Adaptive Fuzzy PD+ Control for Attitude Maneuver of Rigid Spacecraft

In this paper, an adaptive fuzzy PD+ controller is proposed for the attitude maneuver of rigid spacecraft. The novel controller adjusts the gains of the PD+ attitude controller online according to attitude errors and angular velocity errors during the maneuver procedure. Therefore, quick response and avoidance of actuator saturation can be achieved simultaneously. Furthermore, the adaptation mechanism is designed, based on Lyapunov theory, to guarantee the stability of the closed‐loop system. To achieve good performance of the closed‐loop system under the constraint of actuator saturation, controller parameter optimization is developed on the basis of a genetic algorithm. Simulation results show that the transient performance and robustness against parametric uncertainty and environmental disturbance of the adaptive fuzzy PD+ controller are better than those of a constant PD+ controller.     

Particle swarm algorithm with adaptive constraint handling and integrated surrogate model for the management of petroleum fields

This paper deals with the development of effective techniques to automatically obtain the optimum management of petroleum fields aiming to increase the oil production during a given concession period of exploration. The optimization formulations of such a problem turn out to be highly multimodal, and may involve constraints. In this paper, we develop a robust particle swarm algorithm coupled with a novel adaptive constraint-handling technique to search for the global optimum of these formulations. However, this is a population-based method, which therefore requires a high number of evaluations of an objective function. Since the performance evaluation of a given management scheme requires a computationally expensive high-fidelity simulation, it is not practicable to use it directly to guide the search. In order to overcome this drawback, a Kriging surrogate model is used, which is trained offline via evaluations of a High-Fidelity simulator on a number of sample points. The optimizer then seeks the optimum of the surrogate model.     

基于改进粒子群优化算法的火电厂机组负荷分配

以坑口电厂厂级监控信息系统的机组负荷在线优化分配功能模块为应用背景,针对模块所运用的基本粒子群优化算法在优化过程中容易陷入局部收敛、收敛速度慢的缺点,提出一种基于惯性权重非线性减小策略的改进粒子群优化算法,使惯性权重呈对数减小;测试函数仿真结果表明,改进粒子群优化算法在收敛速度和寻优精度方面,优化性能均优于基本粒子群优化算法;通过MATLAB与Visual C++混合编程,开发了机组负荷在线优化分配功能模块,提高了算法的计算效率和工程应用价值。     

Segmentation of the left ventricle in cardiac cine MRI using a shape-constrained snake model

Segmentation of the left ventricle (LV) is a hot topic in cardiac magnetic resonance (MR) images analysis. In this paper, we present an automatic LV myocardial boundary segmentation method using the parametric active contour model (or snake model). By convolving the gradient map of an image, a fast external force named gradient vector convolution (GVC) is presented for the snake model. A circle-based energy is incorporated into the GVC snake model to extract the endocardium. With this prior constraint, the snake contour can conquer the unexpected local minimum stemming from artifacts and papillary muscle, etc. After the endocardium is detected, the original edge map around and within the endocardium is directly set to zero. This modified edge map is used to generate a new GVC force filed, which automatically pushes the snake contour directly to the epicardium by employing the endocardium result as initialization. Meanwhile, a novel shape-similarity based energy is proposed to prevent the snake contour from being strapped in faulty edges and to preserve weak boundaries. Both qualitative and quantitative evaluations on our dataset and the publicly available database (e.g. MICCAI 2009) demonstrate the good performance of our algorithm.     

Particle filters and occlusion handling for rigid 2D–3D pose tracking

In this paper, we address the problem of 2D–3D pose estimation. Specifically, we propose an approach to jointly track a rigid object in a 2D image sequence and to estimate its pose (position and orientation) in 3D space. We revisit a joint 2D segmentation/3D pose estimation technique, and then extend the framework by incorporating a particle filter to robustly track the object in a challenging environment, and by developing an occlusion detection and handling scheme to continuously track the object in the presence of occlusions. In particular, we focus on partial occlusions that prevent the tracker from extracting an exact region properties of the object, which plays a pivotal role for region-based tracking methods in maintaining the track. To this end, a dynamical choice of how to invoke the objective functional is performed online based on the degree of dependencies between predictions and measurements of the system in accordance with the degree of occlusion and the variation of the object’s pose. This scheme provides the robustness to deal with occlusions of an obstacle with different statistical properties from that of the object of interest. Experimental results demonstrate the practical applicability and robustness of the proposed method in several challenging scenarios.     

溪洛渡水电站掺PVA纤维混凝土的试验研究及应用

溪洛渡水电站拦河大坝为双曲拱坝,最大坝高285．5m,大坝混凝土抗裂指标要求高,为了提高混凝土的极限拉伸值、自生体积变形性能,进行外掺改性PVA纤维大坝混凝土配合比的试验研究,并在溪洛渡水电站工程成功应用。室内试验研究和对大坝混凝土的抽样检测结果表明,掺改性PVA纤维混凝土可提高28d龄期混凝土极限拉伸值10％以上,相同龄期可减少混凝土自生体积变形收缩约15×10^-6左右,有效的提高了大坝混凝土的抗裂性能指标。     

石拱桥拱圈加固的约束机理分析

通过分析套箍和砌体横向应变关系,探讨了采用钢筋昆凝土套箍加固石拱桥对核心砌体的约束机理,并提出了套箍对核心砌体的约束应力及由于套箍约束作用使砌体强度提高的计算方法.同时,通过此方法对巴中市南江县龙渠大桥进行了加固设计,计算后得知主拱圈承载力得到明显提高,且实际运用效果良好.     

公路工程造价风险规避策略

目前,造价风险管理人员一般是根据项目的具体情况,对不同的风险采用不同的处置方法。公路工程也一样,文章就两大处置策略对公路工程造价风险进行规避,力争将损失降低到最低程度。     

并行部署的改进型SSL工控VPN模型

工控网络中的通信实时性非常重要,但普通SSLVPN一直不能很好的满足其实时性需求,为此这里提出了一套改进SSL协议的措施,并依据这些措施构建了一个并行部署2台SSLVPN的新模型,分析了改进SSL协议的各个措施。通过引用基础数据计算出了模型改进前后的系统耗时,由此得出了新模型的实时性改善度为1．5,时间节省率为33％;最后补充介绍了该模型有待进一步研究的一些技术课题,展望了其应用前景。     

改进的遗传算法应用于碎片拼接

碎片拼接实际用途已经越来越广泛,本文讲述传统碎片拼接的方法,引出图形匹配策略,传统的碎片拼接算法大多需要大量繁琐的计算,大大增加了算法的时间复杂度,依据传统算法的不足,改进遗传算法应用于碎片匹配策略,提出可以实现更高效率、更高准确率的碎片拼接算法。