新型排杂、降短绒刺辊锯条的设计与应用

设计了排杂、降短绒刺辊锯条,用常规试验方法对新型排杂、降短绒刺辊锯条所加工的生条进行了检测,结果发现,采用新型排杂、降短绒刺辊锯条的确有利于短绒的减少和棉结杂质的下降。也有利于落棉率的下降。采用加大齿深,底部负角设计,提高针布光洁度,弧形齿背,齿顶、工作边、背边处理成弧线等技术措施是新型刺辊针布能达到降低短绒目标的根本原因。     

Effect of ship motion on spinal loading during manual lifting

This study investigated the effects of ship motion on peak spinal loading during lifting. All measurements were done on a ship at sea. In 1-min trials, which were repeated over a wide range of sailing conditions, subjects lifted an 18 kg box five times. Ship motion, whole body kinematics, ground reaction forces and electromyography were measured and the effect of ship motion on peak spinal moments and compression forces was investigated. To investigate whether people time their lifts in order to reduce the effect of ship motion on back loading, trials were performed at a free and at a constrained (lifting every 10s) work pace. With increase of the (local) vertical ship acceleration, increased moments and compression forces were found. Furthermore, lifting at a free work pace did not result in smaller effects of ship motion on spinal moments and compression forces than working at a constrained work pace.     

Disturbance and recovery of trunk mechanical and neuromuscular behaviours following prolonged trunk flexion: influences of duration and external load on creep-induced effects

Trunk flexion results in adverse mechanical effects on the spine and is associated with a higher incidence of low back pain. To examine the effects of creep deformation on trunk behaviours, participants were exposed to full trunk flexion in several combinations of exposure duration and external load. Trunk mechanical and neuromuscular behaviours were obtained pre- and post-exposure and during recovery using sudden perturbations. Intrinsic trunk stiffness decreased with increasing flexion duration and in the presence of the external load. Recovery of intrinsic stiffness required more time than the exposure duration and was influenced by exposure duration. Reflexive trunk responses increased immediately following exposure but recovered quickly (～2.5 min). Alterations in reflexive trunk behaviour following creep deformation exposures may not provide adequate compensation to allow for complete recovery of concurrent reductions in intrinsic stiffness, which may increase the risk of injury due to spinal instability.

Statement of relevance: An increased risk of low back injury may result from flexion-induced disturbances to trunk behaviours. Such effects, however, appear to depend on the type of flexion exposure, and have implications for the design of work involving trunk flexion.     

Lower back muscle forces in pushing and pulling

Abstract

In the investigation of lower back stress, the muscle forces of the erector spinae and the rectus abdominis are often calculated using the two-dimensional biomechanical model. These muscle forces are used to estimate the compressive forces at L5/S1 disc This paper presents a study of the muscle forces predicted by a two-dimensional biomechanical model during pushing and pulling and myoelectric activity from the corresponding muscles. The goal was to investigate whether a simple two muscle torso model would reasonably estimate the muscle actions in pushing and pulling tasks. Six subjects participated in the experiment. EMG (rms) value was used as an indicator of muscle forces. The results show high correlation between the predicted muscle forces and the measured root-mean-square EMG values in trunk pushing and pulling (r²=0.93) and hand pushing and pulling (r²=0.96) in an erect posture with hips braced but low in hand pushing and pulling using a free posture (r²=0.37).     

Validity and reliability of the Spineangel® lumbo-pelvic postural monitor

Objective: to determine the reliability and the concurrent validity of the Spineangel^® lumbo-pelvic postural monitoring device. Methods: the dynamic lumbo-pelvic posture of 25 participants was simultaneously monitored by the Spineangel^® and Fastrak^TM devices. Participants performed six different functional tasks in random order. Within-task, within-session and between-day intraclass correlation coefficients (ICC(3,1), ICC(3,5), ICC(2,5), respectively) reliability were calculated for Spineangel^® measurements. Concurrent validity of the Spineangel^® was assessed by means of a Bland and Altman plot and by means of Pearson's correlation coefficient and paired t-test. Results: within-task, within-session and between-day ICC for the Spineangel^® were found to be excellent (>0.93). The Spineangel^® and Fastrak^TM pelvic measurements were found to have a good correlation (R = 0.77). Conclusion: the Spineangel^® is a reliable and valid device for monitoring general lumbo-pelvic movements when clipped on the belt or waistband of workers' clothing during various occupational activities.

