Self‐organizing traffic lights at multiple‐street intersections

The elementary cellular automaton following rule 184 can mimic particles flowing in one direction at a constant speed. Therefore, this automaton can model highway traffic qualitatively. In a recent paper, we have incorporated intersections regulated by traffic lights to this model using exclusively elementary cellular automata. In such a paper, however, we only explored a rectangular grid. We now extend our model to more complex scenarios using an hexagonal grid. This extension shows first that our model can readily incorporate multiple‐way intersections and hence simulate complex scenarios. In addition, the current extension allows us to study and evaluate the behavior of two different kinds of traffic‐light controller for a grid of six‐way streets allowing for either two‐ or three‐street intersections: a traffic light that tries to adapt to the amount of traffic (which results in self‐organizing traffic lights) and a system of synchronized traffic lights with coordinated rigid periods (sometimes called the “green‐wave” method). We observe a tradeoff between system capacity and topological complexity. The green‐wave method is unable to cope with the complexity of a higher‐capacity scenario, while the self‐organizing method is scalable, adapting to the complexity of a scenario and exploiting its maximum capacity. Additionally, in this article, we propose a benchmark, independent of methods and models, to measure the performance of a traffic‐light controller comparing it against a theoretical optimum. © 2011 Wiley Periodicals, Inc. Complexity, 2012     

GaAs异质结材料BOA光开关特性分析

本文较为详细地讨论了GaAs异质结材料BOA型光开关的特性;并应用转移矩阵理论和有效折射率法计算和分析了电极结构与器件半波电压和串音度的关系.结果表明:通过优化设计电极的宽度可以获得BOA型光开关最小的半波电压;电极位置的对称性对器件串音度起决定性的影响.采用自对准工艺技术可以比较准确的控制电极的位置.分析表明:要得到<-40dB的串音度,电极位置偏差必须小于0.3μm.     

Peptide anchored Langmuir–Blodgett films of a fullerene amphiphile

A new amphiphilic derivative of fullerene C₆₀ bearing an oligoglycyl tail (C₆₀CHCOgly₂OEt, 2) formed stable Langmuir floating films at the air–water interface. This occurred when the molecular assembly was stabilized by anchoring the amphiphilic C₆₀'s to the aqueous subphase, via hydrogen bonding interactions between a dipeptide (Gly–L–Leu) dissolved in the water subphase, and the oligoglycyl chain. The compression (π−A) isotherm of the Langmuir floating film constructed in such a way showed no hysteresis, was steep, and evidenced that the monolayer collapsed at a surface pressure π65 mN m⁻¹, thus confirming that the film was tightly packed, extremely stable, and rigid. A limiting area per molecule of 89.1 Ų was extrapolated, in agreement with the calculated cross-section area of the C₆₀ fullerene. On the contrary, when the dipeptide was absent and pure water was used as the subphase, the π−A isotherm yielded a limiting area <55 Ų which indicated the formation of multiple layers; moreover it showed significant hysteresis, the film was fragile, and it collapsed at π≈50 mN m⁻¹. Once anchored by the dipeptide, the floating monolayer of 2 could be transferred onto hydrophobic quartz, glass and silicon substrates, by successive vertical dipping cycles, each cycle made up of two down-strokes and two up-strokes, to yield the Langmuir–Blodgett film. Up to 200 down- and up-strokes could be repeated reproducibly, a noteworthy result for non-covalently assembled LB films of fullerenes. The transfer ratio was 1.0, except for the second down-stroke of each cycle that gave a transfer ratio of zero, making the sequence of successful transfers: D, U, U, (cleaning and spreading), D, U, U, (cleaning and spreading), and so on (D=down-stroke, U=up-stroke). The total number of deposited layers was therefore 150. X-ray diffraction spectra were registered and exhibited a peak, which was fitted by a Montecarlo method of simulation to obtain the distribution of the repeat unit responsible for scattering; such distribution, with thickness between 20 and 60 Å, was consistent with the size of the amphiphile and the transfer sequence. The UV–Vis spectra of the LB film exhibited the characteristic C₆₀ bands, and the absorption peaks in the 200–400 nm range were proportional to the number of layers, indicating that the deposition was reproducible and that the molecular environment of C₆₀ in each layer remained constant.     

