基于液晶取向变化检测有机胺化合物的方法

采用旋涂法在玻璃基底表面制备4-三乙氧基硅基丁腈有机膜.有机膜表面采用丝绒布进行摩擦和5％乙酸水溶液改性处理后成为特异敏感膜.将此敏感膜的载玻片面对面贴合后,在其间组装液晶E7分子膜,表征液晶分子排列状态;采用挥发法在敏感膜表面组装液晶膜,制备成了检测目标物的复合材料.采用此种材料对甲胺、乙胺和二乙胺等有机胺化合物及实验室常见干扰气体进行检测,发现只有有机胺化合物会对材料的液晶分子排列状态产生影响,导致液晶膜的亮度发生改变,从而实现对目标物的特异检测.对有机胺化合物检测过程中,其响应速率为V甲胺＜V乙胺＜V二乙胺,恢复速率为:V乙胺＜V乙胺＜V甲胺;刘乙胺的检出限为0.46 mg/m3.本方法具有较高的检测灵敏度,抗干扰能力较强且操作简单,可发展为现场检测有机胺化合物的新技术.     

Effects of deformation-induced orientation on cyclization and oxidation of polyacrylonitrile fibers during stabilization process

Orientation of copolymer polyacrylonitrile(PAN) chains during their deformation prior to stabilization and the further effect on the stabilization were investigated in detail.Results reveal that the orientation of PAN chains presents a saturation point of 69.51%when the deformation ratio reaches approximately 1.07,meanwhile the cyclization rather than the oxidation has a stronger dependence on the orientation of PAN chains during stabilization.The cyclization is facilitated that the cyclization degree is increasing while the activation energy is decreasing obviously as a consequence of the developing orientation of PAN fibers before the saturation point;however,it is restrained during the further deformation of PAN fibers after the point.The resulting carbon fibers obtained from the PAN fibers prepared at the saturation point possess the highest mechanical properties of 4.07 GPa in tensile strength and 249.0 GPa in tensile modulus.     

一种基于积分直方图的粒子滤波跟踪方法

用积分直方图技术提出了一种低复杂度的粒子滤波跟踪方法和基于积分颜色直方图的观测似然模型.采用积分方向直方图建立一个检测响应图,用其上的观测信息构建建议分布函数,在状态空间中似然概率较大的子空间中进行粒子采样.仿真结果表明,在采用大量粒子跟踪大目标时,提出的跟踪方法的计算复杂度明显低于直方图直接提取的粒子滤波方法, 而且在光照变化的条件下,比采用传统颜色Mean-Shift的跟踪方法准确.     

On the Ranks of Certain Semigroups of Orientation Preserving Transformations

We classify the unmixed squarefree lexsegment ideals and determine those which are Cohen–Macaulay.     

Unsteady motion of a spherical bubble in a complex fluid: Mathematical modelling and simulation

The nonlinear response of an oscillatory bubble in a complex fluid is studied. The bubble is immersed in a Newtonian liquid, which may have a dilute volume fraction of anisotropic additives such as fibers or few ppm of macromolecules. The constitutive equation for the fluid is based on a Maxwell model with an extensional viscosity for the viscous contribution. The model is considered new in the study of bubble dynamics in complex fluids. The numerical computation solves a system of three first order ordinary differential equations, including the one associated with the solution of the convolution integral, using a fifth order Runge–Kutta scheme with appropriated time steps. Asymptotic solutions of governing equation are developed for small values of the pressure forcing amplitude and for small values of the elastic parameter. A study of the bubble collapse radius is also presented. We compare the results predicted by our model with other model in the literature and a good agreement is observed. The calculated asymptotic solutions are also used to test the results of the numerical simulations. In addition, the orientation of the additives is considered. The angular probability density function is assumed to be a normal distribution. The results show that the model based on the fully aligned additives with the radial direction overestimates the tendency of the additives to stabilize the bubble motion, since the effect of extensional viscosity occurs due to the particle resistance to the movement throughout its longitudinal direction.     

ANALYSIS AND CHARACTERIZATION OF MICROSCOPIC MORPHOLOGY AND ORIENTATION STRUCTURE OF POLYANILINE POLYMERIZED IN A CONSTANT MAGNETIC FIELD

Conductive polyaniline(PAn-_M and PAn-_O) doped with dodecylbenzene sulfonic acid(DBSA) was synthesized by using emulsion polymerization method in the presence of a constant magnetic field(0.4 T) and the absence of magnetic field, respectively.The effects of magnetic field on the microscopic morphology and orientation structure of PAn were generally analyzed and characterized by using transmission electron microscope(TEM),X-ray diffraction(XRD) and through the conductivity anisotropy of unit resistance o...     

