氢化丁苯共聚物结构的核磁共振波谱表征Ⅱ.微观结构的定量计算

在氢化丁苯共聚物¹³C-NMR谱脂肪碳部分谱带归属的基础上,根据各谱带的主要来源,推导出六个二单元浓度的计算公式。计算出二单元、一单元的相对含量,各结构单元的数均序列长度、嵌段含量和其它结构参数。加氢前后的¹H-和¹³C-NMR谱的组成计算结果基本一致。初步探讨了作为粘度指数改进剂的氢化丁苯共聚物微观结构与性能的关系,为合成提供了依据。     

The spectrum of BSA(v, 3, λ; α) with α = 2,3

In this article, a kind of auxiliary design BSA^* for constructing BSAs is introduced and studied. Two powerful recursive constructions on BSAs from 3‐IGDDs and BSA^*s are exploited. Finally, the necessary and sufficient conditions for the existence of a BSA(v, 3, λ; α) with α = 2, 3 are established. © 2006 Wiley Periodicals, Inc. J Combin Designs 15: 61–76, 2007     

Microperforated insertion units: An alternative strategy to design microperforated panels

Microperforated panels (MPPs) coupled to a rigid wall have been proposed recently as an alternative to porous absorbers in situations having concerns with bacterial contamination and small particles discharge, like food, pharmaceutical and microelectronic industries. There exists also an increasing interest for MPP absorbers in the transportation industry and civil engineering. In general, an optimally designed MPP with good broadband absorption requires many submillimetric holes distributed over a panel of also submillimetric thickness. Such thin plates or foils become so fragile that they need to be protected from mechanical damage. In this paper, an alternative strategy is investigated which allows the design of MPPs with panels of millimetric thickness while maintaining their acoustic performance. These absorbers, named microperforated insertion units (MIUs), avoid the structural problems of the classical MPPs. An assessment of the sound absorption properties of these structures is presented. Comparisons between calculations and measurements are also made under two experimental conditions: plane waves at normal incidence (impedance tube) and free field (anechoic room).     

The spectrum of cyclic BSA(ν, 3, λ; α) with α = 2, 3

Balanced sampling plans excluding contiguous units (or BSEC) were first introduced by Hedayat, Rao, and Stufken in 1988. In this paper, we generalize the concept of a cyclic BSEC to a cyclic balanced sampling plan to avoid the selection of adjacent units (or CBSA for short) and use Langford and extended Langford sequences to construct a cyclic BSA(ν, 3, λ; α) with α = 2, 3. We finally establish the necessary and sufficient conditions for the existence of a cyclic BSA(ν, 3, λ; α) where α = 2, 3. © 2005 Wiley Periodicals, Inc. J Combin Designs.     

Oxidative dehydrogenation of crotonaldehyde overK2HPMo12O40catalyst

Summary The oxidative dehydrogenation of crotonaldehyde to furan and maleic anhydride was carried out over K₂HPMo₁₂O₄₀catalyst. A positive effect of water vapor on furan formation is explained by ability of the catalyst to isomerize 2E- to 2Z-crotonaldehyde.</o:p>     

Group algebras of Kleinian type and groups of units

The algebras of Kleinian type are finite-dimensional semisimple rational algebras A such that the group of units of an order in A is commensurable with a direct product of Kleinian groups. We classify the Schur algebras of Kleinian type and the group algebras of Kleinian type. As an application, we characterize the group rings RG, with R an order in a number field and G a finite group, such that the group of units of RG is virtually a direct product of free-by-free groups.     

Markovian network processes: Congestion-dependent routing and processing

A Markovian network process describes the movement of discrete units among a set of nodes that process the units. There is considerable knowledge of such networks, often called queueing networks, in which the nodes operate independently and the routes of the units are independent. The focus of this study, in contrast, is on networks with dependent nodes and routings. Examples of dependencies are parallel processing across several nodes, blocking of transitions because of capacity constraints on nodes, alternate routing of units to avoid congestion, and accelerating or decelerating the processing rate at a node depending on downstream congestion. We introduce a general network process representing the numbers of units at the nodes and derive its equilibrium distribution. This distribution takes the form of a product of functions of vectors in which the arguments of the functions satisfy an interchangeability property. This new type of distribution may apply to other multi-variate processes as well. A basic idea in our approach is a linking of certain micro-level balance properties of the network routing to the processing rates at the nodes. The link is via routing-balance partitions of nodes that are inherent in any network. A byproduct of this approach is a general characterization of blocking of transitions without the restriction that the process is reversible, which had been a standard assumption. We also give necessary and sufficient conditions under which a unit moving in the network sees a time average for the unmoved units (called the MUSTA property). Finally, we discuss when certain flows between nodes in an open network are Poisson processes.This research was sponsored in part by Air Force Office of Scientific Research contract 84-0367.     

Carbon dendron nano-chains with π-extended conjugation based on end-capped N,N-dimethylamino in linear 1,4-phenylethynyl or in 1,5-naphthylethynyl subunits: fluorescence analysis

The synthesis of dendrons with the end-capped 5-(N,N-dimethylamino)naphthyl-1-ethynyl unit connected to conjugated naphthylethynyl or p-phenylethynyl chains, as the branches of the 1,3,5-substituted benzene core, have been undertaken by heterocoupling reaction between 1,3,5-triiodobenzene and the convenient end-capped 5-(N,N-dimethylamino)naphthylacetylene or 5-(N,N-dimethylamino)naphthylethynylphenylacetylene in the presence of the palladium-copper catalyst system, in excellent yields. The influence of the alternating naphthylethynyl-phenylethynyl chains on the fluorescence emission radiation, in the dendron structures, has been analyzed.     

Synthesis and binding studies of new bis-calix[4]arenes containing aromatic and heteroaromatic units

A series of new bis-calix[4]arenes containing different aromatic and heteroaromatic moieties have been synthesized. The complexing behavior of these bis-calix[4]arenes have been studied towards different metal ions and it has been found that these bis-calix[4]arenes bind silver ions selectively over other metal ions. The complexation has been studied by liquid-liquid extraction and by NMR and IR spectroscopy.     

Liquid-liquid extraction of copper (I) and copper (II) as ion-paired complexes with acyclic 2-thienyl-containing polythioether and triphenylmethane dye anion

Three acyclic polythioethers containing 2-thienyl units at both ends were synthesized and the effect of substituent on the extraction of copper(II) was studied. The methyl groups in the terminal thiophene ring have imparted an appreciable degree of increase in the percent extraction of copper(II), while the introduction of chlorine atoms into the 2-thienyl unit resulted in the reverse effect. Among the counter dye anions examined, tetrabromophenolphthalein ethylester was the best one for copper(II) extraction. The composition of extracted species was evaluated to be 122 (Cu(II)/polythioether/dye anion). Quantitative extraction of copper(I) was attained as complexes with various triphenylmethane dyes, i.e., bromocresol green, bromothymol blue, bromo-phenol blue and pyrogallol red. Copper(I) in organic phase was completely back-extracted with 2 mole/l sulfuric acid containing 10% hydrogen peroxide.