Surface morphology and nodule formation mechanism of cellulose acetate membranes by atomic force microscopy

By the use of atomic force microscopy (AFM), formation mechanism of nodular structure in cellulose acetate membranes was systematically investigated. Elementary factors affecting the nodule formation were delineated on the basis of both kinetic and thermodynamic considerations. It was shown that (1) the exact nature of nodular structure is thermodynamic equilibrium glassy state; nodular structure will vanish in the rubbery state; (2) the thermodynamic factor affecting nodule formation is the membrane formation temperature; with the membrane formation temperature decreasing, more chain segments are able to form nodular structures; (3) nodule formation is dependent on the segment rearrangement; variation of the solvent environment is the major kinetic factor affecting the segment rearrangement and nodule formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1328–1335, 2003     

A low-cost real time virtual system for postural stability assessment at home

Background and objective

The degeneration of the balance control system in the elderly and in many pathologies requires measuring the equilibrium conditions very often. In clinical practice, equilibrium control is commonly evaluated by using a force platform (stabilometric platform) in a clinical environment.In this paper, we demonstrate how a simple movement analysis system, based on a 3D video camera and a 3D real time model reconstruction of the human body, can be used to collect information usually recorded by a physical stabilometric platform.

Methods

The algorithm used to reconstruct the human body model as a set of spheres is described and discussed. Moreover, experimental measurements and comparisons with data collected by a physical stabilometric platform are also reported. The measurements were collected on a set of 6 healthy subjects to whom a change in equilibrium condition was stimulated by performing an equilibrium task.

Results

The experimental results showed that more than 95% of data collected by the proposed method were not significantly different from those collected by the classic platform, thus confirming the usefulness of the proposed system.

Conclusions

The proposed virtual balance assessment system can be implemented at low cost (about 500$) and, for this reason, can be considered a home use medical device. On the contrary, astabilometric platform has a cost of about 10,000$ and requires periodical calibration. The proposed system does not require periodical calibration, as is necessary for stabilometric force platforms, and it is easy to use. In future, the proposed system with little integration can be used, besides being an emulator of a stabilometric platform, also to recognize and track, in real time, head, legs, arms and trunk, that is to collect information actually obtained by sophisticated optoelectronic systems.     

Design of a slave arm of a surgical robot system to estimate the contact force at the tip of the employed instruments

Acquisition of the contact force at the instrument tip can enable better performance, e.g. transparency of the haptic feedback in the surgical robot systems. It is, however, difficult to measure the contact force directly due to technical limitations in attaching sensors to the tip of the instruments. This paper proposes a method to estimate the forces by installing the sensors away from the instrument tip. The proposed method employs specially designed mechanical parts of the slave robot, i.e. a slider cover plate for the z-axis translational force along the insertion direction, and docking clamps for the rotational pivot torques around the fulcrum point. Strain gauges are attached to specially designed places with enhancing shapes. The simulation results of the force estimation are presented to confirm the strain concentration area. The proposed method is validated with quantitative experimental results. Calibrated weights are determined upon the comparison of the strain value with a calibrated 6-axis force/torque sensor. The percentage error in the force calibration is about 5~8% calculated by the root mean square error (RMSE) of force-sensing performance. In addition, it can be computed by considering only the bending phase of each sensor although the hysteresis is observed from the calibration graph.     

Tactile display with tangential and normal skin displacement for robot-assisted surgery

This paper proposes a tactile display providing both shear and normal feedback to the fingertip for generating three-axis tactile feedback during teleoperation of a surgical robot. The display is composed of five balloons actuated by controlling the pneumatic pressure. The implemented display is 18?mm?×?18?mm?×?15?mm. This size is suitable for mounting the display onto the master controls of a surgical robot. The maximum normal and shear displacements are 2 and 1.3?mm, respectively. The proposed tactile display may provide perceivable stimuli to a human finger pad in all five directions: normal, distal, proximal, radial, and ulnar. This paper also reports on the results of psychophysical measurement of the minimum perceivable movement of the developed tactile display for each of the five directions.     

