静电电动机实验研究

对两电极间电荷移动过程中电极间空气所受的影响以及转子转动进行了实验研究,建立了离子流、空气涡流的模型,并探索了静电电动机的工作机理.实验及理论分析表明,引起转子转动的原因是空气涡流产生的效应.     

超声旋转行波马达研究

采用解析法求解了环形行波超声马达定子振动的幅频特性，并在此基础上，依据马达转子的动力学方程，建立了定子与转子间的接触数学模型，从理论和实验两个方面分析了输入激励电源频率及电压大小变化对马达输出机械特性的影响，结果表明，超声马达的输出特性与激励电源的参数密切相关，在谐振频率附近，马达的阻转力矩和输出转速都有较大增加，增加驱动电压，阻转力矩和输出转速将单调增大。     

Sub-piconewton force fluctuations of actomyosin in vitro.

A new system has been developed for measuring the forces produced by a small number (less than 5-150) of myosin molecules interacting with a single actin filament in vitro. The technique can resolve forces of less than a piconewton and has a time resolution in the submillisecond range. It can thus detect fluctuations of force caused by individual molecular interactions. From analysis of these force fluctuations, the coupling between the enzymatic ATPase activity of actomyosin and the resulting mechanical impulses can be elucidated.     

关于一种电机交流电源的改进性设计

作为精密敏感元件电机的供电电源,在工程实践中,对电机交流电源的设计要求严格。针对一种精密敏感元件电机的交流电源进行改进设计和分析研究,找出了该交流电源电路+24 V和交流输出下拉的设计缺陷,提出了采用能防止两场效应管同时导通的驱动电路的设计方案和解决措施,并通过了试验验证。     

Planar polarized actomyosin contractile flows control epithelial junction remodelling

Force generation by Myosin-II motors on actin filaments drives cell and tissue morphogenesis. In epithelia, contractile forces are resisted at apical junctions by adhesive forces dependent on E-cadherin, which also transmits tension. During Drosophila embryonic germband extension, tissue elongation is driven by cell intercalation, which requires an irreversible and planar polarized remodelling of epithelial cell junctions. We investigate how cell deformations emerge from the interplay between force generation and cortical force transmission during this remodelling in Drosophila melanogaster. The shrinkage of dorsal-ventral-oriented ('vertical') junctions during this process is known to require planar polarized junctional contractility by Myosin II (refs 4, 5, 7, 12). Here we show that this shrinkage is not produced by junctional Myosin II itself, but by the polarized flow of medial actomyosin pulses towards 'vertical' junctions. This anisotropic flow is oriented by the planar polarized distribution of E-cadherin complexes, in that medial Myosin II flows towards 'vertical' junctions, which have relatively less E-cadherin than transverse junctions. Our evidence suggests that the medial flow pattern reflects equilibrium properties of force transmission and coupling to E-cadherin by α-Catenin. Thus, epithelial morphogenesis is not properly reflected by Myosin II steady state distribution but by polarized contractile actomyosin flows that emerge from interactions between E-cadherin and actomyosin networks.     

Stimulation of Acanthamoeba actomyosin ATPase activity by myosin-II polymerization

Phosphorylation of the regulatory light chains of vertebrate smooth muscle or cytoplasmic myosins alters the structure of myosin monomers, favours myosin filament formation and stimulates the actin-activated Mg2+-ATPase of myosin. Similarly, in Dictyostelium and Acanthamoeba phosphorylation of the myosin heavy chains exhibits both polymerization and actin-activated Mg2+ATPase. Unfortunately, the relationships between phosphorylation, myosin assembly and activation of ATP hydrolysis are not fully understood in any of these systems, as there has been no way of varying the extent of polymerization of intact myosin without changing solution conditions or the level of myosin phosphorylation, parameters that may have independent effects on ATPase activity. Taking an entirely new approach, we have used monoclonal antibodies against the tail of Acanthamoeba myosin-II that cause filament disassembly to show that myosin polymerization itself stimulates actomyosin ATPase activity. With a fixed level of myosin-II phosphorylation and constant solution conditions, depolymerization of myosin-II filaments by antibodies causes a concomitant loss of actin-activated ATPase activity.     

电力测功电机影响因素分析

讨论了变频电源输入电压的非正弦对测功电机的性能影响，提出了改善不利影响的措施。     

基于交叉口处机动车交通行为概率的延误模型

通过分析信号控制交叉口处机动车的交通行为,利用交叉口的信号周期、有效绿灯时间,求得各种交通行为的概率和平均延误时间,提出一种基于分析各种交通行为概率的交通延误的模型。以石家庄市中山东路与建设南大街交叉口为例,采用Beckham模型对其进行交通流延误的计算。经过对结果的对比,误差为2%,在规定的误差范围内,说明基于分析交通行为概率的延误模型可以为计算交叉口处车辆的平均延误提供一种估计方法,并且求得的平均延误也可以作为评价交叉口服务水平的指标之一。     

高压电动机故障诊断人工神经网络法

分析了高压电动机的故障特征,对高压电动机故障诊断人工神经网络法进行了讨论.并应用对称分量法理论,提出基于正序、负序、零序电流分量的高压电动机故障诊断人工神经网络法.建立了一个5层前向神经网络,对采用了有效的网络学习算法进行了讨论,为全面、快速和准确地实现高压电动机故障诊断,以提高其运行的安全性和可靠性提供了依据.     

