85、N=2、ΔN=0.2、θ=15″的平行平面镜。 相似文献
60.
K. Renee Fister 《Applicable analysis》2013,92(1-2):11-28
We consider boundary control and control via harvesting in a parabolic predator—prey system for a bounded region. The boundary control depicts the relationship between the boundary environment and the possibly harmful species. In addition, a proportion of the predator is harvested for profit. We choose to maximize the objective functional which incorporates the amount of the prey and the revenue of harvesting of the predator less the economic cost of sustaining a satisfactory boundary habitat and the cost due to the harvesting component. Moreover, we characterize the unique optimal control in terms of the solution to the optimality system, which is the state system coupled with the adjoint system. 相似文献