目标肌肉神经分布重建对大鼠幻肢痛的影响及神经分布研究

目标肌肉神经分布重建技术(Targeted Muscle Reinnervation，TMR)通过对假肢的实时直觉控制提高截肢者的运动 功能。然而对于 TMR 技术是否能减轻幻肢痛、移植神经在肌肉内如何分布等问题，目前知之甚少。本文旨在探讨 TMR 手术对大鼠幻肢痛的影响和术后目标肌肉内神经的再分布情况。我们利用坐骨神经横断组(SNT)作为大鼠的疼痛模型， 将神经近端移植到目标肌肉中作为 TMR 模型，并通过大鼠行为学来评价疼痛程度。实验发现，对照组大鼠不出现自残行 为，而 SNT 组和 TMR 组从手术后第二天开始出现自残行为并逐渐加重，但 TMR 组的自残情况明显轻于 SNT 组。利用 Sihler’s 肌内神经染色法可以在目标肌肉内观察到移植神经末端再生的细小分支。实验结果初步证明 TMR 技术对幻肢痛 有一定的缓解作用，并且术后的神经可以在目标肌肉内重新分支分布。     

海水漏油图像区域面积计算方法研究

研究海水漏油图像区域面积准确计算问题。海水表面的漏油图像区域会受到洋流作用的影响,海水底部运动的方向和速度发生非线性变化,从而使漏油图像区域图像分布均匀性较差。传统的漏油图像区域面积计算是针对均匀的漏油图像区域进行计算的,无法避免洋流作用对漏油图像区域模型中均匀性系数的干扰,造成计算准确率过低。提出基于移动图像区域描述优化算法的海水漏油图像区域面积计算方式。通过运算获取海水漏油图像区域边缘空间位置,计算海水漏油图像区域面积,对面积误差进行补偿处理。实验证明,描述优化算法提高了面积计算的精度,避免了洋流造成区域均匀性较差的缺陷。     

一种人体运动重定向方法*

提出人体下肢向量的概念,通过分析人体运动指出下肢向量能保持运动的主要特征,由此提出基于下肢向量特征不变性的人体运动重定向方法,以此提高运动捕获数据的可重用性。该方法面向人体下肢的运动重定向,能够将运动数据从原始骨骼模型重定向到具有不同骨骼长度比例的目标骨骼模型,同时保持原始运动的主要特征。实验结果表明,该方法具有较好的运动重定向效果和较快的计算效率。     

热约束的BBL布局算法研究

在集成电路芯片的现有精确热模型的基础上,提出一种简化的近似模型,与原模型相比,该近似模型的计算复杂度大大降低,提出了基于该模型的集成电路芯片热分布约束布局优化算法,用该近似模型来计算各热源的温度值和对其他热源的温度贡献值,然后用叠加原理计算出VLS1芯片上各点的温度值,热分布优化算法以芯片的平均温度和芯片面积作为优化目标,用模拟退火方法求解,实验结果表明,在考虑热约束的布局结果中,芯片上各点的温度分布均匀,最热点的温度显著降低,而芯片面积的增加却很少。     

基于外观模型的人体下肢关节点定位方法

近年来,人体下肢关节点定位成为了人体运动跟踪与分析中一个重要研究课题。提出了一种下肢关节点自动定位方法,从无关节标记的人体运动图像序列中定位下肢关节点。该方法首先采用背景剪除技术从图像序列中分割人体目标对象,并建立人体下肢骨架模型。然后,利用关节角度预测方法估计膝踝关节点的位置,在基于下肢外观模型的匹配计算基础上获得下肢关节点的真实位置。实验结果表明,该方法简单有效,下肢关节点定位结果令人满意。     

用于高真实感口型合成的唇区肌肉模型

为了快速合成真实感强的口型,在Waters肌肉模型的基础上,提出了一种新的唇区肌肉模型,弥补了Waters模型对于唇区肌肉的较复杂运动描述不完全的不足。该模型以面部解剖学为基础,通过面部运动的解剖学机理的研究,将唇区的整体运动表示为若干个子运动的线性组合。该模型可用于语音驱动的动画合成。此时,只需在说话人的唇区标定少数几个特征点,就可以获得一组唇区肌肉参数,进而建立相应的肌肉模型。借助于该模型,可以在唇区附近的线性肌的联合作用下,合成说话时的各种口型。实验结果表明,该肌肉模型不仅计算代价小,且合成的口型真实感较强,具有很强的实用性。     