Practitioner summary: The Spineangel^® can be used for assessing lumbo-pelvic posture during work or daily-life activities. This device was found to provide reliable and valid measurements for lumbo-pelvic movements. Further research is required to determine whether the use of this device is clinically relevant for patients presenting with low back pain.     

Active sitting with backrest support: Is it feasible?

Abstract

Ergonomics science recommends office chairs that promote active sitting to reduce sitting related complaints. Since current office chairs do not fulfill this recommendation, a new chair was developed by inverting an existing dynamic chair principle. This study compares active sitting on the inverted chair during a simulated computer-based office task to two existing dynamic office chairs (n?=?8). Upper body stability was analysed using Friedman ANOVA (p?=?.01). In addition, participants completed a questionnaire to rate their comfort and activity after half a working day.

The inverted chair allowed the participants to perform a substantial range of lateral spine flexion (11.5°) with the most stable upper body posture (≤11?mm, ≤2°, p?≤?.01). The results of this study suggest that the inverted chair supports active sitting with backrest support during computer-based office work. However, according to comfort and activity ratings, results should be verified in a future field study with 24 participants.

Practitioner Summary: This experimental laboratory study analyses the feasibility of active sitting with a backrest support during common office work on a new type of dynamic office chair. The results demonstrate that active sitting with a backrest support is feasible on the new but limited on existing chairs.     

复杂地质条件下调压室三维有限元参数反分析

在地下洞室施工过程的3维有限元模拟过程中,数值计算结果受到地应力场及岩体力学参数的影响。在参数反演过程中,地应力场和岩体力学参数对洞室围岩应力变形的大小影响过程非常复杂,要同时反演这两方面参数比较困难,因此依托复杂地质条件下柳坪水电站调压室工程,采用3维非线性有限元分析,把地应力场岩体力学参数分两步进行反演,首先利用洞室围岩变形之间的规律对地应力场进行反分析,岩体力学参数选取参考范围的中值,在获得计算模型的地应力场数值及分布规律后,再对岩体力学参数进行反分析,反演得到岩体的力学参数,得出微新围岩、断层、弱风化带、强风化带变形模量分别为19、0.45、4.5、2.25 GPa,泊松比分别为0.21、0.35、0.25、0.30。反分析位移与监测位移对比表明,平均相对误差符合计算精度要求,可为类似工程的研究、分析提供参考。     

计算机博弈中估值算法与博弈训练的研究

计算机博弈程序难以处理局面估值问题。为此,结合时间差分算法和反向传播神经网络,设计一种局面估值算法BP-TD(?),实现估值函数参数的自动调整。为提高博弈训练的性能,针对开局和中局,提出分阶段设置参数值的策略。以五子棋为应用背景,实现博弈系统RenjuTD。实验结果表明,该算法可使程序的博弈水平得到较大提高。     

基于图像分析的橘科植物病害识别技术

为实现橘科植物病害的计算机识别和病害程度的科学评价,提出通过分析病害图像,自动提取有效特征,设计分类器模型识别的方法．深入研究了怎样对病害图像进行自动增强处理、病斑分割、特征提取,以及怎样构建分类器模型等技术．最后以常见也容易混淆的五种柠檬病害为例,提取其病斑色调、纹理、形态三种特征向量,分别采用支持向量机和BP神经网络进行训练、测试．实验结果表明,该方法能很好识别植物病害类别,为科学防治和病害危害程度评价提供科学依据．     

极小的压电陶瓷变压器

本文介绍了一种新型的电子陶瓷材料——压电陶瓷材料．以及它在变压器领域中的应用。详细介绍了压电陶瓷变压器的结构、工作原理及广泛的应用。