The influence of molecular orientation on the crosslinking/oxidative behaviour of iPP exposed to gamma radiation

This paper presents a study of the influence of structural peculiarities, uniaxial orientation and fibrillar structure on the radiation-induced changes in iPP. For the purposes of this study, iPP was oriented via solid-state stretching at elevated temperature to various draw ratios and, later on, gamma irradiated in air. In order to investigate orientation- and/or radiation-induced structural changes, optical microscopy (OM), scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), infrared spectroscopy (IR) and gel measurements were employed. To quantify the degree of molecular orientation, Herman’s orientation function (f_c), was used. IR spectroscopy and gel measurements were used to determine the changes in the oxidative degradation and degree of network formation, respectively. Sol-gel analysis was studied in detail using the Charlesby-Pinner (C-P) equation. The radiation-induced changes in the structure and evolution of oxygen-containing species were also studied through dielectric loss (tan δ) analysis in a wide frequency range; the polar groups that were introduced by irradiation in apolar iPP were considered as tracer groups. Conclusions derived according to different methods were compared. Presented results reveal two different radiation-induced dynamics; gamma irradiation of initial and fully developed fibrillar iPP structures leads to significantly different crosslinking and/or oxidation response.     

Orientation fluctuation trend of Pt and ZnO layers in film bulk acoustic resonator

ZnO-based film bulk acoustic resonator (FBAR) was fabricated with many ZnO/Pt layers by magnetron sputtering. All the layers are good crystallized and highly textured. By crystallographic test, the orientation fluctuation of Pt layer increases with increasing film thickness or stack layers, whereas that of ZnO layer decreases slightly. It is consistent with ZnO grain c-axis tilting observed using transmission electron microscopy. Due to these good quality layers, the device has a high resonate frequency of 3.94 GHz.     

Orientation Imaging Microscopy for the Transmission Electron Microscope

The resolution limit of Orientation Imaging Microscopy in the Scanning Electron Microscope is between 20 nA and 80 nA depending on the basic resolution/beam current performance of the SEM, the sample atomic number and the level of residual strain within it. The newer technique of orientation imaging in the transmission electron microscope, TEM, improves on this resolution limit by a factor of five to ten. The new technique is based on a novel procedure for determining the crystallography of separate small volumes in the sample by examination of a large series of dark field images. Each image is recorded for a different diffraction condition. This is achieved by using a computer to direct the electron beam onto the same area of the sample so that it covers all directions within a cone of semi-apex angle 3 degrees. Analysis of the intensity of the same point in each of the dark field images permits reconstruction of a diffraction pattern for that point providing the data to calculate its crystal orientation. The process is repeated for each point in the image. The Orientation Image Micrograph is constructed from the orientations so determined. The technique is shown to be capable of producing orientation micrographs of high spatial resolution for unstrained samples. For highly strained samples difficulties are encountered in accurately indexing the complicated diffraction patterns that are observed. Methods to improve the indexing procedures involve determining the sub-cell structure first from a comparison of patterns from adjacent pixels and then summing all patterns belonging to a single sub-cell. The resultant improvement in pattern quality permits more reliable determination of orientation. Examples of this procedure are taken from studies of deformed aluminum.     

Melt mixing of polycarbonate with multiwalled carbon nanotubes: microscopic studies on the state of dispersion

The focus of the paper is to investigate several issues related to the state of dispersion of multiwalled carbon nanotubes (MWNTs) in a polycarbonate (PC) matrix. A masterbatch of PC-MWNT (15 wt.%) was diluted with different amounts of PC in a small scale conical twin screw extruder (DACA Micro Compounder) to obtain different compositions of MWNT. In this system, electrical measurements indicated percolation of MWNT between 1.0 and 1.5 wt.%. We report TEM and AFM investigations of the state of dispersion of MWNT, in the entire volume of the matrix, in selected composites with compositions below (1 wt.% MWNT) and above the percolation threshold (2 and 5 wt.% MWNT). In addition, it was investigated if surface segregation of MWNT and flow induced orientation of nanotubes within the extruded strands had been occurred. It is found that the nanotubes dispersed uniformly through the matrix showing no significant agglomeration in the compositions studied. TEM micrographs seem to be able to detect the percolated structure of the carbon nanotubes. Furthermore, by comparing AFM micrographs from the core region and near to surface region no evidence of segregation or depletion of MWNT at the surface of the extruded strand was found. Comparison of TEM and AFM micrographs on surfaces cut along and perpendicular to the strand direction led to the conclusion that no preferred alignment had occurred as a result of extrusion. Aside from TEM technique, AFM is shown to be suitable to characterize the state of nanotube dispersion along with the issue of surface segregation and orientation of the nanotubes.