基于人眼多线谱的MPEG-4参数计算

提出了由人眼多线谱计算MPEG-4相关人脸动画参数(FAP)的方法.人眼多线谱利用一组随时间变化的归一化肌肉收缩量表示人眼运动及表情,通过对其采样可获得视频各帧对应的归一化肌肉收量.根据三雏肌肉控制人眼(3D-MCE)模型与MPEG-4标准模型在特征点、运动表示参数,坐标及尺度上的对应关系,可由归一化肌肉收缩量集计算相应FAP,以驱动任意基于MPEG-4标准的人眼模型.实验证明该方法所用数据量及计算量较小,所得MPEG-4参数可以驱动得到较逼真的人眼运动及表情.     

手部运动计算机仿真的实现

根据手部自身的物理特性和生理特性，采用分层技术，严格按照手部解剖学，先建立其骨骼模型，在此基础上形成肌肉模型，最后在肌肉模型上附加一层皮肤。这样，骨骼运动引起肌肉的变形，随着皮肤也跟着发生相应的变化，使虚拟手模型无论从形状上还是运动上都能达到更高程度的逼真效果。     

基于递归神经网络的人体肌肉控制模型研究

在研究了人体运动的基础上提出了一种基于改进的Elman网络模型的人体肌肉动力学模型,给出了网络的学习算法,并以运动员举重提铃动作的下肢肌肉运动为研究对象,建立了最优关节力矩逼近的Elman肌肉动力学网络模型.结果表明该模型通过预测肌肉神经控制激活参数,较好地拟合了关节力矩曲线.     

多目标动态车辆路径问题建模及优化

针对物流配送中动态车辆路径优化问题,综合考虑动态需求、路网影响、车辆共享、时间窗以及客户满意度,建立了多目标动态数学规划模型,该模型能更好地描述现代物流配送问题.同时,提出一种两阶段求解策略,第一阶段采用多目标混合粒子群优化算法获取预优化阶段Pareto最优解,采用改进的粒子状态更新策略并融合模拟退火操作提升粒子群搜索性能,采用自适应网格技术保持解的分布性;第二阶段对客户的需求变化采用贪婪插入和变邻域搜索进行实时路径调整.实验表明,该算法在解空间中有更好的探寻能力,并能快速收敛到全局最优,满足动态路径优化实时性要求.     

Biomimetic Pinching Movements of a Musculo-Skeletal Dual-Finger Model

The present paper investigates pinching movements using an index finger and a thumb actuated by redundant nonlinear digitorum muscles mimicking the configuration of human fingers. A dual-finger model with 2-d.o.f. joints for each finger and redundant nonlinear digitorum muscles is formulated to mimic the structure of human fingers. First, the kinematics and dynamics of the overall finger–object system, as well as the nonlinear muscular dynamics, are derived in accordance with the results of physiological studies. Next, a sensory-motor control law is proposed to enable stable pinching simultaneously with orientation regulation of an object. This control law includes an internal force term generated by co-construction of the redundant muscles. It is shown that the internal force term can modulate the damping factor in the joint space by its nonlinearity. Based on this effect, it is then shown by numerical simulation that our sensory-motor control law with co-contraction of each digitorum muscle makes it possible to realize pinching movements. Therefore, the pinching movements may be realized by means of a musculo-skeletal dual-finger system with the sensory-motor control law and co-contraction of redundant digitorum muscles.     

Influence of selected modeling and computational issues on muscle force estimates

Knowledge of muscle forces and joint reaction forces during human movement can provide insight into the underlying control and tissue loading. Since direct measurement of the internal loads is generally not feasible, non-invasive methods based on musculoskeletal modeling and computer simulations have been extensively developed. By applying observed motion data to the musculoskeletal models, inverse dynamic analysis allow to determine the resultant joint torques, transformed then into estimates of individual muscle forces by means of different optimization procedures. Assessment of the joint reaction forces and other internal loads is further possible. Comparison of the muscle force estimates obtained for different modeling assumptions and parameters in the model can be valuable for the improvement of validity of the model-based estimations. The present study is another contribution to this field. Using a sagittal plane model of an upper limb with a weight carried in hand, and applying the data of recorded flexion and extension movement of the upper limb, the resultant muscular forces are predicted using different modeling assumptions and simulation tools. This study relates to different coordinates (joint and natural coordinates) used to built the mathematical model, muscle path modeling, muscle decomposition (change in number of the modeled muscles), and different optimization methods used to share the joint torques into individual muscles.     

