Thermal‐initiating potentialities of vinyl polyperoxides: Transmutation of block‐into‐block copolymer and an exploratory investigation of surface texture and morphology

This article describes the first comprehensive study on the use of vinyl polyperoxides, namely, poly(α‐methyl styrene peroxide) (PMSP) and poly(styrene peroxide) (PSP), as thermal initiators for the synthesis of active polymers, PMSP–PS–PMSP/PSP–PS–PSP, by free‐radical polymerization with styrene. The active polymers have been characterized by ¹H NMR, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography analysis. The PMSP–PS–PMSP/PSP–PS–PSP is further used as the thermal macroinitiator for the preparation of another block copolymer, PS‐b‐PMMA, through the reaction of the active polymers with methyl methacrylate. The mechanism of the block copolymer formation is discussed. Having established the scanning micrograph details of the homopolymer phases, we analyze the surface features and morphology of the block copolymer. Furthermore, the distinction in appearance is highlighted with a view toward strengthening the chemistry with the structural appearance in materials processed differently. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3665–3673, 2000     

Self-Assembled Multistable Scattering Mode for Versatile Energy-Saving Smart Windows

Smart windows are crucial to dynamic control over light transmission to fulfill various demands in energy saving, privacy, and information display; however, most present technologies still perform a single function (often tint or haze adjustment) and require continuous electricity for operation. In this study, novel self-assembled ionic liquid crystals (ILCs) doped with negative cholesteric liquid crystals (CLCs) to offer electrically switchable and stable scattering-mode light modulators are presented. The novel smectic A phase based on the ILCs exhibits high solubility in the adopted nematics, enhancing the LC device's performance in several ways, including improved homogeneity, stable alignment quality, prolonged stability, and simplified fabrication. The LC device can potentially offer a dynamically rapid switching function between stable transparent (imperfect fingerprint textures) states and stable scattering (focal conic textures with small domains) states by using external stimuli and highly maintained multistable states for prolonged periods, even when the external stimuli are removed. The LC device also offers polarization-independent scattering and transparent-mode LC light modulators, low operating voltage, excellent contrast, and broad viewing angles. Its versatility and outstanding field-off stability make it ideal for various applications such as smart lighting, building climate control, energy-saving displays, and augmented reality (AR) glasses.     

基于小波-双马尔可夫随机场的纹理分割

传统高斯金字塔马尔可夫随机场模型仅仅捕捉图像低频信息,纹理分割效果不太理想.根据纹理图像小波分解后各频带的统计性质和层次关系,优化频带选取,提出了一种变形小波结构,建立了融合这种结构上尺度内部和尺度之间关系的双马尔可夫随机场模型,引入了一种近似最大联合概率分割算法,并从理论上分析了该算法的合理性.实验表明,与基于高斯金字塔马尔可夫随机场模型的分割方法相比,该算法分割质量明显提高;并且,对模型中自由参数的选取进行比较,证实它们在给定区间上的选择具有鲁棒性.     

Polymers of carbonic acid. XXIV. Photoreactive,nematic or cholesteric polycarbonates derived from hydroquinone-4-hydroxybenzoate 4,4′-dihydroxychalcone and isosorbide

Numerous polycarbonates were prepared by means of “diphosgene” in pyridine using hydroquinone 4-hydroxybenzoate (HQHB) as mesogenic diphenol. In addition to the homopolycarbonate, binary copolycarbonates of HQHB and 4,4′-dihydroxychalcone (DHC) with varying molar composition were prepared. A series of ternary copolycarbonates were obtained by incorporation of isosorbide. Furthermore, an alternating copolycarbonate of HQHB and isosorbide was synthesized. All polycarbonates were characterized by inherent viscosities, elemental analyses, IR-, ¹H-NMR, and ¹³C NMR spectroscopy, by WAXS powder patterns DSC measurements, and optical microscopy with crossed polarizers. The homopolycarbonate of HQHB and most binary copolycarbonates were semicrystalline materials forming an enantiotropic nematic melt. Particularly noteworthy is the finding that the alternating copolycarbonate of HQHB and isosorbide forms a broad cholesteric phase despite the unfavorable stereochemistry of isosorbide. The ternary copolycarbonates containing isosorbide formed a cholesteric melt and a Grandjean texture upon shearing. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1611–1619, 1997     

