Constructions for optimal (u×v,{3,4},1,Q)-OOSPCs

Multiple-weight optical orthogonal signature pattern codes (OOSPCs) were introduced by Kwong and Yang for 2-D image transmission in multicore-fiber optical code-division multiple-access (OCDMA) networks with multiple quality of services (QoS) requirement. In this paper, an upper bound on the maximum code size of a $(u\times v,W,\lambda ,Q)$-OOSPC is obtained. A link between optimal $(u\times v,W,\lambda ,Q)$-OOSPCs and block designs is developed. Several infinite families of optimal $(u\times v,\{3,4\},1,Q)$-OOSPCs are presented by means of semi-cyclic group divisible designs ($(W,Q)$-SCGDDs) and perfect relative difference families.     

化学接枝改进ZnO-有机硅纳米复合材料的光学性能

采用N-(三甲氧基硅丙基)-4-叠氮-2,3,5,6-四氟苯甲酰胺(PFPA-silane)改性纳米氧化锌,并将PFPA-silane接枝在有机硅聚合物链上.接枝反应改变了纳米复合物的折光指数,并使ZnO纳米粒子与有机硅基体的折光指数更加匹配.这减少了纳米氧化锌粒子对光的散射作用,增加了纳米ZnO-有机硅纳米复合物的透明性.所制备的复合物通过接枝改性后透光率最多可提高50%.研究结果表明无机物和聚合物的折光指数的匹配程度可以通过偶联剂与聚合物基体的反应来进行调控.     

Single-walled carbon nanotubes as stationary phase in gas chromatographic separation and determination of argon, carbon dioxide and hydrogen

A chromatographic technique is introduced based on single-walled carbon nanotubes (SWCNTs) as stationary phase for separation of Ar, CO₂ and H₂ at parts per million (ppm) levels. The efficiency of SWCNTs was compared with solid materials such as molecular sieve, charcoal, multi-walled carbon nanotubes and carbon nanofibers. The morphology of SWCNTs was optimized for maximum adsorption of H₂, CO₂ and Ar and minimum adsorption of gases such as N₂, O₂, CO and H₂O vapour. To control temperature of the gas chromatography column, peltier cooler was used. Mixtures of Ar, CO₂ and H₂ were separated according to column temperature program. Relative standard deviation for nine replicate analyses of 0.2 mL H₂ containing 10 μL of each Ar or CO₂ was 2.5% for Ar, 2.8% for CO₂ and 3.6% for H₂. The interfering effects of CO, and O₂ were investigated. Working ranges were evaluated as 40-600 ppm for Ar, 30-850 ppm for CO₂ and 10-1200 ppm for H₂. Significant sensitivity, small relative standard deviation (RSD) and acceptable limit of detection (LOD) were obtained for each analyte, showing capability of SWCNTs for gas separation and determination processes. Finally, the method was used to evaluate the contents of CO₂ in air sample.     

受振颗粒“毛细”系统中的对流与有序化

将球形颗粒倒入内径较窄的管状容器时,管壁的曲率会对颗粒的堆积结构产生影响,存在壁效应. 实验表明通过连续的竖直方向的振动,壁效应可以被强化,颗粒可以经由对流由无序排列转变为稳定的同轴筒形“壳层”结构. 每一壳层内,颗粒是二维的六角密堆积, 在这一转变过程中,颗粒堆积率的径向分布由初始的衰减振荡转变为等幅振荡. 分析了堆积率的不均匀性及空气在对流中的作用,以及形成“壳层”结构的动力学过程,对“壳层”结构的稳定性亦进行了讨论. 关键词： 颗粒物质 对流 有序化 毛细     

Packing Countably Many Branchings with Prescribed Root‐Sets in Infinite Digraphs

We generalize an unpublished result of C. Thomassen. Let be a digraph and let be a multiset of subsets of V in such a way that any backward‐infinite path in D meets all the sets . We show that if all is simultaneously reachable from the sets by edge‐disjoint paths, then there exists a system of edge‐disjoint spanning branchings in D where the root‐set of is .     

New lower bounds for bin packing problems with conflicts

The bin packing problem with conflicts (BPC) consists of minimizing the number of bins used to pack a set of items, where some items cannot be packed together in the same bin due to compatibility restrictions. The concepts of dual-feasible functions (DFF) and data-dependent dual-feasible functions (DDFF) have been used in the literature to improve the resolution of several cutting and packing problems. In this paper, we propose a general framework for deriving new DDFF as well as a new concept of generalized data-dependent dual-feasible functions (GDDFF), a conflict generalization of DDFF. The GDDFF take into account the structure of the conflict graph using the techniques of graph triangulation and tree-decomposition. Then we show how these techniques can be used in order to improve the existing lower bounds.