The impact of work configuration,target angle and hand force direction on upper extremity muscle activity during sub-maximal overhead work

Overhead work has established links to upper extremity discomfort and disorders. As many jobs incorporate working overhead, this study aimed to identify working conditions requiring relatively lower muscular shoulder load. Eleven upper extremity muscles were monitored with electromyography during laboratory simulations of overhead work tasks. Tasks were defined with three criteria: work configuration (fixed, stature-specific); target angle (?15°, 0°, 15°, 30° from vertical); direction of applied hand force (pulling backwards, pushing forwards, downwards, sideways, upwards). Normalised electromyographic activity was greater for fixed configurations, particularly when pulling in a backward direction (total activity = 108.3% maximum voluntary exertion (MVE)) compared to pushing down or forward (total activity ranging from 10.5 to 17.3%MVE). Further, pulling backwards at angles of –15° and 0° showed the highest muscular demand (p < 0.05). These results suggest that, if possible, positioning overhead work in front of the body with exertions directed forwards will result in the lowest upper extremity muscle demand.

Statement of Relevance: Overhead work pervades occupational settings and is associated with risk of upper extremity musculoskeletal disorders. The muscular intensity associated with performing overhead work was assessed in several combinations of work placement and hand force direction. These findings should have utility for designing overhead work tasks that reduce muscular exposure.     

A three-dimensional static torso model for the six human lumbar joints

A simple three-dimensional static torso model for the prediction of the force distributions at the six human lumbar levels in different activities was developed. There are two procedures involved in the model calculations, the intersegmental resultant joint forces and moments of the presumed 26 joints and the internal muscoloskeletal force distributions of the 6 intervertebral disc joints. In formulation of the joint force distribution problem, 6 muscle forces and 3 moment equilibrium equations at one of the six disc joints (e.g., L3/L4) with muscle stress (muscle force divided by physiological cross sectional area - PCSA) upper limits were used. The disc compressive force was minimized as the cost function of the linear programming to solve the force distribution problem. This solution of disc force distribution was further substituted into the next level. Such sequential substitutions of joint level's force equilibrium equations were used to solve for the disc forces at all 6 joint levels.     

An imperceptible barcode can reduce the muscle activity required to scan common consumer packaged goods

While the Universal Product Code (UPC) has remained unchanged since its implementation in the 1970s, new technology and consumer package good layouts have started to change the UPC layout. The purpose of this study was to compare how upper extremity muscle activity was altered when scanning consumer packaged goods enhanced with an imperceptible barcode or a multi-sided UPC layout. Seventeen experienced cashiers participated in this study. Electromyography of four bilateral upper extremity muscles was recorded when scanning individual consumer packaged goods and a mock grocery cart. Scanning time and integrated electromyography were compared between the packages enhanced with an imperceptible barcode or the multi-sided barcodes versus the traditional barcodes. Participants were more efficient when scanning packages with the altered barcodes compared to the traditional barcode. Scanning the individual consumer packaged goods resulted in lower peak muscle activity for the shoulder muscles and elbow flexors when using packages enhanced with the imperceptible barcode. When extrapolated over a 4-h shift, the packages enhanced with the imperceptible barcode lowered upper extremity cumulative muscle activity measured muscles; however, the multi-sided layout only demonstrated a reduced muscular activity for the trapezius and left forearm. Future work must continue to assess grocery scanning practices, training, and other alternative scanning practices, such as hand scanners and self-checkout stands.     

THE STATIC MUSCLE LOAD IN DIFFERENT WORK POSITIONS: AN ELECTROMYOGRAPHIC STUDY∗

Abstract

In order to ascertain which muscles and muscle groups are engaged in various standing work positions an electromyographic study was performed.About twenty muscles or muscle groups were examined. Both coaxial needle electrodes and surface electrodes were employed.