自成核对等规聚丙烯结晶行为和性能的影响

结晶聚合物的结晶动力学影响其形态结构 ,而形态结构的变化对材料的性能有着重要的影响 [1] .成核剂能有效地降低聚合物的球晶尺寸 ,提高材料的性能 [2 ] ,因此被广泛地应用于工业生产中 .自成核 (self- seeding nucleation)是指聚合物自身的微小晶粒作为晶核而诱导结晶生长的一种成核方式 [3 ,4 ] ,它具有很高的成核效率 ,并能有效地降低球晶尺寸 .本文研究了等规聚丙烯的自成核过程、结晶行为、形态结构及其对材料性能的影响 .1　实验部分1 .1　样品的制备　等规聚丙烯 (i PP)为广东茂名石油化学工业公司产品 ,牌号为 T3 6 F.将 i PP粒…     

自组装膜的几何厚度与电化学表观有效厚度

根据界面双层电容值可用来判定自组膜的存在 ,也能得到膜的几何厚度 ;但不能说明自组膜的完美程度 .由跨膜电子转移的速度常数 ,可以得到自组膜的电化学表观有效厚度 ,并定量描述非电活性的自组膜 (单分子层膜或双层膜 )中“倒塌”缺陷的程度 .二者数值不同但不矛盾 ,通过计算说明了自组膜中小面积的“倒塌”缺陷决定了跨膜电子转移的速度常数 ,但对自组膜电容的影响不大 .     

端羧基芳脂型超支化聚酯自组装性能的研究

利用聚电解质逐层浸渍 ( layer- by- layer dipping)法制备自组装膜是最近发展起来的进行表面改性的新方法[1～ 3] .一方面 ,从理论上来说 ,只要是带电荷的聚合物都可以利用该技术制备具有优异性能的自组装膜 ;另一方面 ,还可以通过调节溶液的 p H值和离子强度等控制阴阳离子的组装过程 ,从而控制自组装膜的内部结构和表面形态 ,为在纳米级范围内设计和控制聚合物聚集态内部结构提供了可能性 .近年来 ,具有高度支化结构的超支化分子由于具有独特的物理和化学性能而受到了广泛的关注 [4 ,5] ,但以聚电解质逐层浸渍法制备超支化分子自组装膜…     

含C60的聚电解质自组装膜微摩擦性能的研究

通过自由基引发溶液聚合反应,合成星状C₆₀-苯乙烯-丙烯酸聚合物,其钠盐作为高聚物负离子,与高聚物正离子的重氮树脂在云母上自组装成膜,利用紫外光照射反应,使膜层间连接的离子键转化成共价键.用原子力显微镜(AFM)和摩擦力显微镜(FFM)研究了不同链长和不同层数自组装膜的表面形貌及微摩擦性能.     

含磺化聚苯胺和重氮树脂自组装超薄膜的制备及其光电转换性能

具有共轭结构的高分子化合物正日益被人们所重视 ,并被应用于导电、光电、电致发光等方面的研究 [1～ 3] .聚合物较之传统的无机太阳能材料 (如硅半导体等 )具有价格低廉 ,可方便地改变结构等优点 ,其光电转换性能的研究主要集中在提高光电转化效率和可加工性能 [4 ,5]两个方面 .由于共轭高分子如聚苯胺在一般溶剂中的溶解性较差 ,人们通过合成取代聚苯胺来提高其溶解性 ,从而改善其加工性能 ,为最终提高其在功能器件中的应用提供保证 .磺化聚苯胺就是通过在苯环上引入磺酸基而使其成为一种水溶性的高聚物 .自组装技术自 1 991年由 Decher[…     

克尔介质中超连续谱的产生与自聚焦的抑制

 从（3+1）维非线性薛定谔方程出发,理论上分析了超短脉冲频谱展宽与自聚焦的影响因素。分析得出：通过改变泵浦光的功率和光束口径,可以实现光谱的极大展宽并避免自聚焦成丝。数值模拟了小口径强泵浦光束在BK7玻璃中的传输过程并进行了实验验证。模拟结果显示在超连续谱产生的同时小尺度调制被完全抑制。实验结果表明：降低泵浦光功率,使光束不会因为全光束自聚焦而发生塌陷,同时还能控制除自聚焦外的其它非线性效应,进而改善近场光束质量。由于自相位调制是超短超强脉冲产生超连续谱的重要机制之一,需要维持传输过程中的泵浦光功率,由此最佳的入射光功率应选在全光束自聚焦功率阈值附近。     

超支化聚合物制备方法的研究进展

超支化聚合物是一类可以通过一步法来合成的具有高度支化结构的体型大分子.经过二十年的研究,超支化聚合物由于其独特的结构和性能特点以及可实现规模化生产的特点, 已经迅速成为一类重要的和具有广阔应用潜力的高分子材料.本文从单体类型的角度介绍了超支化聚合物的主要制备方法及其发展历程,主要涉及ABx型,AB*型,A2 B3型以及潜在ABx型单体(包括开环聚合和偶合单体法)等,同时论述了各制备方法的优点和局限性 .