金纳米棒的飞秒激光组装研究

金属纳米粒子对于研究表面等离子体共振具有非常重要的意义,其自组装形成的功能组装体能够展现出更加优异的整体协同性能.本文通过飞秒激光加工对金纳米棒直接进行组装,不引入其它的修饰剂,过程简单、快速(约1 min),不仅保留了金纳米棒表面等离子特性,且可以实现金纳米棒的任意精细图案化.将组装的微纳结构用于微流控芯片表面增强拉曼散射探测,可以得到很好的增强效果,为等离子体器件的制备提供了新的方法.     

基于局部Gabor二进制模式的高光谱伪装目标图像分类(英文)

为提高光谱伪装目标图像分类精度,提出了一种基于局部Gabor二进制模式(LGBP)的空间分类方法。LGBP作为一种多尺度算法,被用来提取高光谱图像的纹理特征。然后高光谱图像中的每一个像元可以用一个光谱特征向量及一个纹理特征向量表示。通过这种方法,增大类间距离。最后使用多核支持向量机结合光谱信息和空间纹理信息实现对高光谱伪装目标图像的分类。实验证明了该方法的有效性,分类总体精度和Kappa系数分别达到了95.6%和0.937。所提出的方法对于提高分类精度及鲁棒性具有重要意义。     

Local switching of chemical patterns through light-triggered unfolding of creased hydrogel surfaces

Visible light induces switching of surface chemical patterns based on hybrid gels of thermally responsive poly(N-isopropyl acrylamide) copolymer networks containing iron oxide nanoparticles. The swelling of these hybrid gels is reduced upon illumination (see picture), allowing controlled unfolding of creased features formed owing to an elastic surface instability.     

The impact of human activity patterns on asymptomatic infectious processes in complex networks

The study of the impact of human activity patterns on network dynamics has attracted a lot of attention in recent years. However, individuals’ knowledge of their own physical states has rarely been incorporated into modeling processes. In real life, for certain infectious processes, infected agents may not have any visible or physical signs and symptoms; therefore, they may believe that they are uninfected even when they have been infected asymptomatically. This infection awareness factor is covered neither in the classical epidemic models such as SIS nor in network propagation studies. In this article, we propose a novel infectious process model that differentiates between the infection awareness states and the physical states of individuals and extend the SIS model to deal with both asymptomatic infection characteristics and human activity patterns. With regards to the latter, we focus particularly on individuals’ testing action, which is to determine whether an individual is infected by an epidemic. The simulation results show that less effort is required in controlling the disease when the transmission probability is either very small or large enough and that Poisson activity patterns are more effective than heavy-tailed patterns in controlling and eliminating asymptomatic infectious diseases due to the long-tail characteristic.     

Inverse estimation of indoor airflow patterns using singular value decomposition

The fast pace in the development of indoor sensors and communication technologies is allowing a great amount of sensor data to be utilized in various areas of indoor air applications, such as estimating indoor airflow patterns. The development of such an inverse model and the design of a sensor system to collect appropriate data are discussed in this study. Algebraic approaches, including singular value decomposition (SVD), are evaluated as methods to inversely estimate airflow patterns given limited sensor measurements. In lieu of actual sensor data, computational fluid dynamics data are used to evaluate the accuracy of the airflow patterns estimated by the inverse models developed in this study. It was found that the airflow patterns estimated by the linear inverse SVD model were as accurate as those estimated by the nonlinear inverse-multizone model. For the zones tested, sensor measurements along on the walls and near the inlet and outlet provided the greatest improvement in the accuracy of the estimated airflow patterns when compared with the results using measurements from other locations.     

Computer‐aided prediction of toxicity with substructure pattern and random forest

Toxicity of chemicals induced by different factors is an important consideration, especially during the drug research and development process. Thus, there is urgent need to develop computationally effective models that can predict the toxicity or adverse effects of chemicals for a specific class of chemicals. In this study, random forest (RF) was used to classify five toxicity data sets from Distributed Structure‐Searchable Toxicity database network, using substructure fingerprints calculated directly from simple molecular structure. Three model validation approaches, out‐of‐bag validation incorporated in RF, fivefold cross‐validation, and an independent validation set, were used for assessing the prediction capability of our models. The chemical space analysis of data sets was explored by multidimensional scaling plots, and outlying molecules were also detected by the proximity measure in RF. At the same time, the important substructure fingerprints, recognized by the RF technique, gave some insights into the structure features related to toxicity of chemicals. The results obtained showed that these in silico classification models with substructure patterns and RF are applicable for potential toxicity prediction of chemical compounds. Copyright © 2012 John Wiley & Sons, Ltd.     

锯齿型石墨烯带缺陷改性方法研究

采用基于密度泛函理论的非平衡格林函数, 对具有不同缺陷构型的锯齿型石墨烯带(zigzag graphene nanoribbon, ZGNR) 的输运性质进行了理论计算与模拟. 研究表明, 相同数目、 不同构型缺陷结构对ZGNR的导电特性将产生不同的影响. 如A-B构型双空缺对ZGNR电导的影响最为显著, 而A-A构型双空缺对其电导的影响最小. 更为重要的是, 当引入碳环构型缺陷时, ZGNR将被改性, 即由原本的金属性质转变为半导体性质, 为缺陷调控石墨烯导电特性提供了理论依据.     

Towards a geometrical classification of statistical conservation laws in turbulent advection

The paper revisits the compressible Kraichnan model of turbulent advection in order to derive explicit quantitative relations between scaling exponents and Lagrangian particle configuration geometry.     

三维显示中基于彩色叠栅条纹的视差障栅参数设计

为确定三维显示中视差障栅(PB)的最优参数,提出一种基于彩色叠栅条纹的PB参数设计方法。液晶显示器(LCD)和PB简化为相应参数的黑白光栅模型,而具有特定参数的特定辐射光栅作为周期和倾角变化的PB模型,通过序数方程和傅里叶分析方法分析特定辐射光栅和LCD单色等效黑白光栅的叠加图样,由此推断出不同PB周期的低频主导条纹频率组项,然后利用傅里叶理论的部分和提取方法(PSE)分析不同PB周期的低频主导叠栅条纹的强度轮廓,得出PB的最佳节距和相应倾斜角度。实验结果表明,所设计的PB三维显示系统没有出现降低像质的叠栅条纹,具有较好的三维显示效果。     

Numerical approximation of Turing patterns in electrodeposition by ADI methods

In this paper we study the numerical approximation of Turing patterns corresponding to steady state solutions of a PDE system of reaction–diffusion equations modeling an electrodeposition process. We apply the Method of Lines (MOL) and describe the semi-discretization by high order finite differences in space given by the Extended Central Difference Formulas (ECDFs) that approximate Neumann boundary conditions (BCs) with the same accuracy. We introduce a test equation to describe the interplay between the diffusion and the reaction time scales. We present a stability analysis of a selection of time-integrators (IMEX 2-SBDF method, Crank–Nicolson (CN), Alternating Direction Implicit (ADI) method) for the test equation as well as for the Schnakenberg model, prototype of nonlinear reaction–diffusion systems with Turing patterns. Eventually, we apply the ADI-ECDF schemes to solve the electrodeposition model until the stationary patterns (spots & worms and only spots) are reached. We validate the model by comparison with experiments on Cu film growth by electrodeposition.