中国高压电缆运行 情况简要分析

110kV及以上高压电缆在中国大陆地区运行已有40多年的历史,本文简要分析了高压电缆系统在电缆终端、接头、本体、接地系统等方面出现过的主要问题,总结了国内北京、上海、广州等地区在高压电缆运行维护方面的主要经验和先进技术手段。     

多参数监护仪的质量检测和故障分析

多参数监护仪可连续长时间地监测病人的重要生命特征参数,为抢救病人提供第一手临床信息资料和多种生命特征参数,被广泛地应用于各医疗机构中。本文简要介绍了多参数医用监护仪中心电、无创血压和血氧饱和度几个性能参数的测量原理和检测方法,分析了检测过程中常见的故障及处理方法。     

CS-160型高速涡轮牙钻机故障检修一例

针对高速涡轮牙钻机在教学使用中出现的一次压缩机卡缸故障,进行分析和检修,总结设备损坏的原因和设备使用及操作的注意事项。     

Adaptive fault tolerant control design for Takagi–Sugeno fuzzy systems with interval time‐varying delay

This paper deals with the problem of fault‐tolerant control (FTC) of continuous‐time Takagi–Sugeno fuzzy systems with interval time‐varying delay by using adaptive observer. Through constructing an appropriate type of Lyapunov function, a delay‐dependent criterion is established to reduce the conservatism of designing an active FTC (AFTC). In comparison with the existing techniques in the literature, the proposed approach simplifies the design of an AFTC and gives in only one step of the estimate of state vector, the estimate of actuator fault and the controller gains. Some simulation examples are included to demonstrate the effectiveness of the proposed approach. Copyright © 2013 John Wiley & Sons, Ltd.     

PLX7000B型高频移动式C型臂X射线机典型故障维修3例

介绍了PLX7000B型高频移动式C型臂X射线机的结构组成,详细分析了该设备出现的机架不能动作、图像质量出现问题、手动和自动模块功能按键失控3例故障产生的原因并提出了具体的排除方法,为同行排除类似故障提供了参考。最后指出了采用逐步排除和仔细观察相结合的维修方法对于提高维修效率具有重要意义。     

格列本脲改善小鼠局灶性脑缺血再灌注损伤后期的神经运动功能障碍

目的:研究格列本脲对脑缺血再灌注损伤小鼠后期神经运动功能障碍的影响?方法:应用C57BL/6小鼠,制备局灶性脑缺血再灌注损伤模型,经灌胃给予格列本脲(20 mg/kg)连续治疗5周,每周监测小鼠的空腹血糖与体重变化?通过角测试?圆柱体测试?转棒实验及踏空实验等观察小鼠的行为学改变,免疫组织化学染色法观察缺血脑区星形胶质细胞的变化?结果:格列本脲(20 mg/kg)连续治疗5周,不影响小鼠的空腹血糖;与对照组比较,从治疗第2周开始,能显著增加小鼠的体重(P < 0.01);从治疗第3周开始,能减少踏空实验中小鼠的足失误率(P < 0.05)及延长转棒实验中的棒上停留时间(P < 0.05),并减少缺血脑区胶质瘢痕的形成范围(P < 0.05)?结论:格列本脲连续治疗能够促进小鼠脑缺血再灌注损伤后期神经运动功能的恢复?     

气动调节阀黏滞故障引起的回路振荡消除方法

气动调节阀的黏滞故障是控制回路中常见的故障,由黏滞引起的回路振荡将会破坏整个控制回路的性能。针对不具有定位器的阀门,提出了利用T-S型模糊控制器代替传统的PI控制器来消除此种振荡。该控制器利用阀门黏滞时被控对象的状态信息与控制器输出变化率之间的关系来构建模糊控制的规则。通过对传统PI控制器的积分系数进行修正使得阀门快速移出黏滞区,最终消除黏滞故障对回路的影响。将该算法应用于实际的液位控制回路中,实验结果表明该算法能够较好地消除回路的振荡,且能够适应不同的设定值,具有一定的鲁棒性。     

Decoupling between Shockley partials and stacking faults strengthens multiprincipal element alloys

Mechanical properties are fundamental to structural materials, where dislocations play a decisive role in describing their mechanical behavior. Although the high-yield stresses of multiprincipal element alloys (MPEAs) have received extensive attention in the last decade, the relation between their mechanistic origins remains elusive. Our multiscale study of density functional theory, atomistic simulations, and high-resolution microscopy shows that the excellent mechanical properties of MPEAs have diverse origins. The strengthening effects through Shockley partials and stacking faults can be decoupled in MPEAs, breaking the conventional wisdom that low stacking fault energies are coupled with wide partial dislocations. This study clarifies the mechanistic origins for the strengthening effects, laying the foundation for physics-informed predictive models for materials design.

