Manufacture of carbon fibers from polyacrylonitrile precursors treated with CoSO4

Free‐radical solution copolymerization of itaconic acid and acrylonitrile was carried out in DMSO using azodiisobutyronitrile as an initiator, changing the feed rate of itaconic acid. The resulting polymerization solution was spun to form polyacrylonitrile (PAN) precursors of carbon fibers. The precursors were treated with a CoSO₄ aqueous solution on‐line. The structure and properties of untreated and treated PAN precursors and the resultant carbon fibers were characterized by SEM and TEM, a stabilization process, etc. It is suggested that CoSO₄ acts as a catalyst in the formation of a ladder structure and reduces the temperature of cyclization, and the carbon fibers developed from treated PAN fibers showed improvement in the tensile strength and the Young's modulus. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 153–158, 2002     

HSLA-80/100钢的焊接

对ＨＳＬＡ－８０／１００钢的焊接性、焊接材料及焊接工艺进行了综述，并指出了现存在的主要问题。     

生态城市与水利现代化

对天津及其滨海新区生态城市水利建设进行了分析。研究了在淡水资源极度匮乏的条件下,有效开发利用非常规水资源的必要性、重要性和现实性。认为天津市对水资源应遵循节水、治污、高效配置,妥善处理生活、生产、生态之间的关系,力求平衡调配。供水水源应是多元的,增加非常规水资源(污水、海/咸水、雨/洪水)的利用,同时增加可用地下水,外调来水等,逐步进入可持续发展配置。     

用于频率合成器的低损耗声表面波滤波器

简述了产生声表面波滤波器插入损耗的主要机理和获得低损耗的原则；介绍了根据此原则对１００～５００ＭＨｚ５种滤波器的研制过程和结果。实验表明，采用镜像阻抗连接换能器结构可达到３～４ｄＢ的低损耗，并成功地应用于频率合成器中。     

微波BJT超宽带低噪声放大器的设计

本文给出了一种频带覆盖达１０－１６００ＭＨｚ的微波ＢＪＴ超宽带低噪声放大器的设计方法，从微波ＢＪＴ的噪声模型出发，通过拟合５０Ω源阻抗下微波ＢＪＴ的噪声系数ＮＦ５０和Ｓ参数来提取其噪声参数，然后根据增益，噪声及驻波比要求优化设计放大器，使放大器在超宽带范围内获得平坦增益和低噪声，本文所给出的微波ＢＪＴ惨数提取及放大器优化设计方法已由实验结果所验证。     

PAN共聚纤维的热氧化研究

本工作采用连续式实骏装置与方法,借助力学测试、X射线衍射、元素分析、红外光谱等技术,系统地研究了PAN共聚纤维在连续热氧化过程中化学、结构、性能间的联系,亦对PAN基碳纤维力学性能提高的途径进行了探讨。研究结累表明:在热氧化过程中,PAN共聚体系的热化学反应主要发生在250℃左右;其间纤维的序态结构变化剧烈,易使纤维产生结构缺陷,进而影响热氧化纤维力学性能的变化。     

Sunflower Head Residue Pectin Extraction as Affected by Physical Conditions

Effects of extraction pH, temperature, and time on yield and quality of pectin from sunflower heads (Interstate cultivar) were investigated. The low-methoxyl pectin was extracted, using 0.75% sodium hexametaphosphate at pH 3, 4, and 5 and at 75, 85, and 95°for 20, 40, and 60 min, respectively. Yield, molecular mass, and firmness of jellies of the pectins were determined. Three-way statistical analysis on yield, molecular mass and gel firmness showed strong interactions among pH, temperature and time. Highest yields were obtained at pH 5, 95°for 20 min and pH 4, 85°for 40 min. Pectin extracted for 40 min at pH 3 and 4 and at 85°and 75°C, respectively, had the highest molecular mass. Gel firmness of sunflower pectin prepared at pH 5.4 was higher than that of a commercial citrus pectin.     

耐高温微生物驱油提高低渗透油藏采收率先导性试验

胜利油田东辛高温低渗透油藏含蜡高,常温微生物无法存活,针对这一问题,引进美国NPC公司耐高温菌种,在Y6-16井组开展高温低渗油藏微生物驱油提高采收率研究和现场试验。施工后Y6-16井日增注52m3,表皮系数由施工前的2.069减小为施工后的-6.31,油层污染得到较好改善;原油含蜡量、胶质沥青质含量降低,轻质组分增加,重质组分降低;井组采收率提高5.09个百分点。     

叔丁醇氧化产物的气相色谱分析

介绍了用气相色谱分析叔丁醇两步氧化制甲基丙烯酸液相产物的组成，该分析方法能够分析液相产物中的醛类，酮类和酸类化合物共计9个组分，C2－C4有机酸无记忆效应，其色谱峰不拖尾，该分析方法的相对标准偏差≤8．5％，回收率在94．5％－103．7％之间，是一种快速，准确，操作简单的分析方法。     

回火处理对高碳冷拔钢丝强度和塑性的影响

研究了６５钢冷拔钢丝在５００℃不同时间回火时的抗拉强度和延伸率的变化。试验结果发现，在回火初期，抗拉强度首先增长，然后随口火时间的延长连续降低，而延伸率始终在增长，增长速度是先快后慢。这种行为可归因于第一内应力的消除和ε－碳化物在形变铁素体中的析出以及后来再结晶的发生。