Robust state estimation based on sliding mode observer for aeroelastic system

This paper concerns the application and demonstration of sliding mode observer for aeroelastic system, which is robust to model uncertainty including mass and stiffness of the system and various disturbances The performance of a sliding mode observer is compared with that of a conventional Kalman filter to demonstrate robustness and disturbance decoupling characteristics. Aeroelastic instability may occur when an elastic structure is moving even in subcritical flow speed region Simulation results using sliding mode observer are presented to control aeroelastic response of flapped wing system due to various external excitations as well as model uncertainty and sinusoidal disturbances in subcritical incompressible flow     

局部故障间隔模型与维修周期的单样本估算

在研究可修系统局部故障率模型的基础上，以局部故障时间间隔为对象，建立一种可修系统状态分析的新模型。根据新模型进行参数估计，可以有效地预测系统的维修周期。新方法特别适用于大型复杂的单样本可修系统，文中介绍了相应的应用实例。     

直流偏磁条件下变压器励磁电流及铁心损耗计算

提出了一种综合考虑变压器非线性影响的计算直流偏磁条件下变压器励磁电流及铁心损耗的解析方法,给出了变压器非线性模型的具体建模过程,并通过有限元分析及试验结果验证了仿真的正确性。     

基于绕组变形测量的电力变压器剩磁大小估算

本文中作者通过理论和试验研究分析了变压器剩磁对变压器绕组变形测量结果的影响,提出了一种电力变压器剩磁大小估算方法。     

负偏压形核法增强金刚石薄膜附着力研究

在微波等离子体化学气相沉积装置中 ,研究了负偏压形核对金刚石薄膜与WC 6 %硬质合金刀具附着力的影响。结果表明 ,负偏压形核不仅能增加金刚石的核密度 ,还能改善金刚石核在WC晶粒上分布的均匀性 ,增加膜基有效结合面积 ,从而增加金刚石薄膜附着力。因负偏压形核时含碳离子被偏压电场加速 ,对刀具表面产生溅射作用 ,采用铜替代置换钴的刀具 ,使用负偏压形核反而降低薄膜附着力 ;而采用磁控溅射镀铜的刀具 ,使用负偏压形核则能进一步提高金刚石薄膜的附着力。     

居住区绿地的美景度评价

美景度评价是景观评价最有效的方法之一,应用此方法分析居民对居住区绿地的景观偏好对今后的居住区绿地设计有重要的指导意义.评价结果表明,不同背景的5个测试群体在居住区绿地审美方面存在普遍一致性,2个具有专业背景的群体的相关性较其他各种类型的人之间的相关性更好.在诸多影响因子中,水体,尤其是具有动势的水景形式是一个影响美景度评价的重要因子;冠幅是影响美景度评价的又一重要因子.     

Exchange bias and magneto-resistance in an all-oxide spin valve with multi-ferroic BiFeO3 as the pinning layer

Modern microscopy techniques indicate that the electrical switching of magnetic domains in multi-ferroic materials is possible. However, the application of such functionality in a real device has yet to be proven. In this work we fabricated an all-oxide spin valve with the ferroelectric anti-ferromagnet BiFeO₃ (BFO) as the pinning layer. The multi-layered heterostructure was grown epitaxially on a (0 0 1) SrTiO₃ substrate and magneto-resistance was achieved at room temperature, which was switchable magnetically in a similar way to conventional metallic spin valves. Some key physical and material issues for building up such a novel device were addressed, in particular the hetero-epitaxy-induced strain effects on the electrical and magnetic properties of each layer and the establishment of exchange bias between BFO and an oxide ferrimagnet, e.g. Zn_0.7Ni_0.3Fe₂O₄ (ZNFO). The strains caused a significant increase in the coercivity but a decrease in the saturation magnetization of the ferrimagnet used. The former is particularly undesirable because it increases the required switching field. The all-oxide architecture allowed the spin valve to be field annealed from a temperature above the high Néel point of BFO (～660 K), after which a very large exchange bias field (H_ex) was achieved at 5 K and kept at a decent value at room temperature. The H_ex–T curve did not follow the widely observed (1 ? T/T_N)^β temperature dependence, but could be explained by the random field model with one-dimensional (1-D) anti-ferromagnetic sublattice magnetization derived from the spin wave theory. Based on the observed 1-D spin wave behavior and the geometric arrangements of the paramagnetic ions at the (0 0 1) surface we propose an atomic model in which only a part of the spin along the diagonal lines in the BFO (0 0 1) surface was strongly exchange coupled with ZNFO.     

Analysis of disclosure avoidance procedures

In the collection of data on environmental health, individuals are frequently reluctant to be entirely candid with surveyors because of concern over the confidentiality of responses. A standard procedure is to inoculate the response with random modification (or error) so that it becomes impossible to identify individual respondents but quite possible to generate unbiased statistical summaries of the entire sample. This paper is directed at generating methods for such random inoculation and abstracting from the inoculated results those conclusions concerning sample response and population estimates. A numerical example of a bivariate randomized procedure is given.     

Analysis and design of second-order sliding-mode algorithms for quadrotor roll and pitch estimation

The problem addressed in this paper is that of quadrotor roll and pitch estimation without any assumption about the knowledge of perturbation bounds when Inertial Measurement Units (IMU) data or position measurements are available. A Smooth Sliding Mode (SSM) algorithm is first designed to provide reliable estimation under a smooth disturbance assumption. This assumption is next relaxed with the second proposed Adaptive Sliding Mode (ASM) algorithm that deals with disturbances of unknown bounds. In addition, the analysis of the observers are extended to the case where measurements are corrupted by bias and noise. The gains of the proposed algorithms were deduced from the Lyapunov function. Furthermore, some useful guidelines are provided for the selection of the observer turning parameters. The performance of these two approaches is evaluated using a nonlinear simulation model and considering either accelerometer or position measurements. The simulation results demonstrate the benefits of the proposed solutions.     

Health body priming and food choice: An eye tracking study

The “gaze bias theory” suggests that people tend to look longer at items that are eventually chosen. This was not entirely confirmed for food choice, a complex phenomenon influenced by many factors. Although it has been shown that health-related primes affect both consumer attention and choice, the effect of unhealthy body shape primes on these outcomes is largely unknown. Therefore, we here investigated how body primes, namely normal weight (NW), severely overweight (OW) and severely underweight (UW) body shapes, influenced attention and choice for low-calorie food (LcFd) and high-calorie food (HcFd). We hypothesized that OW and UW primes would activate opposing health goals (weight-loss vs. weight-gain respectively). Fifty normal weight sated females completed a primed food choice task in which choices between a LcFd and HcFd, matched for subjective liking, were presented after control or human body shapes (NW, UW or OW). In each trial participants had to identify the shape (i.e., non-human, human male or human female) and then choose the food they wanted to eat at that moment. Gaze was recorded by an eye tracker. Results showed that, although primes did not influence the choice, the total dwell time on chosen HcFd was higher when preceded by an OW prime compared with chosen LcFd and chosen HcFd preceded by an UW prime. Also, both total dwell time and the number of fixations were higher for chosen food compared with non-chosen food as well as for HcFd compared with LcFd without a corresponding higher proportion of HcFd choice. Overall, these data shed light on the interactions between attention, health body priming and food choice.