基于AD7884的分离脱落电连接器机械分离力测试台的设计

基于分级型模数转换器AD7884对分离脱落电连接器的分离力进行测量,采用8位单片机W77E58与之接口,进行数据处理并通过485串口传输到上位机。实现了对分离脱落电连接器的分离力进行测量,系统运行稳定,且与上位机数据交互简单、可靠。     

浅析SRT-Ⅳ裂解炉炉管弯曲及断裂原因

主要分析计算了裂解炉炉管受力情况，进而得出结论：裂解炉自身结构的相互约束力和炉管渗碳是导致炉管弯曲、断裂的主要原因，并提出了相应的解决措施。     

六维腕力传感器非线性正解耦方法设计

多维力传感器利用其多个转换单元完成测量加载于其结构上未知负载的作用效果,解耦是其设计的重要组成部分。针对传统静态线性解耦方法的不足,试图将传统线性解耦方程扩展为多项式结构,受其多元高次方式通解形式的启发,构造了一种多项式非线性静态正解耦方程,该方法无需传统线性解耦方法中的曲线拟合、逆解,不依赖以系统是线性为前提,且方程可以扩展成任意结构的多项式。实验结果表明:该方法能降低输出耦合误差。     

Hydrodynamic drag forces on two porous spheres moving along their centerline

This paper numerically evaluates the hydrodynamic drag force exerted on two highly porous spheres moving steadily along their centerline (sphere #1 and sphere #2) through a quiescent Newtonian fluid over a Reynolds number ranging from 0.1 to 40. At creeping flow limit, the drag forces exerted on both spheres were identical. At higher Reynolds numbers the drag force on sphere #1 was higher than sphere #2, revealing the shading effects produced by sphere #1 on sphere #2. At dimensionless diameter (β, =d_f/2k^0.5, d_f and k are floc diameter and interior permeability, respectively) >20, the spheres can be regarded nonporous. At β<20, the drag forces dropped. At β<2, the drag forces approached “no-spheres” limit. An increased size ratio of two spheres (d_f1/d_f2) would increase the drag force on sphere #1 and reduce that on sphere #2. At increasing β for both spheres, the drag force on sphere #2 was increased because of the more difficult advective flow through its interior, and at the same time the drag was reduced owing to the stronger wake flow produced by the denser sphere #1. The competition between these two effects leads to complicated dependence of drag force on sphere #2 on β value. These effects were minimal when β became low. Two identical spheres could move steadily along their centerline. At higher Reynolds number, the two spheres would move closer because of the incorporation of inertia force. For spheres of different diameters, the sphere # 2 would move faster than sphere #1 regardless of their size ratio and β value. This occurrence yielded efficient coagulation when two porous spheres were moving in-line.     

电动汽车机电复合制动力分配策略研究

为了实现再生制动力与机械制动力在驱动轮和从动轮之间的优化分配,在保证车辆制动安全的同时提高能量回收效率,将汽车理想制动力分配I曲线与模糊算法相结合,提出一种基于模糊控制的电动汽车机电复合制动力分配策略。设计了电动汽车再生制动力分配模糊控制器,根据车辆工况与理想制动力分配I曲线,计算前后轮上分别应加载的机电复合制动力大小。建立了电动汽车制动系统动力学仿真模型,在此基础上进行仿真分析。最后利用Advisor仿真软件对该分配策略进行回收能量效率测试。结果表明,该分配策略既能保证汽车前后轮的制动力分配按照理想制动力I曲线分布,确保汽车的制动安全;又能有效地实现再生制动能量回收,提高电动汽车的续驶里程。     

容器设计中搅拌装置的轴向力分析

搅拌装置在化工厂中应用很广，在磷肥、钛白粉装置中（15kt/a)使用较多，仅钛白粉装置中就大约有40－50台，如增稠结晶器，中和槽等，搅拌操作所涉及的因素极为复杂，浆叶形式的选择，从力学的观点来说，迄今研究不够，本文就搅拌装置产生的轴向力问题进行了初步研究。