Estimation of spatial-temporal gait parameters in level walking based on a single accelerometer: Validation on normal subjects by standard gait analysis

This paper investigates the ability of a single wireless inertial sensing device stuck on the lower trunk to provide spatial-temporal parameters during level walking. The 3-axial acceleration signals were filtered and the timing of the main gait events identified. Twenty-two healthy subjects were analyzed with this system for validation, and the estimated parameters were compared with those obtained with state-of-the-art gait analysis, i.e. stereophotogrammetry and dynamometry. For each side, from four to six gait cycles were measured with the device, of which two were validated by gait analysis. The new acquisition system is easy to use and does not interfere with regular walking. No statistically significant differences were found between the acceleration-based measurements and the corresponding ones from gait analysis for most of the spatial-temporal parameters, i.e. stride length, stride duration, cadence and speed, etc.; significant differences were found for the gait cycle phases, i.e. single and double support duration, etc. The system therefore shows promise also for a future routine clinical use.     

盐的某些神秘功能

除了调节身体的水量之外,盐还有其他许多重要功能。盐是一种强效的天然抗组胺剂,它可以缓解和消除哮喘症。在喝完一杯或两杯水后,把盐放到舌头上,它就和呼吸器一样有效,而且不会产生毒性。盐的这种使用方式,只适用于因干渴而处于危机状态的身体。在通常情况下,你应该把盐放到食物或水中。     

非洲主要河流的潜在作用

讨论了非洲几大水系在满足当地水资源和能源需求方面所起的主要作用。预计在21世纪末,低廉的水力发电或蓄能可以满足非洲大部分的能源需求。对非洲主要大型河流刚果河、赞比西亚河、尼日尔河及尼罗河的水电蕴藏量及其开发利用状况与产生的效益,开发过程中面临的诸多困难及应对措施等作了介绍。     

聚氯乙烯增塑糊用流变性能添加剂

增塑糊的流变性能是影响加工工艺与制品质量的重要参数。加工配方中加入流变性能添加剂可以调节不同剪切速率下的糊粘度,使之适应糊料的加工工艺和生产出合乎使用要求的制品。本文阐述了PVC增塑糊流变性能添加剂的作用、市场预测、发展概况与最新进展。     

挖掘游戏中震撼的音乐

2003年第2期的PCD曾介绍过如何观看和保存游戏中的精彩动画(编者注：《挖掘游戏中隐藏的动画》一文)，在下是《极品飞车6》的发烧友，但相对于游戏动画而言，我更喜欢它里面那些震撼的摇滚与Rap(每当放歌时，游戏画面的左下角就会显示相关歌曲的信息)!如果能把这些游戏歌曲都单独保存下来，     

集思广义 构造计量精英论坛平台——中国计量论坛年会专家谈

这次《中国计量》杂志社主办的中国计量论坛年会,我认为是个很好的形式,用民间的方式来研究讨论计量工作现在的形势、存在的问题、解决的方法。这样既可以互相交流情况和经验,又可以给官方提供些意见和建议。希望继续办下去。同时提几点建议:1.最好能请国家质检总局领导、计量司的领导参加会议,可以广泛听取意见,听取经验,为决策所用;2.议论主题应更集中,特别是研究那些当前突出的问题,以期论以致用;3.会议还可适当活些,如采取大小会结合的方式,可以畅所欲言,想说什么说什么,范围也更宽些;4.论坛可以把范围搞得稍宽些,既有系统内的,也有系统…     

Print your atomic force microscope

Progress in scanning probe microscopy profited from a flourishing multitude of new instrument designs, which lead to novel imaging modes and as a consequence to innovative microscopes. Often these designs were hampered by the restrictions, which conventional milling techniques impose. Modern rapid prototyping techniques, where layer by layer is added to the growing piece either by light driven polymerization or by three-dimensional printing techniques, overcome this constraint, allowing highly concave or even embedded and entangled structures. We have employed such a technique to manufacture an atomic force microscopy (AFM) head, and we compared its performance with a copy milled from aluminum. We tested both AFM heads for single molecule force spectroscopy applications and found little to no difference in the signal-to-noise ratio as well as in the thermal drift. The lower E modulus seems to be compensated by higher damping making this material well suited for low noise and low drift applications. Printing an AFM thus offers unparalleled freedom in the design and the rapid production of application-tailored custom instruments.     

Differential automatic zero-adjusting amplifier

A method is described for building a low-voltage-drift differential dc amplifier featuring automatic zero adjustment, a high input impedance, and a bandwidth of 10 kHz. This is achieved by an asymmetric two-step process between the input signal and ground. Bandwidth can be extended by the use of a second amplifier during the ground-sampling time. The amplifier can be made with standard electronic components. A major advantage of this method is that an existing amplifier can easily be converted into a low-voltage-drift amplifier by adding the essential elements of the described automatic zero-adjusting amplifier to its input stage. To illustrate the method a practical example is constructed featuring a drift of 0.2 microV/ degrees C.