Polar actomyosin contractility destabilizes the position of the cytokinetic furrow

Cytokinesis, the physical separation of daughter cells at the end of mitosis, requires precise regulation of the mechanical properties of the cell periphery. Although studies of cytokinetic mechanics mostly focus on the equatorial constriction ring, a contractile actomyosin cortex is also present at the poles of dividing cells. Whether polar forces influence cytokinetic cell shape and furrow positioning remains an open question. Here we demonstrate that the polar cortex makes cytokinesis inherently unstable. We show that limited asymmetric polar contractions occur during cytokinesis, and that perturbing the polar cortex leads to cell shape oscillations, resulting in furrow displacement and aneuploidy. A theoretical model based on a competition between cortex turnover and contraction dynamics accurately accounts for the oscillations. We further propose that membrane blebs, which commonly form at the poles of dividing cells and whose role in cytokinesis has long been enigmatic, stabilize cell shape by acting as valves releasing cortical contractility. Our findings reveal an inherent instability in the shape of the dividing cell and unveil a novel, spindle-independent mechanism ensuring the stability of cleavage furrow positioning.     

Hydrostatic pressure and the actomyosin cortex drive mitotic cell rounding

During mitosis, adherent animal cells undergo a drastic shape change, from essentially flat to round. Mitotic cell rounding is thought to facilitate organization within the mitotic cell and be necessary for the geometric requirements of division. However, the forces that drive this shape change remain poorly understood in the presence of external impediments, such as a tissue environment. Here we use cantilevers to track cell rounding force and volume. We show that cells have an outward rounding force, which increases as cells enter mitosis. We find that this mitotic rounding force depends both on the actomyosin cytoskeleton and the cells' ability to regulate osmolarity. The rounding force itself is generated by an osmotic pressure. However, the actomyosin cortex is required to maintain this rounding force against external impediments. Instantaneous disruption of the actomyosin cortex leads to volume increase, and stimulation of actomyosin contraction leads to volume decrease. These results show that in cells, osmotic pressure is balanced by inwardly directed actomyosin cortex contraction. Thus, by locally modulating actomyosin-cortex-dependent surface tension and globally regulating osmotic pressure, cells can control their volume, shape and mechanical properties.     

一种改进的永磁同步电机直接转矩控制方法

针对传统的永磁同步电机直接转矩控制在低速运行时磁链和转矩脉动大,以及低速时定子电阻的变化导致磁链估算产生较大误差等影响电机稳定运行的问题,提出了一种改进的永磁同步电机直接转矩控制方法。该方法首先利用饱和函数-sat函数代替二阶滑模算法中的符号函数,实现滑模控制切换的连续性,削弱滑模控制中的抖振;然后再利用改进的二阶滑模算法来设计速度和磁链控制器,替代传统的直接转矩中的滞环比较器,抑制转矩和转速的波动;最后通过在磁链估算中建立基于模糊比例积分（proportional integral,PI）控制的定子电阻补偿器,消除定子电阻变化对磁链估算的影响。仿真结果证明了所提方法的有效性与可行性。     

Limitations in the use of actomyosin threads as model contractile systems

Recent studies have suggested that actomyosin threads may provide a useful model for studying the properties of contractile systems. The development of highly sensitive positional feedback transducers has enabled the properties of these threads to be measured reproducibly. Potential applications include such systems as ventricle, smooth muscle and non-muscle preparations, from which it is difficult to obtain suitable fibres for mechanical studies. In addition, studies with chemically modified myosins may provide new insights into the relationships between the biochemical and mechanical events in the cross-bridge cycle. However, there are indications that the mechanical properties of actomyosin threads differ from those of intact fibres in several important respects. For example, contraction velocity is proportional to isometric tension in threads, but is independent of filament density in intact fibres. We have now determined the force-velocity characteristics of actomyosin threads prepared from muscles with known differences in their physiological contraction velocities. No direct relationships could be found between the velocity characteristics of the threads and those of intact muscle. We conclude that the measured velocities of threads reflect properties of the actomyosins other than cross-bridge cycling times, thus severely limiting the usefulness of this technique for comparative purposes.     

中学生体育学习中归因训练的实验研究

探索性地将归因训练引入到体育领域中,通过教学实验来考察中学生体育学习中开展归因训练的可行性和有效性.对归因训练理论中几个争议问题做了部分的解决,并对Weiner的归因效果论进行了检验.研究结论:通过归因训练能够使参加体育课学习的中学生其成败归因?情感?期望水平和意向等向积极方向转化,继而提高学生的坚持性?成就动机和体育学习成绩.多种归因训练方法的综合促使高中生理想归因及其效果的形成;归因训练后的情感?期望?意向等部分出现了积极变化,但与归因维度的联系较为松散.     

基于等效磁路法的平动式啮合电动机静态转矩求解

阐述了平动式啮合电动机的结构和工作原理并采用等效磁路法建立了平动式啮合电动机的准线性分析模型。通过分析电机二维磁场分布和考虑电机特殊的电磁结构,提出了用三种磁通管单元来近似磁场分布,并借用磁力线和等磁位线互换的方法,将磁力线分布不均匀的磁通管引入到分析模型中,有效的处理了平动式啮合电动机中的磁场分布不均匀和磁路局部饱和,使分析模型得到简化并兼顾了求解精度。其静态转矩计算结果与有限元结果相吻合,验证了分析模型的合理性和准确性,表明该模型可以作为平动式啮合电动机结构优化设计的有效分析手段。