预腐蚀对某型飞机42框横梁疲劳寿命的影响

采用周期浸润加速腐蚀试验的方法,对某型飞机42框横梁模拟件分组进行了不同时间的加速预腐蚀试验,并通过随机载荷谱下的疲劳试验获得了预腐蚀后模拟件的疲劳寿命。结果表明,在加速腐蚀时间不大于300小时的情况下,预腐蚀对42框横梁结构模拟件疲劳寿命的影响不明显。     

清末贵州状元夏同龢书法赏析

清末贵州状元夏同龢“工文善书,有名当世.”其书法作品多为楹联、扇面等赠人之作.贵州省博物馆有其两副楹联,其中的行楷八言联取势自然,体态有度;苏州博物馆有其书法扇面一帧,其书娟秀清丽,温雅可人,均可窥见夏同龢书法严谨整饬、端庄平正的艺术风格.     

肖邦《g小调第一叙事曲》音乐内涵解蔽

肖邦《g小调第一叙事曲》充满了悲剧性色彩,作品优美悲伤的歌调、甜蜜柔美的抒情、轻盈华丽的炫技、灿烂丰美的热情、戏剧化的急板以及悲剧性的结尾都极富叙事性特点,而其中的民族性、英雄性与悲壮性更是作品所潜藏的深刻音乐内涵。     

别样的反抗——读王安忆的小说《大学生》

农民“大瞎生”主动离开土地,想要融人城市,但又不想凭借自己的勤劳与智慧在城市中立足,而只是以城市人自居混迹城市.所遭遇的是被拒城市身份,又被乡村抛弃的尴尬的无身份境遇.为了摆脱这种孤立、绝望的处境,他只能选择反抗,寻求自我价值的实现,证明自己的存在.     

兰州市小学、初中校园足球活动开展状况调查分析

我国青少年＂校园足球＂联赛启动三年来,兰州市小学、初中校园足球活动取得了长足的进步。运用文献资料法、问卷调查法、专家访谈法、数理统计法对兰州市＂校园足球＂活动的开展现状进行了详细的调查,分析其开展过程中存在的经验与不足,找出制约因素,并针对存在的问题提出对策和建议。     

Paying Teachers According To Student Achievement: Questions Regarding Pay-For-Performance Models in Public Education

In an effort to correct for perceived deficiencies in the No Child Left Behind Act, value-added models were proposed as a way to find out how much students learned in schools and classrooms throughout the school year. What has garnered much controversy regarding the value-added model, however, is the attempt to link pay and tenure to performance. In this article, a theoretical framework is introduced that examines the likely success of using value-added assessments as a pay-for-performance tool. After applying the theory, the author suggests that caution should be used when utilizing value-added assessments to pay teachers for student learning.     

兰州市城市环境与建设生态城市的理性思考

城市是人类文化精华的积淀,是人类生活的家园.兰州市作为甘肃省首府城市,自改革开放以来在社会、经济等各个方面都取得了令人瞩目的成就,可是随之而来的环境问题,影响了兰州城市环境的可持续发展,成为了当前研究的热点问题.文章以科学发展、构建和谐社会为目标,针对兰州市生态城市建设中面临的环境污染严重、绿地系统脆弱、城市空间狭小、城市交通拥挤等问题,探讨了在城市发展中要全面提高兰州城市环境质量,加快建设城市的绿地系统,加强城市基础设施建设,提高城市文化品位,将兰州市建设为一个绿色和谐、舒适健康、发展公平的优质生态城市.     

Stabilizing region of PDμ controller for fractional order system with general interval uncertainties and an interval delay

This paper concentrates on computing the stabilizing region of PD^μ controller for fractional order system with general interval uncertainties and an interval delay. The stabilizing region means the complete/approximate set of PD^μ controllers that stabilize the given closed-loop control system. General interval uncertainties refer to both coefficients and orders of the fractional system suffer from interval uncertainties. Interval delay indicates that the delay also vary in a specified interval.Firstly, a method is presented to calculate the stabilizing region for general interval fractional system with an interval time-constant delay. Based on a novel mapping function and the concept of critical controller parameters, the stabilizing region can be determined numerically. Secondly, the stabilizing region computation problem for general interval fractional system with an interval time-varyingdelay is considered. By applying a revised small-gain theorem, the stabilizing region can be calculated like the time-constant delay case. Thirdly, two alternative methods are proposed to improve the computational efficiency of stabilizing region calculation. Both methods can reduce the number of polynomials which are used to determine the stabilizing region. Examples are followed to illustrate the proposed results.