Performance of microwave synthesized dual solvent dope solution and lithium bromide additives on poly(ethersulfone) membranes

BACKGROUND: Generally the fabrication of polymeric membranes is a complicated and expensive process since it involves several steps. The preliminary preparation steps involve polymer drying and dissolution and is very time consuming and expensive. Currently, conventional electrothermal heating (CEH) is used to dissolve polyethersulfone in an aprotic solvent for membrane fabrication. Usually CEH requires 6 to 8 h at temperatures of 80 to 95 °C. This paper reports the fabrication and characterization of polyethersulfone (PES) asymmetric ultrafiltration membrane made from microwave (MW) synthesis casting solution consisting of various compositions of double solvents and lithium bromide (LiBr) additive. RESULTS: Homogeneous dual solvent dope solutions prepared via microware irradiation took only 1 h instead of the 7 h when prepared using CEH. The results also revealed that the membrane permeation and rejection rates, pore size and porosity were dependent on the ratio of LiBr to acetone. Membranes with LiBr kept at 2 and 3 wt% exhibited both high rejection and permeation rates with minimum pore sizes of 1.067 and 1.214 nm respectively. The presence of LiBr and the occurrence of chain scission were elucidated using Fourier transform infrared (FTIR) spectroscopy while its hydrophilic property was confirmed by water absorption and contact angle measurements. CONCLUSIONS: It was concluded that the microwave technique is capable of producing 1 L membrane solutions in less than 1 h. The membranes prepared from the microwave solutions show good rejection and permeation rates. Copyright © 2011 Society of Chemical Industry     

Extension of some MAP results to transient MAPs and Markovian binary trees

In this work we extend previous results on moment-based characterization and minimal representation of stationary Markovian arrival processes (MAPs) and rational arrival processes (RAPs) to transient Markovian arrival processes (TMAPs) and Markovian binary trees (MBTs).     

多选择软硬件划分问题的计算模型与动态规划算法

软硬件划分是软硬件协同设计的关键环节,划分的结果直接影响目标系统的设计质量。因此,对于一个给定的应用程序,为了使得目标系统快速执行且成本低廉,合理的划分策略十分重要。由于单个任务具有多种不同的硬件实现方式,与传统的单一硬件实现方式的软硬件划分问题相比,多选择的软硬件划分更能客观地反映现实应用。这导致问题的求解更具挑战性,它们已被证明是NP完全问题。基于多核处理器片上系统并针对任务图为二叉树的应用,建立了多选择软硬件划分问题的计算模型,并提出了解决该问题的动态规划算法。实验结果表明,当问题规模适中时,所提动态规划算法能够有效地获得精确解,并展示了算法的计算能力与硬件面积限制之间的关系。     

结合HSV与纹理特征的视频阴影消除算法

目的 在视频监控目标检测应用中,场景中的阴影会直接影响目标检测的准确度,因此阴影抑制算法研究显得尤为重要。目前广泛使用的是HSV（hue,saturation,value）阴影抑制方法,但是该方法存在由于亮度比值的阈值不稳定而造成将运动目标也检测为阴影的问题。针对该问题,本文提出了一种结合HSV与纹理特征的视频阴影消除方法。方法 首先将输入的图像使用传统的混合高斯模型建立背景并在灰度空间中提取前景,其次在HSV空间使用亮度比的阈值方法检测阴影,二者综合得到运动目标;针对由于亮度比值的阈值不稳定而导致的前景误检为阴影的问题,采用了LBP（local binary pattern）算子结合大津阈值（OTSU）提取部分运动目标。最后将LBP算子结合大津阈值提取的部分运动目标与HSV空间检测的目标两者相或,最终去除运动目标的阴影。结果 本文选用在CVPR-ATON和CAVIAR标准视频库中多个场景的阴影视频,将本文算法与SNP算法、SP算法、DNM1算法和DNM2算法进行对比仿真,实验结果表明本文算法在阴影检测率和阴影识别率的平均值上提升约10%。结论 本文提出的视频阴影消除算法结合了HSV与纹理特征,可以在不同的环境中有效地去除阴影,运动目标保留完整,可适用于智能视频监控、遥感图像和人机交互中。     

