Surface crosslinking of high‐density polyethylene beads in a modified plasma reactor

High‐density polyethylene (HDPE) beads were successfully surface‐crosslinked in a modified plasma reactor. The modified plasma reactor treats large amounts of beads, which are uniformly surface‐crosslinked. In this study, effects of the gas pressure, radio‐frequency (RF) power, and the treatment time on the degree of surface crosslinking were systematically investigated. Degree of surface crosslinking was measured by solvent extraction method (boiling xylene method, BXM). The gel content of plasma‐treated HDPE increases from 0.0 to 1.05% within 10 min at 100 mTorr, 200 W. FTIR and DSC analyses show that the crosslinked layer after plasma treatment is limited only at HDPE surface without changing the bulk thermal property of HDPE. Through the analysis of FTIR, it was confirmed that main peaks corresponding to CH₂ bands were decreased and two peaks corresponding to CF₂ and CF₃ were observed after plasma surface modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2921–2929, 2002; DOI 10.1002/app.10295     

Has water-saving irrigation recovered groundwater in the Hebei Province plains of China?

This study performed a quantitative evaluation of the impact of water-saving irrigation on the groundwater regime in the Hebei Province plains area. In this work, the change in groundwater regime and the contributions of precipitation and water-saving irrigation development were investigated. The results indicate that the groundwater overdraft has been mitigated to some extent, mainly due to changes in precipitation and the implementation of water-saving irrigation, with contributions of 64.3% and 35.7%, respectively, when considering only these two factors. Water-saving irrigation is accepted as an important means for reducing groundwater depletion, but should be used in conjunction with other measures.     

A Flood Forecasting Model that Considers the Impact of Hydraulic Projects by the Simulations of the Aggregate reservoir’s Retaining and Discharging

The hydraulic projects, such as reservoirs, ponds, and paddy fields, have a marked influence on the generation of floods, causing a number of difficulties where hydrological forecasting is concerned. To consider the influence of the hydraulic projects in hydrological forecasting, a modified TOPMODEL is presented in the paper, based on the simulation rules of the aggregate reservoir’s retaining and discharging (ARRD). In the new purposed model, termed as ARRD-TOPMODEL, the hydraulic projects are first aggregated as an equivalent reservoir, then the simulation rules of the aggregate reservoir’s retaining and discharging are determined, finally, the simulation rules are combined with an original TOPMODEL model calibrated using the floods not influenced by the hydraulic projects for flood forecasting. The ARRD-TOPMODEL was tested on the upstream of Wudaogou station basin in Northeast China. The results show that compared to the original model, the qualified rate (i.e., the ratio of the number of floods that meet acceptable criteria and the total number of floods) of runoff forecasting was increased from 73% to 100%. The problems that the overestimation of the runoff at beginning of flood season and after a long drought, as well as that the underestimation of the large flood in middle flood season are both solved, and the flood processes predicted by the new model are more consistent with the observed ones. All of these demonstrate that the newly developed model is superior to the original one and the simulation rules of the aggregate reservoir’s retaining and discharging are capable of accurately accounting for the influence of the hydraulic projects on the floods.     

聚醋酸乙烯乳液缩醛化的改性研究

本文介绍了为提高聚醋酸乙烯乳液稳定性、耐水性和防冻性而进行缩醛化改性的原理，并确定了最佳工艺条件即甲醛与聚乙烯醇的配比为０．４５～０．５０。     

趋磁性细菌的培养及其在污水处理方面应用的研究

介绍了趋次性细菌的磁特性和生态分布,对趋磁性细菌培养方法的研究进行了练述,并根据文献资料对趋磁性细菌进行了驯化培养,最后对趋磁性细菌在处理含重金属离子有机废水方面的应用前景进行了展望.     

聚醚多元醇中环状齐聚物的去除(续)

(接上期第 2 3页 )3　膜分离Doraietal[16] 通过超滤除去低相对分子质量级份 ,使聚醚多元醇 ,尤其是聚四氢呋喃多元醇 ,具有较窄的分布 (Mw∶Mn=1 .2～ 1 .8)。该方法通过对多分散的熔融聚合物实施物理分级 ,达到降低相对分子质量分布的目的 ,可使最终产物的相对分子质量为 40 0～ 40 0 0 ,分散度为 1 .2～ 1 .8。该方法首先需要准备 1套交叉流动的膜分离系统 ,采用渗透膜或半渗透膜 ,膜的一边是滞留物 ,另一边是超滤液。然后 ,在起始聚合物的熔点以上 ,分解温度以下 ,且温度不大于膜的熔融和分解温度 ,将起始聚合物熔融 ,并流入该系统中…     

吉林省中小流域经验模型的应用探讨

由于中小河流水文站点多数都属于无资料站,所以用传统的经验相关或者流域水文模型有一定难度。吉林省水文水资源局水情预报中心的工作者根据多年预报经验总结提出吉林省中小流域经验模型。该方法主要依据流域特征以及降雨和洪峰流量的关系,推算流域产流;再根据时段降雨按照产流过程叠加处理,概化流量过程,进行洪水预报。属于产汇流一体的流量过程计算模型。     

地表水质监测模型中的几种人工智能方法

重点对地表水质预测模型的几种人工智能方法进行了评述,具体说明了BP神经网络水质预测模型、地表水COD灰色预测模型、时间数列预测方法及WASP5模型系统等方法的原理和特点.并提出地表水质预测模型WASP5与GIS系统集成的趋势,建立水质自动监测系统是我国水质现状和社会发展的需要,并分析了发展水质自动检测系统的方法及可行性.     

对甲基苯甲酸液相催化氧化动力学

研究了以醋酸钴和醋酸锰为催化剂、氢溴酸为促进剂,在169～192 ℃下对甲基苯甲酸(p-TA)的液相氧化反应动力学.采用幂函数动力学模型对实验数据进行了拟合.结果表明,对甲基苯甲酸液相氧化反应是串联反应,甲基苯甲酸和中间产物对羧基苯甲醛的反应级数均为1.拟合得到的活化能数据表明对甲基苯甲酸氧化为整个反应的控制步骤.利用该动力学模型能够成功预测186 ℃下液相组分随时间的变化趋势.实验表明,当金属离子的配比满足[Co2 ]/[Mn2 ]为3∶1时,催化剂具有最高的活性.     

高性能热塑性树脂基复合材料的研究进展

近些年来,纤维增强热塑性树脂基复合材料已逐步发展成为复合材料中一个高性能、低成本的新型材料家族。本文主要介绍了各种高性能工程塑料和增强纤维的发展,连续纤维增强热塑性树脂的浸渍工艺及成型工艺,最后还介绍了热塑性纤维复合材料的发展趋势。