Direct Ink-Jet Printing of Vertical Walls

Direct jet printing can assemble ceramic powder into a three dimensional shape by firing droplets of ink through a nozzle to build a multiple layered structure. As with stereolithography and selective laser sintering, the surface texture is expected to witness the layered assembly. The ability to create vertical walls by direct ink-jet printing was explored using a test piece based on a maze. The structure and topography are discussed in terms of droplet spreading and drying.     

基于可变影响空间的多目标进化算法的解集均匀性评价方法

解集的均匀性评价是多目标进化算法中性能评价的要素之一.文中结合面向个体和面向空间的思想,提出可变影响空间的概念,并基于此提出一种解集均匀性评价方法——基于可变影响空间的多目标进化算法的解集均匀性评价方法(VISUM).该方法通过分析个体在可变影响空间内的相对均匀程度,能准确反映解集的分布均匀性.实验结果证明文中方法的可行性和有效性.     

基于二维混合模型和状态观测器的重复控制设计

针对一类正则线性系统, 提出一种基于状态观测器和二维混合模型的重复控制系统设计方法. 首先, 通过构造一个状态观测器来重构系统的状态, 建立基于重构状态的线性控制律. 然后, 通过独立地考虑重复控制系统的连续控制过程与离散学习行为, 给出基于状态观测器和重构状态反馈的连续/离散二维混合模型. 针对这个混合模型, 运用二维Lyapunov泛函方法, 以线性矩阵不等式(Linear matrix inequality, LMI)的形式给出重复控制系统存在重复控制器和状态观测器的充分条件, 所给条件可用Matlab工具箱方便地求解. 数值仿真验证了本文所提方法的有效性.     

一种多目标进化算法解集分布广度评价方法

解集分布广度评价是多目标进化算法性能评价中的重要研究课题.作者提出了一种在未知Pareto最优面情况下解集分布广度评价方法(Spread Indicator,SI).不同于已存在的评价方法考虑极端个体,该方法利用边界解集对非支配集分布范围进行评价.对非支配集中边界解的性质和特征进行了详细的分析,讨论了边界解与极端解之间...     

Estimation of the resident’s additional dose in bone-coal mining areas of the five provinces

1 Introduction In the National Investigation of Natural Radioac-tive Levels (abbreviated as “investigation of levels” hereinbelow) during 1983 to 1990, it is found that the specific activities of radionuclides in bone-coal are relatively high. The increase of radioactive level in the environment and the rise of the public accepted dose might be caused by some artificial activities, which include mainly mining and utilizing spontaneously bone-coal by local peasants, producing bone-coal cind…     

MPLS中的Loop避免机制及其Java实现

本文介绍了MPLS中回路问题的主要解决方法，分析了COLORED THREAD算法的主要思想，并使用Java技术实现了该算法，文中给出了Java实现的结构和主要技术要点，并提出了Java中实现MPLS节点时间调度的方法。     

一种新的网络业务流的多重分形小波模型

针对当前Internet上日益复杂的网络业务流和视频流，文章提出了一种新的多重分形小波模型．与普通的多重分形小波模型(Multifractal Wavelet Model，MWM)不同的是，该文提出的新模型在各个时间尺度上对小波系数都依据源数据尺度系数的边缘分布作了修正，这样确保新模型能在不同的时间尺度上拟合源数据的分布．决定网络业务流的排队分析特性的是一个关键时间尺度(Critical Time Scale，CTS)，CTS是随着缓冲区的容量和节点传输速率的变化而变化的，该文提出的模型能描述几乎各个时间尺度的业务流特性，因此能适应各种不同情况的缓冲区的排队分析．同时，新模型也继承了传统MWM的一些优良特性，比如能描述业务流的多重分形特征以及能确保最终结果始终是非负等等．最后通过对视频业务流和网络业务流的仿真实验与排队分析验证了该模型的有效性．     

几种润滑剂对温压工艺的影响

温压工艺的技术关键之一是润滑剂 ,其主要作用是减小压制过程中粉末颗粒与模壁之间及粉末颗粒之间的摩擦 ,增大有效压力 ,从而使压坯密度相对于传统压制工艺明显提高。不同润滑剂的润滑效果不同 ,最佳压制温度也有差异。本文选用 3种不同的润滑剂 ,在不同温度、压力条件下采用温压技术制备铁基粉末冶金材料 ,研究了压坯密度的变化规律和它的力学性能 ,探讨了润滑剂对温压工艺的影响     

Delay-dependent criteria for robust stability of time-varying delay systems

This paper deals with the problem of delay-dependent robust stability for systems with time-varying structured uncertainties and time-varying delays. Some new delay-dependent stability criteria are devised by taking the relationship between the terms in the Leibniz-Newton formula into account. Since free weighting matrices are used to express this relationship and since appropriate ones are selected by means of linear matrix inequalities, the new criteria are less conservative than existing ones. Numerical examples suggest that the proposed criteria are effective and are an improvement over previous ones.     

Design of a discrete-time output-feedback based repetitive-control system

This paper deals with the problem of designing a robust discrete output-feedback based repetitive-control system for a class of linear plants with periodic uncertainties. The periodicity of the repetitive-control system is exploited to establish a two-dimensional (2D) model that converts the design problem into a robust stabilization problem for a discrete 2D system. By employing Lyapunov stability theory and the singular-value decomposition of the output matrix, a linear-matrix-inequality (LMI) based stability condition is derived. The condition can be used directly to design the gains of the repetitive controller. Two tuning parameters in the LMI enable the preferential adjustment of control and learning. A numerical example illustrates the design procedure and demonstrates the validity of the method.