The analysis of the muscle activity for different postures was based on action potentials recorded in a normal symmetric standing rest position. Among the different postures the rest position appears to require the least muscular effort for counterbalancing the effect of gravity on the various parts of the body. This state of equilibrium seems to be maintained by certain muscle groups, referred to hero a.s the “ prime postural muscles ”. Only a part of the potential power of the postural muscles is utilized in maintaining the standing symmetric rest position. Some persons engage other muscles besides the prime postural muscles, possibly because they stand in such a way that the load distribution is not optimal, or thoy havo weak prime postural muscles or because of poor muscular co-ordination as a consequence of “ non-physiologic” postural habits.

When changing from the rest position to most of the other standing positions the load on the prime postural muscles is increased, and in many cases other muscle groups arc activated as well. The sacrospiualis appears to be particularly susceptible to change in the load distribution. The muscles of the lower leg, which control the foot articulation, are also very susceptible to changes in body posture. However, a change in the position of the- trunk need not result in an appreciable increase in the load on the muscles of the lower legs if the displacement of the centre of gravity of the trunk is compensated by a postural adjustment at the ankle, such that the point of intersection of tho line of gravity of the body and the supporting area will be the same as in the symmetric standing rest position.

A change in posture of the hip- and knee-joints does not result in such a wide variation in activity of the muscles rogulating the position of these joints as a postural change in the foot articulation and the vertebrae.     

A systems-level perspective of the biomechanics of the trunk flexion-extension movement: Part II – Fatigued low back conditions

Our companion paper demonstrated the importance of a systems-level perspective on spine biomechanics by showing the effects of lower extremity constraints during simple, trunk flexion-extension motions. This paper explores the impact of trunk muscle fatigue and stress-relaxation of lumbar passive tissues on this systems-level response. Twelve participants performed experimental protocols to achieve lumbar passive tissue stress-relaxation fatigue and lumbar muscle fatigue. Participants performed full range of sagittal-plane trunk flexion-extension under unconstrained stoop movement and pelvic/lower extremity constrained stoop movement. They performed these motions both before and after the fatigue protocols and trunk kinematics and muscle activities in trunk and lower extremity muscles were monitored. Under the condition of passive tissue fatigue, low back muscles and lower extremity muscles revealed significantly increased activation level (21% and 22%, respectively) in the free stoop condition but under the restricted stoop condition, there was no significant effect of the protocol. Under the lumbar muscle fatigue condition, a significant antagonistic and lower extremity activation effect (34% increase in abdominal muscles, 16% increase in lower extremity muscles) was observed in the free stooping condition while these variables were not affected by the protocol under the restricted stooping condition.Relevance to industryFatigue of the lumbar musculature and passive tissues is prevalent in jobs requiring full trunk flexion postures. Developing accurate biomechanical models of spinal stress in these full stooping postures can help in the development of appropriate interventions to reduce the prevalence of back injuries in these jobs.     

Modeling and simulation of powered hip orthosis by pneumatic actuators

In this study, a simulation model for a powered hip orthosis (PHO) with air muscles to predict the gait of paraplegics is presented which can be used as a design tool for hip orthoses. Before simulation, mathematical models for a human dummy with an orthosis and a pneumatic muscle actuator were generated. For the air muscle, coefficients required were obtained by static and dynamic experiments of the air muscle and experiments for the valve controlling the air pressure. The computation was conducted on the ADAMS package together with MATLAB. Computer simulation of the flexion of hip joints by the pneumatic muscle results in similar values to those from gait analysis. With the development of a simulation model for a PHO, the gait simulation model using pneumatic muscles can be used to analyze and evaluate the characteristics and efficiency of a PHO by setting the input and boundary conditions.     

Individual muscle contributions to the swing phase of gait: An EMG-based forward dynamics modelling approach

Muscle activation patterns and kinematic conditions at the beginning of the swing phase of gait were used as input to a forward dynamics simulation of the swing leg. A neuromusculoskeletal model was used to account for the non-linearity between muscle excitation and muscle force outputs. Following model tuning a close agreement between simulated and measured swing phase kinematics was obtained. Simulation results suggest that swing leg muscles play an important role in controlling the motion of the swing leg during walking, and that the effect of individual muscles is not necessarily restricted to the joints they span or their basic anatomical classifications.