Fractal analysis of polyethylene catalysts surface morphologies based on wavelet transform modulus maxima method

Surface morphologies of supported polyethylene (PE) catalysts are investigated by an approach combining fractal with wavelet. The multiscale edge (detail) pictures of catalyst surface are extracted by wavelet transform modulus maxima (WTMM) method. And, the distribution of edge points on the edge image at every scale is studied with fractal and multifractal method. Furthermore, the singularity intensity distribution of edge points in the PE catalyst is analyzed by multifractal spectrum based on WTMM. The results reveal that the fractal dimension values and multifractal spectrums of edge images at small scales have a good relation with the activity and surface morphology of PE catalyst. Meanwhile the catalyst exhibiting the higher activity shows the wider singular strength span of multifractal spectrum based on WTMM, as well as the more edge points with the higher singular intensity. The research on catalyst surface morphology with hybrid fractal and wavelet method exerts the superiorities of wavelet and fractal theories and offers a thought for studying solid surfaces morphologies. Supported by the Chinese Petroleum & Chemical Corporation Development Department (Grant No. x504024)     

柠檬酸在D354树脂上的动态交换过程

在３５℃下，实验测定了柠檬酸溶液在Ｄ３５４树脂固定床离子交换柱中的穿透曲线，研究了进口浓度、进口流速及柱高对穿透曲线的影响。用简单线性推动力模型描述固定床动态过程，考察了轴向返混对穿透曲线的影响，并从穿透曲线回归得到总传质系数，模型计算值与实验数据符合良好。同时还研究了用强酸顶替法洗脱柠檬酸。     

TiO2 nanotube/ZnO nanorod/CdS on Ti mesh with three-dimensional array structure for photocatalytic degradation under visible light irradiation

Research on Chemical Intermediates - The three-dimensional (3D) TiO2 nanotube arrays (TNTA) were prepared by electrochemical anodization of Ti mesh in a mixed electrolyte solution of (NH4)2SO4 and...     

激光诱导单层纳米硅结构的形成及其发光特性

结合激光退火与常规热退火方法对超薄非晶硅层作用,在绝缘衬底上获得了高密度的、均匀的单层纳米硅结构.所得样品通过原子力显微镜、透射电子显微镜和Raman散射谱进行表征,证实了晶化过程的发生和纳米硅晶粒的形成.在得到的5nm厚晶化样品中观察到在660nm左右范围内光致发光峰,初步的分析表明其发光与纳米硅晶粒的形成有关.     

Hybrid Genetic Algorithm for the Design of Modified Frequency-Response Masking Filters in a Discrete Space

This paper presents the design of high-speed, arbitrary bandwidth sharp finite impulse response filters with signed powers-of-two coefficients based on a modified frequency-response masking (FRM) structure. A novel hybrid genetic algorithm (HGA) is proposed to jointly optimize all subfilters in a discrete space. The proposed HGA introduces the simulated annealing technique into the genetic algorithm (GA) optimization process and effectively prevents the GA from prematurely converging. It is shown, by means of examples, that FRM filters designed by the HGA achieve a significant reduction in the number of bits.     

Mechanism of Formation and Consequent Evolution of Active Cellulose during Cellulose Pyrolysis

An intermediate product that was yellow, soluble, and solid was obtained in a high-radiation flash pyrolysis reactor. Under two different radiant heat fluxes, the yields tended to both increase initially until achieving a steady state, and then increase again with the progress of reaction. The compositional analysis of the yellow product was performed on high performance liquid chromatography (HPLC). It was indicated that the product mainly consisted of oligosaccharides, glucose, levoglucosan, methylglyoxal and so on. The compounds including oligosaccharides such as cellobiose and cellotriose, and monosaccharides such as glucose were regarded as active cellulose. Under the higher heat flux, the relative yield of the active cellulose increased initially, followed by a decreasing trend, and achieved a maximum mass fraction of 68% (w) in the soluble yellow product. The oligosaccharides with higher degree of polymerization (DP) were the primary components. Under the lower heat flux the yield of active cellulose was relatively lower, achieving a maximum of about 57% (w), and more saccharides with lower DP were contained. It was suggested that active cellulose was quite unstable at high temperature, and easily decomposed into saccharides with lower DP, even char, volatiles, and gaseous products. Finally an improved mechanism was proposed to describe the reaction route of formation and consequent evolution of active cellulose during cellulose pyrolysis.     

Mechanism study of wood lignin pyrolysis by using TG–FTIR analysis

In order to study the pyrolysis mechanism of lignin, Van Soest's method was performed to extract lignin from different species of biomass. Fir and birch lignins were selected as the testing samples and corresponding microstructure was studied by a Fourier transform infrared spectrometry. Several characteristic bands were observed to show the presence and species of lignin. Following experimental research on pyrolysis of lignins from fir and birch were carried out on a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometry. Wood lignin undergoes in three consecutive stages, corresponding to the evaporation of water, the formation of primary volatiles and the subsequent release of small molecular gases. The main pyrolysis sections and the maximum weight loss rates are quite different for different wood species. Phenols are the main volatile products, in addition to alcohols, aldehydes, acids, and so on. As the main gaseous products, CO, CO₂, CH₄ are released out greatly.     

微分干涉差共焦显微膜层微结构缺陷探测系统

多层膜极紫外光刻掩模"白板"缺陷是制约下一代光刻技术发展的瓶颈之一,为提高对掩模"白板"上的膜层微结构缺陷的分辨能力,提出了一种微分干涉差共焦显微探测系统方案。基于标量衍射理论,计算了系统横向和轴向分辨率。利用MATLAB建模仿真,在数值孔径为0.65、工作波长为405 nm时,分析比较了微分干涉差共焦显微系统、传统显微系统和共焦显微系统的分辨率。结果表明微分干涉差共焦显微系统具有230 nm的横向分辨率和25 nm轴向台阶高度差的分辨能力(对应划痕等缺陷形式)。此外,仿真和分析了实际应用中探测器尺寸、样品轴向偏移等的影响,模拟分析了膜层微结构缺陷的探测,结果表明本系统可以探测200 nm宽、10 nm高的微结构缺陷,较另外两种系统有更好的探测能力。     

Noncontact temperature measurement by means of CCD cameras in a participating medium

An original technique was presented for noncontact three-dimensional temperature field measurement in a participating medium using radiative information captured by a CCD camera. This technique was based on the backward Monte Carlo method and was faster and more efficient than traditional techniques based on the forward Monte Carlo method. A numerical simulation case was adopted to validate the technique. It was found that the technique was capable of reconstructing the three-dimensional temperature field well, even with noisy input data.     

非对称碳氢扩散火焰内烟黑浓度与温度联合重建模型研究

基于烟黑热辐射传递过程,提出了非对称碳氢扩散火焰断面内烟黑浓度和温度分布的联合层析重建模型.应用最小二乘QR矩阵分解算法模拟分析了传感器数量和布置方式对重建结果的影响以及模型的抗噪能力.计算结果表明,当4个320像素线阵电荷耦合辐射投影传感器(CCD)成非正对布置时,浓度场重建结果最大误差小于2.5%,温度场重建结果最大误差小于0.2%.此外CCD正对布置将导致重建误差向中心聚集.从对含噪声数据的重建结果看,应用联合层析重建模型,辐射能传感器的信噪比不应低于60dB. 关键词： 非对称火焰 层析重建 最小二乘QR矩阵分解算法 联合重建