最值求解技巧:巧变四数

在用基本不等式求最值时,大家都熟悉一个口诀:"一正二定三相等",但是有许多学生在怎样保证定值和相等时不知道该如何变形.为了解决学生的困难和困惑,我根据自己的经验,概括为两句口诀:"一正二定三相等,巧变四数定乾坤".     

论惠特曼诗中的三大主题

瓦尔特.惠特曼(Walt Whitman 1819-1892)是第一个走向世界文坛的美国诗人、是一位伟大而真诚的民主主义战士。他的诗以赞美人和自然,歌颂平等、民主、自由为主调,他自信自立、崇尚自由、平等、民主的个性都鲜明地反映在《草叶集》(Leaves of Grass)中。     

产业化,我们如何面对

高等教育具有产业性质,然而,中国高等教育产业水平还很低。产业化的积极意义是无可争议的。没有高等教育产业化,就没有高等教育的深入改革和发展。任何“化”的提法都表示一种相对变化,产业化也是指一种相对变化,并非绝对化。教育平等与公正在产业化进程中有更大可能成为现实,教育伦理也可以在产业化进程中上扬。这就看我们如何看待产业化。大学精神与产业精神在高水平上的融合,这才是大学工作的真正艺术。     

Preferential normal fuzzy subgroups

In this paper we consider the notion of normality on preferential fuzzy subgroups of a finite group G and define the associated concept of a normal pinned-flag. We discuss the preferential equality of quotients and products of normal preferential fuzzy subgroups. Further normalizers of fuzzy subgroups under preferential equality are briefly dealt with. Examples are given to illustrate the structure of preferential normal fuzzy subgroups and normal pinned-flags.     

A globally and quadratically convergent primal–dual augmented Lagrangian algorithm for equality constrained optimization

We present a primal–dual augmented Lagrangian method to solve an equality constrained minimization problem. This is a Newton-like method applied to a perturbation of the optimality system that follows from a reformulation of the initial problem by introducing an augmented Lagrangian function. An important aspect of this approach is that, by a choice of suitable updating rules of parameters, the algorithm reduces to a regularized Newton method applied to a sequence of optimality systems. The global convergence is proved under mild assumptions. An asymptotic analysis is also presented and quadratic convergence is proved under standard regularity assumptions. Some numerical results show that the method is very efficient and robust.     

收入公平、教育、生态一幸福效率与环境造成的疾病负担的实证分析

研究了经济增长方式对人们健康的影响,选用环境造成的疾病负担作为应变量,实证分析了该指标与收入、收入公平、教育、生态一幸福效率等自变量的关系,从理论的角度证明了经济增长是环境造成的疾病负担减轻的一个必要条件,但更强调了其他变量（收入公平、教育、生态一幸福效率）与应变量的相关关系．研究表明：社会分配越公平、教育普及程度和生态一幸福效率越高,环境造成的疾病负担越低,从而证明了一个国家的经济发展方式对国民健康有实质的影响．     

瑞典的职业教育--专业与课程设置分析

瑞典的职业教育，专业和课程设置富有灵活性。以提供基础教育为理念，重视学生基本素质、基本能力的提高。学生享有高度选择自由。     

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.     

基于相量量测的等式约束二阶段状态估计模型

利用PMU的量测信息实现系统的动态可观测,考虑PMU数据刷新时间快的特点,在R.F.Nuqui的动态监测模型的基础上建立了适合静态估计的基于等式约束二阶段估计模型。该模型将PMU和SCADA的量测数据共同用于非线性估计,采用零注入节点功率作为等式约束条件来提高估计精度,然后对非线性估计的结果和PMU的支路电流相量进行线性估计。模拟了当系统某节点负荷持续变化时,利用等效导纳法对非线性区域节点状态量进行估计,最后采用IEEE 14和57节点系统算例对提出的模型进行了验证。