Measurement of the rheological properties of polymer melts with slit rheometer. I. Homopolymer systems

Two slit dies have been designed, having aspect ratios of 10 and 20. Three melt pressure transducers were flush-mounted on the long side of the rectangular slot, along the longitudinal centerline of each die. The dies were then used to measure wall normal stresses along the longitudinal direction of polymer melts flowing through the thin slit. The polymeric materials investigated were high-density polyethylene, low-density polyethylene, polypropylene, and polystyrene. The measurement of wall normal stresses were used to determine the rheological properties of melts, namely, the melt viscosity from the slope of axial pressure profiles and the melt elasticity from exit pressures. The present study shows that the rheological properties determined from the slit rheometer are in good agreement with those from the capillary rheometer reported in the author's earlier papers. Therefore it may be concluded that a slit die also may be used as a means of characterizing polymeric materials by their viscous and elastic properties in the molten state.     

自含砷合碳难处理金矿中提取金的研究─Ⅰ.氨水脱砷-石灰加压氧化-氰化

针对甘肃省坪定金矿含金、砷高、金部分地赋存于脉石、脉石为碱性、属于难选难冶矿的特点，提出了氨水脱砷－石灰加压氧化－氰化新工艺．当原矿含金8．7g／t及13．0％砷时，砷可脱除95％，金可浸出85％．技术及经济指标预计均较满意．     

预加氢反应器的制造和检验

本文介绍了预加氢反应器的典型结构,分析了制造上的难点,有针对性地提出了解决难点的特殊工艺方案,记录了实际制造经验数据,对类似设备的制造有着重要的参考价值。     

Optical and surface properties of whey protein isolate coatings on plastic films as influenced by substrate,protein concentration,and plasticizer type

Composite film structures of common plastic polymers including polypropylene (PP) or poly(vinyl chloride) (PVC) with whey protein isolate (WPI) coatings may be obtained by a casting method. Optical and surface properties of the resulting WPI‐coated plastic films, as affected by protein concentration and plasticizer type, were investigated to examine the biopolymer coating effects on surface modification with polymeric substrates of opposite polarity. The measured properties involved specular gloss, color, contact angle, and critical surface energy. Regardless of the substrates, WPI‐coated films possessed excellent gloss and no color, as well as good adhesion between the coating and the substrate when an appropriate plasticizer was added to the coating formulations. The protein concentration did not significantly affect gloss of WPI‐coated plastic films. Among five plasticizers applied, sucrose conferred the most highly reflective and homogeneous surfaces to the coated films. The WPI coatings were very transparent and the coated films with various protein concentrations and plasticizers showed no noticeable changes in color. Experimental results suggest that WPI coatings formulated with a proper plasticizer can improve the visual characteristics of the polymeric substrate and enhance water wettability of the coated plastic films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 335–343, 2004     

Evaluation on steel bar corrosion embedded in antiwashout underwater concrete containing mineral admixtures

This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed for three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures and under different environments. The three series of antiwashout underwater concrete were: concrete constituted exclusively by ordinary portland cement (OPC), concrete composed by ordinary portland cement mixed with fly-ash in 20% ratio (FA20) and concrete with ground granulated blast furnace slag is mixed in 50% ratio (BFS50). And, the three different environments were: manufacture in the air, in tap water, and in artificial seawater.Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC manufactured in artificial seawater was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below − 350 mV after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm² and 0.258%. On the other hand, for the other specimens that are FA20 and BFS50, potential values below − 350 mV were observed later at 18 and 20 cycles, respectively.Results confirmed the expectation that mineral admixtures may be more effective in delaying the development of steel bar corrosion in antiwashout underwater concrete.     

Thermal and mechanical properties of the polymers synthesized by the sequential polymerization of propylene and 1‐hexadecene

The block copolymer of poly(1‐hexadecene) (PHD) and polypropylene (PP) was effectively synthesized by the sequential polymerization of propylene and 1‐hexadecene by using highly isospecific TiCl₃/Cp₂Ti(CH₃)₂ (Cp = cyclopentadienyl). The block copolymers had two separate melting temperatures of constituent blocks. The modulus of PHD–PP block copolymer was enhanced as the content of sequentially polymerized PP block was increased. The elongation at break showed positive deviation at the intermediate compositions from the simple additive values of constituent homopolymers. Shape memory effect which utilizes the crystalline PHD block as a reversible phase and the crystalline PP block as a fixed structure was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1709–1715, 2002; DOI 10.1002/app.10551     

合成氨装置中高温氢腐蚀问题探讨

探讨合成氨装置中的高温氢腐蚀问题,结合实际说明高温氢腐蚀的影响因素,提出预防高温氢腐蚀的措施.     

以合作学习为导向,探索中职计算机教学

随着我国教育模式的转变,在信息化的背景下,中国教育也逐步进入了信息化网络时代.为了提高计算机网络教学的发展,中职学校在计算机教学中进行了不断的探寻和研究,总结出通过合作学习的教学方式来提升中职计算机教学的教学质量.合作学习在中职计算机教学中的应用,使学生的学习应用能力与社会接轨,并锻炼学生合作意识,加强学生交流、分享能力.本文对合作学习在中职计算机教学中的应用进行研究分析,查找出其存在的问题,并给出了相应的解决策略.     

联通公司移动业务经营指标体系研究

电信行业在信息化的时代中发挥着重要的作用,随着电信行业重组以及4G移动牌照的发放,电信行业的竞争也更加激烈。联通公司作为电信行业中具有优势竞争力的企业之一,如何在新的时期确保持续、稳定的发展,增强企业竞争力,提高企业经营业绩,是要重点研究的问题。移动业务是联通公司的核心业务,移动业务经营指标体系是企业对自身业务发展进行评价的主要依据,研究联通公司移动业务经营指标体系,对于企业今后的发展具有重大意义。本文笔者将对联通公司移动业务经营指标体系构建的原则、体系内容进行详细论述,并说明如何应用移动业务经营指标体系。     

一种新型的WiMAX基站实时服务调度算法

为满足Wi MAX对Qo S的需求并克服MSIR调度算法存在的不足,本文提出了一种新型的基于截止期限最大信号干扰比的Wi MAX基站实时服务调度算法。这种算法根据链路质量和截止期限两个标准对数据包进行调度。首先从Wi MAX调度算法的Qo S架构出发,给出了信道模型;其次详细分析了本文提出方法的具体实现过程;最后,借助NS-2软件平台进行了建模与仿真。仿真结果表明,本文提出的方法减小了平均停留时间并有效提高了吞吐量和公平性指数,因此具有可行性和可靠性。