Multiprincipal element alloys (MPEAs) have triggered ever-increasing interest from the physics and materials science community due to their huge unexplored compositional space and superior physical, mechanical, and functional properties (1–12). They also provide an ideal platform to study fundamental physical mechanisms (6, 9, 13, 14). With the rise of MPEAs, understanding their mechanical properties has become a central topic in materials science in the last decade. In face-centered cubic (fcc) MPEAs, the motion of partial dislocations (Shockley partials) and their associated stacking faults (SF) defines their mechanical properties. Alloys with low SF energies (SFEs) have more extended SFs, which are generally believed to have more strength and ductility through twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) mechanisms (15–17).Although extensive endeavors have been made, the commonalities in the origins of high-yield stresses shared by many MPEAs remain elusive. Among the most common intrinsic contributions of yield stresses are the lattice friction (or Peierls stress) and solute solution strengthening (18–22). Since the birth of MPEAs, it has been a controversy about the relative importance of Peierls stress among the other contributions of yield stress, including the solid-solution strengthening effect (18, 21–23). Many researchers assume small Peierls stresses based on the common wisdom of conventional alloys and pure metals (24, 25) and the low SFEs in MPEAs. Low SFEs usually accompany small Peierls stresses. Overall, this controversy originates from the lack of accurate dislocation geometry in MPEAs, which allows for a direct, critical evaluation of the Peierls stress. There are reports on the dislocation geometry in MPEAs, but almost all of them focused on the widths of SFs (26–28). In contrast, the core widths of Shockley partials are rarely reported for MPEAs, partly due to the difficulty in measurements and partly due to unawareness of its importance. To address this issue, we need very accurate determination of the core width of the Shockley partials. It is an important input parameter for mechanical simulations and various theories and models (21, 29–31). Here, we adopt three of the most extensively studied MPEAs, NiCoCr, VCoNi, and CoCrFeNiMn, and their only common fcc element, Ni, to address the above issues.The commonalities in the origins of high-yield stresses shared by the MPEAs can be indicated by the minimum energy profile along the dislocation motion path, i.e., the increased energies introduced by generalized SFEs (GSFEs; Fig. 1A). The local minima of the curves are SFEs, and the maxima are the theoretical energy barriers for pure shearing, which is a good indicator of the changes of Peierls stresses. Assisted by the accurate density functional theory (DFT), we compute GSFE curves for several representative MPEAs and their common fcc component Ni. This identifies a surprising fact: One of the representative MPEAs, NiCoCr, has a decoupled strengthening effect, i.e., it has a narrower dislocation core of Shockley partial than pure Ni, although its SF is much wider than Ni. Usually, in fcc alloys, when SFE is lower, its unstable SFE (USFE) (maximal GSFE) is also lower, which is coupled. Examples include the two other MPEAs, VCoNi and CoCrFeNiMn, and many Mg alloys (basal plane dislocations) (25) and Al alloys (32). However, NiCoCr does not follow this convention. The understanding from multiscale simulations, atomistic simulations, and the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images rationalizes the narrow core of Shockley partials. These results clearly reveal the diverse and decoupled mechanistic origins for the strengthening effects in the MPEAs with excellent mechanical properties.Open in a separate windowFig. 1.GSFEs of three representative MPEAs and pure Ni. (A) The schematic for the generation of GSFs along the slip direction. The displacement 0.75 is equivalent to –0.25 due to the adopted periodic boundary condition. (B) The atom models at two representative displacements for GSFs. (C) The dashed lines are the fitting of the data points to equation γ=γ0sin 2(πx)+(γu−γ0/2)sin 2(2πx) (64, 65). (D) The GSFEs in C are along the path indicated by the white arrows on the gamma surface, i.e., the minimum energy projected along the path denoted by the orange arrow. The GSFE curves reveal the origin for the wide SF and smaller half-width of Shockley partial of NiCoCr than Ni. We need to decrease SFE, while increasing γ_u, in order to optimize the mechanical properties.     

Nonfragile reliable control for positive switched systems with actuator faults and saturation

This paper presents a nonfragile reliable control approach to positive switched systems with actuator faults and saturation. In order to guarantee the reliability of the controller, the controller gain matrix is chosen as the sum of a normal gain matrix and a gain perturbation matrix. A nonfragile reliable control is first proposed for the considered systems using a gain matrix decomposition technique. Then, the presented nonfragile control design approach is developed for the systems with exogenous disturbances. An approach to compute the normal gain matrix and the gain perturbation matrix is also provided. Under the obtained controller, the resulting closed‐loop systems are positive and L₁‐gain stable. Meanwhile, all the states will stay inside a cone. All presented conditions are described via linear programming. Finally, two examples are provided to verify the effectiveness of the theory findings.     

Observer‐based actuator fault estimation and proportional derivative fault tolerant control for continuous‐time singular systems

This paper focuses on designing fault estimation (FE) and fault tolerant control (FTC) schemes for continuous‐time singular systems affected by actuator fault. A novel observer called the extended proportional integral observer (PIO) is designed so that the estimations of system state and actuator fault can be obtained simultaneously. In contrast with the traditional PIO, better estimation performance can be obtained by using the designed observer. Furthermore, with the obtained FE information, a novel proportional derivative–type FTC scheme is given by means of the separation property and the free‐weighting matrix technique, which ensures that the closed‐loop system is normal and stable. All the feasible conditions are formulated in linear matrix inequality (LMI) frameworks. Finally, two examples are simulated to prove the superiority and practicability of the presented scheme.