SIMILARITY‐BASED RETRIEVAL WITH STRUCTURE‐SENSITIVE SPARSE BINARY DISTRIBUTED REPRESENTATIONS

We present an approach to similarity‐based retrieval from knowledge bases that takes into account both the structure and semantics of knowledge base fragments. Those fragments, or analogues, are represented as sparse binary vectors that allow a computationally efficient estimation of structural and semantic similarity by the vector dot product. We present the representation scheme and experimental results for the knowledge base that was previously used for testing of leading analogical retrieval models MAC/FAC and ARCS. The experiments show that the proposed single‐stage approach provides results compatible with or better than the results of two‐stage models MAC/FAC and ARCS in terms of recall and precision. We argue that the proposed representation scheme is useful for large‐scale knowledge bases and free‐structured database applications.     

二元关系的性质测试及其复杂性分析

本文介绍了性质测试的基本原理,分析了用性质测试方法解决参数化问题的可行性,并将同构性质进行了参数化。研究了二元关系的性质测试以及参数化框架同构性质的测试问题,对固定的距离参数,证明了测试复杂性低于标准判定程序的复杂性。     

基于Gabor小波与LBP直方图序列的人脸年龄估计

提出了一种基于Gabor小波和局域二值模式(Local binary pattern,LBP)直方图序列的人脸年龄估计方法。首先对人脸图像提取多方向与多尺度的Gabor幅值域图谱(Gabor magnitude maps,GMMs);然后采用基于局部特征的LBP算子对GMMs编码,并对之分块,由各子块的直方图序列来描述人脸;为进一步降低人脸特征维数,再对人脸直方图序列特征应用主成分分析(PCA);最后使用支持向量机回归(SVR)的LOPO策略对人脸年龄库进行训练和测试。实验结果表明,该方法可以较为快速有效地对人脸图像进行年龄估计。     

基于局部Gabor变化直方图序列的人脸描述与识别

提出了一种在Gabor变换幅值域内提取局部变化模式空间直方图序列(histogram sequence of local Gabor binary patterns,简称HSLGBP)的人脸描述及其识别方法.鉴于Gabor特征对光照、表情等变化比较鲁棒,并已在人脸识别领域得到成功应用,首先对归一化的人脸图像进行多方向、多分辨率Gabor小波滤波,并提取其对应不同方向、不同尺度的多个Gabor幅值域图谱(Gabor magnitude map,简称GMM),然后在每个GMM上采用局部二值模式(local binary pattern,简称LBP)算子抽取局部邻域关系模式,最后由这些模式的区域直方图形成的序列来描述人脸.Gabor变换、LBP、空间区域直方图的采用使得该方法对光照变化、表情变化、误配准等具有良好的鲁棒性.而且,这种人脸建模方法不需要基于训练集合进行统计学习,因而不存在推广性问题.同时,进一步探讨了如何在分类器设计阶段与统计方法进行结合的问题,提出了统计Fisher加权的HSLGBP匹配方法.在通过FERET人脸库光照、表情和时间变化测试集上与已发表的实验结果进行对比,充分验证了该方法的有效性.     

The steady-State corrosion kinetics of two-phase binary alloys forming the most-stable oxide

The steady-state kinetics in the high-temperature oxidation of binary A-B alloys containing a mixture of the conjugated solid solutions of B in A (alpha phase) and A in B (beta phase) with exclusive formation of the most-stable oxide BO_v have been examined, assuming that the external scale grows on top of a subsurface layer of alpha phase. The results obtained are compared with the corresponding behavior of alloys which are single phase in the whole range of composition. Under identical values of all the parameters involved the concentration of B at the alloy-scale interface is smaller for two-phase than for single-phase alloys under the same concentration of B in the alloy as a result of the restricted flux of B through the alpha-phase layer. As a consequence of this, the two-phase alloys corrode more slowly than single-phase alloys and this difference increases as the solubility of B in the alpha phase decreases. Finally, the simultaneous formation of BO_v both externally and as internal oxide is more likely for two-phase than for single-phase materials.