金膜上亚波长小孔阵列表面等离激元颜色滤波器偏振性质

金属薄膜上制备的表面等离激元颜色滤波器具有很强的颜色可调性. 在200 nm厚的金膜上, 通过聚焦离子束刻蚀, 制备一系列周期逐渐变化的圆形、方形、矩形亚波长尺寸小孔方阵列表面等离激元颜色滤波器, 改变入射光的偏振方向, 观察其超透射滤波现象. 研究发现: 对于矩形小孔阵列, 其透射光颜色随入射光偏振方向的变化而改变; 而对于圆形、方形的小孔阵列, 其透射光颜色对入射光的偏振方向并不敏感. 分析表明, 对于金膜上刻蚀的小孔结构, 虽然结构的周期性导致的表面等离激元极化子会对透射光的颜色变化产生一定影响, 但是随小孔形状变化的局域表面等离激元共振才是影响透射光颜色的决定性因素. 如果入射光没有在小孔中激发出局域表面等离激元, 则表面等离激元极化子对透射光的影响也会消失. 根据不同形状小孔周期结构透射光颜色随入射光的偏振变化特点, 制备出了包含两种小孔形状的复合周期结构. 随着入射光偏振方向的改变, 该结构会显示出不同的颜色图案. 关键词： 表面等离激元极化子 局域表面等离激元 颜色滤波器 亚波长小孔阵列     

基于任务量的网格资源管理模型研究

计算网格额外开销随任务量增大而急剧下降,小型任务的开销是相对很高的.鉴于这个特性对不同任务量的任务进行不同并行度划分,并建立相应资源管理模型,将资源管理分为作业量分析器,本地资源管理器,全局资源管理器,对提交的作业进行规模评估,根据任务量进行并行处理,任务量小的尽量减小并行性,大任务量的可以增大并行度.这样的处理方法避免了小型任务中中间件和网络传输的大量消耗,又增加了大规模任务的并行度,减少了执行时间.总体上减少了系统开销,提高了网格利用率,更加有利于网格的发展.     

IS THERE UNIT ROOT IN THE NITROGEN OXIDES EMISSIONS: A MONTE CARLO INVESTIGATION?

Abstract Use of the time‐series econometric techniques to investigate issues about environmental regulation requires knowing whether air pollution emissions are trend stationary or difference stationary. It has been shown that results regarding trend stationarity of the pollution data are sensitive to the methods used. I conduct a Monte Carlo experiment to study the size and power of two unit root tests that allow for a structural change in the trend at a known time using the data‐generating process calibrated to the actual pollution series. I find that finite sample properties of the Perron test are better than the Park and Sung Phillips‐Perron (PP) type test. Severe size distortions in the Park and Sung PP type test can explain the rejection of a unit root in air pollution emissions reported in some environmental regulation analyses.     

Formulation of commons dilemma: Dawes model reconsidered

This paper examines Dawes (1975) model on commons dilemma (CD) situation and proposes an alternative model which formulates CD. Firstly, it makes clear that Dawes model does not have the characteristics of CD. Secondly, it specifies “resource unit condition” which models of commons dilemma must satisfy. Thirdly, it presents CD model, which is obtained by setting the condition in Dawes model. And lastly, it examines some nature of the proposed model and find that in CD situation, fine is distributed proportionally to each player's property.     

Multistrain edge‐based compartmental model on networks

Multistrain diseases, which are infected through individual contacts, pose severe public health threat nowadays. In this paper, we build competitive and mutative two‐strain edge‐based compartmental models using probability generation function (PGF) and pair approximation (PA). Both of them are ordinary differential equations. Their basic reproduction numbers and final size formulas are explicitly derived. We show that the formula gives a unique positive final epidemic size when the reproduction number is larger than unity. We further consider competitive and mutative multistrain diseases spreading models and compute their basic reproduction numbers. We perform numerical simulations that show some dynamical properties of the competitive and mutative two‐strain models.     

A relaxation Riemann solver for compressible two-phase flow with phase transition and surface tension

The dynamics of two-phase flows depend crucially on interfacial effects like surface tension and phase transition. A numerical method for compressible inviscid flows is proposed that accounts in particular for these two effects. The approach relies on the solution of Riemann-like problems across the interface that separates the liquid and the vapour phase. Since the analytical solutions of the Riemann problems are only known in particular cases an approximative Riemann solver for arbitrary settings is constructed. The approximative solutions rely on the relaxation technique.The local well-posedness of the approximative solver is proven. Finally we present numerical experiments for radially symmetric configurations that underline the reliability and efficiency of the numerical scheme.     

