分光光度法测定车用甲醇汽油中的甲醇

建立了可见分光光度法测定甲醇汽油中甲醇含量的方法.实验结果表明,当甲醇含量在0-2.0mL/L时,吸光度与浓度能很好地遵循朗伯-比耳定律,相关系数为0.9934,该方法的平均加标回收率为96.9％,精密度实验M15和M20甲醇汽油的变异系数CV分别为1.1％和1.0％.     

Performances and design of ironless loudspeaker motor structures

This paper presents several kinds of structures of ironless loudspeaker motors. The proposed devices go from simple structures, in terms of manufacturing process, to structures in which the magnet rings can be stacked, with different magnetization directions or values. The structures are studied and compared according to their created induction level and uniformity across the coil displacement range, which are directly linked to the loudspeaker performances (force factor). The model used is the coulombian model of magnets to calculate the magnetic field created, therefore all the calculations are analytical. The paper shows that no structure is universal when it comes to the loudspeaker design: some are well adapted to micro displacements of the coil while other structures are adapted to large displacements.     

Energy transformation in biological molecular motors

Biological molecular motors transform the metabolic free energy into the directed movement. The physical principles governing this transformation are very different from the principles underlying the manmade macroscopic motors. Theoretical analysis shows that the internal thermal diffusion in motor proteins is a key element of the process, and the chemical energy performs no mechanical work directly but instead it is used for rectifying the diffusion. A few specific motor systems are considered to illustrate the general principle. The principle of rectified thermal diffusion has recently received a great support from the single-molecule studies.     

HL-2M 装置 300MVA 脉冲发电机组电气制动系统研究

为给 HL-2M 装置 300MVA 脉冲发电机组频繁启停和重大故障时快速停机提供保障，发电机组电气 制动系统采取电气制动和机械制动相结合的运行方式。介绍了 300MVA 脉冲机组电气制动的特殊性，对六相脉冲 同步发电机组电气制动进行了理论分析，确定了电气制动的主回路和控制方案。基于经验证的发电机模型，对正 常工况和极端工况下机组电气制动过程进行了动态模拟，确定了主要设计参数，制动励磁电压和制动电阻分别为 40V 和 0.1Ω。      

基于300MVA脉冲发电机组双闭环矢量控制建模及仿真

通过对 300MVA 脉冲发电机组的机械结构和电气特性的分析,利用现有的试验数据和铭牌数据对整 个机组的运行参数进行了等效计算,建立了基于 Simulink 的大功率异步电机双闭环矢量控制模型并进行了仿真分 析。通过调节转速环和电流环的比例积分(PI)参数改善电流、转矩波形质量。仿真结果表明,该调速系统具有较 好的动、静态性能,能够很好地满足机组的启动及运行要求。      

Characteristics of complex voluntary mandibular movements in the monkey before and after destruction of most jaw muscle spindle afferents

To study the role of proprioception in voluntary movement, two monkeys were trained to use their mandible to control the position of a lever that electronically loaded the jaw. They “tracked” stationary and moving targets both with and without visual feedback. Lesions of the tract of the mesencephalic nucleus of the fifth nerve, which destroyed most jaw muscle proprioceptors, did not interfere, even transiently, with the ability to perform the basic requirements of the jaw tracking tasks. There was an increase in low-frequency jaw tremor, and a small increase in the tracking error when the visual feedback signal was present, but these effects may have resulted from damage to other neural pathways. We conclude that muscle spindles are not necessary to perform well-practiced movements.     

A new quantitative analysis of significant timing differences between externally cued and self-initiated motor tasks in an fMRI study

It is generally accepted that the temporal resolution of blood oxygenation level dependent functional MRI is limited due to the inherent latency and longevity of the haemodynamic response. However, in this study we introduce a technique for measurement of timing differences from within the same brain region in two (or more) separate tasks that allows accurate determination of cortical timing differences 200 ms. Our technique, based on a novel use of linear regression analysis, is shown to yield accurate results both in simulated and experimental data. We show that cortical timing differences measured using fMRI are consistent with published electrophysiological results. Measurement of timing differences using this technique could prove a useful strategy for identifying neural network components in a wide range of cognitive paradigms.     

Walking Attainment in Very Low Birth Weight Infants in Japan

Objective: To clarify the corrected age of walking attainment in very low birth weight infants by birth weight and gestational age, and determine perinatal factors affecting the delay in walking attainment. Method: This was a longitudinal study. We investigated walking attainment and perinatal factors in 145 very low birth weight infants without neurological abnormalities (mean birth weight 1019.3 ± 299.7 g, gestational age 29.0 ± 2.9 weeks). The study infants were stratified by birth weight (group A: <1,000 g, group B: 1,000 g≤, <1,500 g) and gestational age (group I: <28 weeks, group II: 28 weeks≤, <37 weeks) and were compared using unpaired t-tests. Furthermore, we examined the perinatal factors that affect the delay in walking attainment using multiple regression analysis. Results: Of the walking attainment, infants in Group A were older than those in Group B (50th percentile, 15.8 vs. 14.7 months). Infants in Group I were older than those in Group II (50th percentile, 16.0 vs. 14.8 months). Using multiple regression analysis with walking attainment age as the dependent variable, the duration of mechanical ventilation was found to be significantly related. Conclusion: Very low birth weight infants with light weight and short gestational age have delayed walking attainment, and longer duration of mechanical ventilation increases the risk of delay.     

爪极高温超导电动机研制

自从发现高温超导材料以来,以美国为主的许多国家都非常重视高温超导电动机的研制,高温超导电动机技术取得了很大的成就。提出了一种新的爪极高温超导电动机模型,详细介绍了样机的原理、结构及设计参数。