Synthesis of amphiphilic heteroarm star‐shaped polymer via free radical polymerization using polyfunctional chain transfer agent and its self‐assembly behavior

Amphiphilic heteroarm star‐shaped polymers have important theoretical and practical significance. In this work, amphiphilic heteroarm star‐shaped polymer was synthesized by the use of polyfunctional chain transfer agent via sequential free radical polymerization in two steps. First, conventional free radical polymerization of methyl methacrylate (MMA) initiated by 2,2′‐azobis (isobutyronitrile) (AIBN) was carried out in the presence of polyfunctional chain transfer agent, pentaerythritol‐tertrakis (3‐mercaptopropinate) (PETMP). At appropriate monomer conversion, about two‐arm s‐PMMA having two residual thiol groups at the chain center was obtained. Second, the s‐PMMA obtained above was used as macro‐chain‐transfer agent for free radical polymerization of acrylic acid (AA). The heteroarm star‐shaped polymer with the hydrophobic PMMA segment and the hydrophilic PAA segment was obtained. The successful synthesis of heteroarm star‐shaped polymers, (PMMA)₂(AA)₂, was confirmed by ¹H‐NMR and its self‐assembly behavior in different solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

CHARACTERIZATION OF ZIRCONIA POWDER SYNTHESIZED VIA REVERSE MICROEMULSION PRECIPITATION

A two-reverse-microemulsion precipitation technique was applied to synthesize nanocrystalline tetragonal zirconia using H₂O solution/CTAB/hexanol as the microemulsion system. Two solutions of reverse microemulsion, one containing Zr⁴⁺ aqueous droplets and the other aqueous ammonia droplets with the same water/surfactant ratio, were prepared separately and mixed together to form a slurry of nanosized ZrO₂ precursors, which filled the matrix of the surfactant, CTAB. The precursors were recovered, calcined to form nanocrystalline zirconia powder, and then characterized by using a transmission electron microscope to determine the particle size, a scanning electron microscope to examine the microstructure of the zirconia powder, and an X-ray diffractometer to determine the crystal phase and crystallite size. It is concluded that the primary particle size of the precursor determines the transformation temperature of the precursor and the crystal structure of the calcined zirconia.     

输煤皮带转载点吸尘方式优化研究

采用Simple算法对输煤皮带转载点密闭罩内的煤尘浓度分布进行数值模拟,研究不同吸尘方式下密闭罩内吸尘罩的吸尘效果.采用单吸尘罩正向或侧向吸尘方式时,不同吸尘罩位置下密闭罩内溜槽转折处和密闭罩出口区域均出现煤尘积聚.相对正向吸尘方式,在溜槽转折处附近采用侧向吸尘,局部吸尘效果较好,同时下层密闭罩煤尘浓度相对较低.在密闭罩两端各设置1个吸尘罩,布置在溜槽转折处附近的吸尘罩采用侧向吸尘,布置在密闭罩出口区域的吸尘罩分别采用正向和侧向吸尘2种方式的组合吸尘方案时,上述区域煤尘积聚均得到缓解,密闭罩内吸尘效果显著提高.     

动态计算圆弧并面积的一个新算法

平面上以任意方式放置的Ｎ个圆所覆盖区域面积的计算问题称为圆弧并面积的计算问题，该问题不仅具有很强的应用背景，而且是计算几何，ＣＡＤ／ＣＡＭ和计算机图形学中的一个基础算法，本语文在给出有向多边形区域面积、约束圆弧所对圆心角计算公式的基础上 一个基于圆弧求交、平面有向我边形面积、扇形面积计算的动态计算圆弧并的一个新算法，该算法具有计算精度度     

Highly ordered C60 films on epitaxial Fe/MgO(0 0 1) surfaces for organic spintronics

Hybrid interfaces between ferromagnetic surfaces and carbon-based molecules play an important role in organic spintronics. The fabrication of devices with well defined interfaces remains challenging, however, hampering microscopic understanding of their operation mechanisms. We have studied the crystallinity and molecular ordering of C₆₀ films on epitaxial Fe/MgO(0 0 1) surfaces, using X-ray diffraction and scanning tunneling microscopy (STM). Both techniques confirm that fcc molecular C₆₀ films with a (1 1 1)-texture can be fabricated on epitaxial bcc-Fe(0 0 1) surfaces at elevated growth temperatures (100–130 °C). STM measurements show that C₆₀ monolayers deposited at 130 °C are highly ordered, exhibiting quasi-hexagonal arrangements on the Fe(0 0 1) surface oriented along the [1 0 0] and [0 1 0] directions. The mismatch between the surface lattice of the monolayer and the bulk fcc C₆₀ lattice prevents epitaxial overgrowth of multilayers.     

1000MW直接空冷机组排汽管道内湿蒸汽的数值模拟

排汽管道是空冷岛重要的系统和部件,其管线布置方式是否合理,管内压降及蒸汽流量分配均匀性是否满足设计和使用要求,影响到空冷凝汽器的运行效率和冬季的防冻维护,是直接关系到发电机组经济运行和安全的大问题。应用ANSYS、FLUENT等计算流体力学软件(CFD)对某1000MW直接空冷机组排汽管道内的湿蒸汽进行了数值模拟,并对模拟结果进行了简要分析、研究。为直接空冷机组排汽管道的设计选型提供了参考依据,并对直接空冷机组排汽管道的进一步优化设计提供帮助。     

Formaldehyde OTFT Sensors Based on Airbrushed Different Ratios of P3HT/ZnO Films

The formaldehyde (HCHO) detecting at room temperature is of great significance. Different ratios of P3HT/ZnO composite films (3:1, 1:1, and 1:3) were deposited on the organic thin film transistor (OTFT) by spray-deposition technology, and the electrical properties and HCHO-sensing properties of all the prepared OTFT devices were measured by Keithley 4200-SCS source measurement unit. The results show that the OTFT sensor based on the P3HT/ZnO films with the ratio of 1:1 exhibited the best output and transfer curves. Different changing tendency were observed with the increase of ZnO proportion when exposed to HCHO at room temperature, and the device with the ratio of 1:1 behaved a good response and recovery characteristics.     

Determination of seven preservatives in cosmetic products by micellar electrokinetic chromatography

A micellar electrokinetic chromatography method using cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, coupled with UV–Vis detection, was developed for the simultaneous determination of seven preservatives, including methyl‐, ethyl‐, propyl‐ and butyl‐paraben and phenol, phenoxyethanol and resorcinol. The method involved optimizing the pH of the phosphate buffer and concentrations of CTAB, ethanol and 2‐hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD). The preservatives were well separated using optimum conditions and separated within 10 min at a separation voltage of ?12.5 kV with the 1.0 mM phosphate buffer (pH 7.0) containing 90 mM CTAB, 25 mM HP‐β‐CD and 10% (v/v) ethanol. Satisfactory recoveries (84.1–103.0%), migration time (RSD < 3.1%) and peak area (RSD < 4.5%) repeatabilities were achieved. Detection limits of the preservatives were between 0.31 and 1.52 μg mL^?1 (S/N = 3, n = 5). The optimized method was successfully applied to the simultaneous determination of these preservatives in 10 commercial cosmetic products.