Detecting pore size distribution of activated carbon by low-field nuclear magnetic resonance

In this study, the transverse relaxation time (T₂) of activated carbon (AC) in different relative environment humidity was detected firstly by low-field nuclear magnetic resonance (LFNMR). The pore size (diameter) of AC distributions was calculated by the relationship between T₂ and surface relaxation rate (ρ), where ρ was obtained by the detection of nine porous materials with known pore size. The results showed that the pore size distributions of AC calculated by ρ < 0.19 nm/ms were in good agreement with that obtained by nitrogen adsorption method and proved that LFNMR as a new detection method was feasible for characterizing AC pore size distribution.     

Crown evolution kinematics of a camellia oil droplet impacting on a liquid layer

The phenomenon of droplet impact on an immiscible liquid is encountered in a variety of scenarios in nature and industrial production. Despite exhaustive research, it is not fully clear how the immiscibility of the liquid on which a droplet impacts affects the crown evolution. The present work experimentally investigates the evolution kinematics of a crown formed by the normal impact of a camellia oil droplet on an immiscible water layer. Based on discussion of dynamic impact behaviors for three critical Weber numbers (We), the radius of the crown and its average spreading velocity are compared with those of previous theoretical models to discuss their applicability to the immiscible liquid. The evolution kinematics (morphology and velocity) are analyzed by considering the effects of the We and layer thickness. Furthermore, the ability of crown expansion in radial and vertical directions is characterized by a velocity ratio. The results show that our experimental crown radius still follows a square-root function of evolution time, which agrees with the theoretical predictions. The dimensionless average spreading velocity decreases with We and follows a multivariate power law, while the dimensionless average rising velocity remains constant. The velocity ratio is shown to linearly increase with We, demonstrating that the rising movement in crown evolution gradually enhances with We. These results are helpful for further investigation on the droplet impact on an immiscible liquid layer.     

排烟增湿脱硫活化反应器内液滴──脱硫剂颗粒碰撞的数值模拟

排烟增湿脱硫活化反应器内液滴──脱硫剂颗粒碰撞的数值模拟唐庆，徐旭常（清华大学热能工程系北京１０００８４）关键词液滴－颗粒碰撞，脱硫，数值模拟要有效的控制ＳＯＺ的污染，降低燃煤电厂排烟中ＳＯＺ的浓度显得尤为重要。在众多的烟气脱硫技术中，排烟增湿活化脱...     

KIT-6负载CeO2催化CO2和甲醇合成碳酸二甲酯

采用不同老化温度(80、100、120和150℃)合成了一系列KIT-6载体,并通过浸渍法制备了相应的CeO_2/KIT-6催化剂。结合X射线衍射、N_2物理吸附、NH_3程序升温脱附、CO_2程序升温脱附、透射电子显微镜、傅里叶变换红外光谱和X射线光电子能谱等表征结果,详细考察了老化温度对KIT-6结构以及CeO_2/KIT-6催化剂直接催化CO_2和甲醇合成碳酸二甲酯(DMC)反应活性的影响。结果表明,不同老化温度下制备的KIT-6均保持其独特的三维孔道结构。随着老化温度升高,KIT-6比表面积先增大后减小,当老化温度为100℃时,KIT-6比表面积达到最大(683 m~2·g~(-1))。KIT-6较高的比表面积有利于提高CeO_2分散度,进而提高暴露的活性位点数量,催化活性随催化剂表面中等碱/酸性吸附位数量和Ce~(3+)含量的增加而逐渐提高。其中,CeO_2/100-KIT-6催化剂中CeO_2颗粒尺寸最小(5.9 nm),暴露的活性位数量最高,催化活性最佳。随后,考察了反应温度和压力对CeO_2/100-KIT-6催化活性的影响。随着反应温度提高,催化活性先升高后降低,当反应温度为140℃时,催化活性最高;且催化活性随反应压力的提高而逐渐增加。在反应温度为140℃、压力为6.8 MPa条件下,催化剂经6次循环后,DMC收率由15 mmol·g_(CeO_2)~(-1)逐渐降低至2.8 mmol·g_(CeO_2)~(-1),原因归结为反应过程中CeO_2纳米颗粒发生团聚,使暴露出的活性位数量减少。