连续加工路径的进给速度规划算法研究

为了实现数控系统连续轨迹的速度规划,本文提出了混合进给速度的规划方法.此方法通过建立转弯处加工路径和加工误差的数学模型,实现了转弯处进给速度的控制.实验结果表明,这种方法不仅可以极大的提高机床的加工效率,减小由于路径转弯剧烈引起的机床震动,从而大大提高工件的加工质量.混合进给速度的规划方法保证了加工精度和加减速的稳定性.     

玻璃纤维纱线强力与捻度的关系

测试了玻璃纤维纱线的断裂强力、捻度与线密度等物理性能指标,建立了玻璃纤维纱线强力与捻度的回归曲线,并讨论了玻璃纤维纱线的强力与捻度的关系．结果表明,玻璃纤维纱线的强力先随着捻度的增加而升高,然后又随着捻度的增加而降低;玻璃纤维纱线具有临界捻度．这对生产上精选设计及快速调整捻度具有指导意义．     

马克隆值对成纱质量影响的灰色聚类分析

马克隆值是原棉细度和成熟度的综合指标,其大小影响成纱质量.对不同马克隆值的原棉进行了单唛试纺,并测试其成纱质量的各个指标,通过灰色聚类的方法进行分析.结果表明,在其他条件不变的情况下,棉纤维马克隆值在3.7～4.3时成纱质量最好.在纺纱过程中,根据成纱的用途,必须合理配置马克隆值的原棉,才能纺制出符合产品质量要求的纱线.     

现代细纱前后牵伸区附加摩擦力界的布置与探讨

探讨了细纱前牵伸区新型上销、下销、附加压力棒隔距块及后区压力棒、皮圈牵伸的纺纱原理及效果。测试分析了细纱前区新型上销、下销及附加压力棒牵伸、细纱后区附加摩擦力界装置与普通牵伸纺纱质量的差异,总结了前后区附加摩擦力界对浮游纤维的控制特点,并分别在JC9.7tex上和JC14.5tex进行了试验对比。结果表明:这些新型纺纱装置能加强对细纱前区浮游纤维的控制,有利于纺纱质量的提高。     

Blended Learning to Increase Student Satisfaction: An Exploratory Study

Undergraduate nursing research courses are often difficult to teach due to the challenging content and lack of student satisfaction. To address this issue, two nursing instructors and a librarian embedded online discussions into an accelerated format, introductory nursing research course. The study was conducted over two semesters with two different instructors. The researchers investigated if using the blended learning strategy of discussion boards enhanced the learning experience and tested their theory with two measures: a weekly qualitative questionnaire and a post-study survey. Results suggested that asynchronous online discussions increased student satisfaction in introductory nursing research course work.     

The friction twisting of continuous filament yarns

An overview of friction twisting of continuous filament yarns is presented. Starting from the older pin twisting process, the development of friction twisting is traced up to the present day when yarn rotational speeds of 5 million r/min are possible. One of the main problems encountered in friction twisting is the generation of a normal force between yarn and rotating disc sufficient to supply a frictional force to twist the yarn, without inducing excess tension in it. Solutions to this are presented leading to an analogy with the simple capstan, from which relations are derived for the friction between yarn and disc and for the tension in the yarn. Finally, a current development for friction twisting using belts is described.     

Precise and reproducible deposition of thin and ultrathin carbon films by flash evaporation of carbon yarn in high vacuum

A simple, small device and its use for reproducible flash evaporation of carbon yarn in high vacuum are characterized. Using this flash evaporator, carbon films of any thickness up to 20 nm can be deposited without spark generation under minimized photon radiation, and with an accuracy better than ±0·2 nm. The films have less background structure (imaged in phase contrast) than conventionally rod evaporated films and are therefore suitable for many kinds of thin and ultrathin carbon film applications in electron microscopy, e.g. as backing for formvar films or sections, as isolating carbon layers for autoradiography, as ultrathin films (floated from mica) for support of macromolecules to be metal shadowed and as support and cover for negative staining of various specimens by the sandwich technique.     

Experimental investigation on the effect of alkanes blending on performance,combustion and emission characteristics of four-stroke diesel engine

In this experimental investigation, an attempt was made to increase the performance and reduce the emission by adding alkanes such as n-pentane and n-hexane separately at different proportions, such as 4%, 6% and 8% by volume, with diesel. The performance analysis reported that, at full load, the brake thermal efficiency was increased by 3.605%, 3.170%, 4.305%, 4.394%, 5.336% and 6.173% for the blending of 4% n-pentane, 6% n-pentane, 8% n-pentane, 4% n-hexane, 6% n-hexane and 8% n-hexane with diesel, respectively. The emission test concluded that the smoke density was increased by 9.915%, 9.905%, 6.325%, 9.573%, 6.154% and 5.983% for the blending of 4% n-pentane, 6% n-pentane, 8% n-pentane, 4% n-hexane, 6% n-hexane and 8% n-hexane with diesel, respectively. The NO_x emission was decreased by 8.265%, 8.674%, 17.430%, 5.401%, 5.810% and 7.529% for the blending of 4% n-pentane, 6% n-pentane, 8% n-pentane, 4% n-hexane, 6% n-hexane and 8% n-hexane with diesel, respectively.     

以MDEA为主体的混合胺溶液吸收CO2研究进展

综述了近年来乙醇胺、二乙醇胺、哌嗪、碳酸酐酶以及离子液体与N-甲基二乙醇胺的混合溶液用于CO2吸收的研究进展;分析了混合溶液的吸收机理和CO2吸收的动力学;讨论了混合溶液组成、体系温度、压力等对吸收性能的影响;并对该法未来的研究方向和发展前景进行了展望.     

职教云在混合式教学中的应用研究——以高职电子商务专业“摄影摄像实务”课程的教学模式改革为例

“摄影摄像实务”课程是广东工程职业技术学院电子商务专业开设的一门专业拓展课,主要培养学生摄影摄像的实践操作技能、审美能力、创作能力和职业素养。传统的课堂教学模式对学生来说比较枯燥、抽象,不利于调动学生学习的积极性,教学效果不尽如人意。因此,为了打破传统教学模式的局限性,文章针对本课程特点,研究设计了教学模式改革方案——利用职教云进行混合式教学,以提高教学质量。