辅以纹理特征的植被分类方法研究

纹理是遥感影像处理和计算机视觉领域中的重要研究内容,在植被遥感中有着非常广泛的应用前景。本文主要讨论在面向对象,多尺度分割的基础上,分别基于光谱信息和纹理特征的最邻近分类法提取南京某新开发区的植被信息。研究结果表明,与传统的基于光谱信息和基于象元特征的分类法相比,辅以纹理特征的最邻近分类法的总体精度分别提高了6.36%和1.16%。     

基于信息熵的局部二值模式手指静脉识别

为进一步提升手指静脉识别算法的识别率与识别速度,在图像处理阶段,提取出手指图像的感兴趣区域(region of Interest, ROI),减少手指周围区域的干扰。为提升识别率,在局部二值模式 (local binary patterns, LBP)的基础上,引入像素邻域之间的关系,增强LBP的识别性能;然后将信息熵与改进型LBP结合得到新的ELBP特征,最后采用主成分分析(principal component analysis,PCA)降维,以减少识别时间,去除冗余特征。通过对比欧氏距离与曼哈顿距离构建的分类器,与其他主流特征比较,验证算法的识别性能。在SDUMLA数据库与天津市智能实验室采集指静脉图像数据库上,保证了算法的识别速度前提下,分别取得了99.53%、99.84%的识别率,与其他识别算法相比识别率有明显的提高。     

岩石风化程度对土岩双元基坑变形的影响

土岩双元基坑是指开挖深度范围内,上部为土层,下部为岩层的基坑。由于下部岩层的力学性质与土层差异较大,因此传统纯土体的一元结构基坑相关理论与经验对该类基坑的适用性较差。本文利用FLAC3D有限差分软件,建立不同岩石风化程度的土岩组合基坑计算模型,研究不同岩石风化情况下土岩双元基坑的变形规律,并用连续-离散耦合模型模拟土+破碎岩石基坑失稳过程。结果表明：若岩层完整,最大水平位移出现在土层中,岩层中水平位移很小;若岩层为破碎状,最大水平位移有可能出现在岩层中;岩层中的粘土夹层也可能是基坑最大变形出现的部位;破碎岩石内部的破坏是同土层同步发育的,最终二者一起发生整体滑移破坏。了解基坑的变形规律,有助于针对性地采取加固措施,对破坏区域的细观研究为基坑支护设计提供了依据。     

New polymers of carbonic acid. XXV. Photoreactive cholesteric polycarbonates derived from 2,5‐bis(4′‐hydroxybenzylidene)cyclopentanone and isosorbide

Several binary copolycarbonates were prepared by polycondensation of 2,5‐bis(4‐hydroxybenzylidene)cyclopentanone, BHBC, with methylhydroquinone, MHQ, hydroquinone 4‐hydroxybenzoate, HQHB, or isosorbide. Furthermore, five ternary copolycarbonates were prepared based on the aforementioned monomers. All polycondensations were conducted in pyridine with trichloromethyl chloroformate as condensing agent. All polycarbonates were characterized by elemental analyses, viscosity and DSC measurements, IR and ¹H‐ and ¹³C‐NMR spectroscopy, optical microscopy, and the WAXS powder pattern. All isosorbides containing binary and ternary copolycarbonates were found to form a cholesteric melt, but only three of them were capable to form a stable Grandjean texture upon shearing. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1125–1133, 1999     

不同冷藏条件下大黄鱼质构和风味变化的研究

为探讨贮藏温度和储藏时间对大黄鱼质构和风味变化的影响, 运用电子鼻和顶空固相微萃取气质谱联用法(HS-SPME-GC-MS)分析在4, -20, -80℃的3种条件下, 储藏不同时间(1, 3, 5, 7, 30, 60, 90d)时大黄鱼肉的挥发性风味变化, 并应用质构仪测定大黄鱼肌肉质构特征参数. 结果发现, 4℃条件下贮藏3~7d, 其质构参数值明显相对于-20℃条件偏大(主要为硬度、韧性、回复性和黏着性差异显著); -20℃和-80℃条件下储藏30~90d, -80℃条件下贮藏大黄鱼肉质构特性优于-20℃条件; 而且, 随着贮藏温度降低, 大黄鱼挥发性物质种类减少. 在-20℃和-80℃条件下, 大黄鱼挥发性成分相对较少, 且各成分占总峰面积的相对含量变化不明显, 主要挥发性物质为烃类和醛类; 在4℃条件下贮藏的鱼肉, 其挥发性组分复杂且相对含量变化明显. 结果表明, 低温冻藏能有效保留大黄鱼肉质构特性和风味.