一种双旋翼控制系统的建模与仿真

对一种复杂的多输入多输出控制系统—双旋翼系统进行了研究。在详细、准确地进行运动学和动力学分析的基础上,建立了比较完备的双旋翼系统数学模型,并对双旋翼控制系统的姿态控制进行了初步仿真,并给出了仿真结论。     

适应社会稳定工作的需要深化高校"两课"教学改革的探索和实践

本文分析了21世纪我国高校"两课"教学所面临的新挑战,比较系统地总结了为适应新世纪社会稳定工作的需要,深化"两课"教学改革的一些实践经验,在教学改革的指导思想、教学原则上以及在教学观念、教学内容、教学方法、教学手段、教学环节、教学管理体制等方面的改革上进行了有益的探索.     

应用双剪理论计算钢管混凝土需注意的几点问题

针对钢管混凝土的复杂受力特性及目前计算钢管混凝土承载力时双剪统一理论的应用条件,通过对构件受压过程的理论分析得出应用该理论时常被工程忽视的几点关键问题。本文的分析有助于对钢管混凝土受力行为的深入理解,并为后续工作的展开提供指导。     

Sport disciplines,types of sports,and waist circumference in young adulthood – a population-based twin study

Purpose: The benefits of physical activity (PA) in preventing abdominal obesity are well recognized, but the role of different sport disciplines remains open. We aimed, therefore, to investigate how participation in different sport disciplines, and the number and types of sports engaged in are associated with waist circumference (WC) in young adulthood. Methods: This population-based cohort study comprised 4027 Finnish twin individuals (1874 men), with a mean age of 34 y (32–37), who answered a survey, including self-measured WC. We extracted the number and identified the types (aerobic, power, and mixed) of the different sport disciplines respondents reported participating in. Results: The number of sport disciplines participated in was inversely associated with WC, the linear decrease averaging 1.38?cm (95% CI 1.10–1.65) per each additional sport discipline. The result persisted after adjustment for the main covariates, such as volume of PA and diet quality. Among dizygotic twin pairs discordant for sports participation (0–2 vs. 5 or more disciplines), the mean within-pair difference in WC was 4.8?cm (95% CI 0.4–9.1) for men and 11.2?cm (95% CI 4.4–18.0) for women; among discordant monozygotic pairs, no differences were observed. In men, all three types of sports were individually associated with smaller WC, while in women, only mixed and power sports showed this association. Conclusions: Participation in several sport disciplines and sport types was associated with smaller WC among young adults in their mid-30s. Shared genetic background may explain some of the associations.     

文史本根生 相生何太急——浅谈文学与史学出现早晚问题

文学和史学的起源关系是一个古老的问题。文史不分家是我国古代治史的传统。随着学术的日益发展则分科愈精密,此前本是一家之体,而今蔚然成一独立学科者,比比皆是。就史学和文学这两大知识门类来看,无论是在中国的学术传统中,还是在西方的学术背景下,两者间的关系既呈现出划然可分的边界,又往往互相含摄、彼此纠缠。自从历史学被划入科学的范畴后,史学和文学之间的问题就尖锐起来。本来是孪生兄弟的史学和文学,如今却在争论何者更早出现,这个现象值得引起我们的注意。在这里,我主要以中国的史学与文学为探讨对象进行探讨。     

用辛达拉姆筛法探讨孪生素数无穷多

在已有文献研究结论的基础上,用辛达拉姆（Snndaram）发明的一种求素数新筛法探讨孪生素数是否无穷多问题,得到了一些新的结论．     

Goldbach问题和孪生素数问题的证明

本文给出了素数和素数对计数问题的几个公式，在此基础上，证明了Goldbach问题和孪生素数问题。     

对称双塔连体结构的动力特性分析

依据现行抗震设计规范,运用三维有限元软件ANSYS,对某33层大底盘对称双塔连体结构进行动力特性分析。结果与未设连体的双塔结构进行比较,对不同高度设置连体进行讨论。结果表明,增设连体后双塔的自振频率提高,扭转振型更加丰富,且运动和变形得到了统一和协调。     

双壁波纹管滤水器轴向拉力破坏试验研究

为了探索双壁波纹塑料管用作水井井壁管和滤水器安装井管时的轴向抗拉能力,本研究以PVC双壁波纹管加工成的双壁波纹管滤水器圆管和条板材料为研究对象、并对其管接头采用密封圈加固,螺钉加固,铁丝绑扎,管箍铁件连接四种不同加固方式,在万能拉力机上进行拉力对比试验,结果表明：开有条形孔的管材的抗拉力明显低于末开孔的,开孔率越大,抗拉力越低;3个相同试件破坏时的拉力最大为3kN,最小为2．93kN,差值为0．07kN。相差不大;开孔率相同的板状试件．波纹糟中开孔的抗拉力较棱上开孔的高28％～63％;单纯承插连接,接头抗拉力太小,不能用于井管连接;螺钉加固,铁丝绑扎加固的接头抗拉力比较强,且成本低,管箍铁件加固抗拉力大,但成本高,故建议采用承插螺钉加固与铁丝绑扎加固用于浅井和中深井。管箍铁件加固用于深井。     

Differential prognosis of reading-disabled children as a function of gender,socieconomic status,IQ, and severity: A longitudinal study

Data from 104 reading-disabled subjects tested on two occasions over an average interval of nearly five years were used to test hypotheses of differential prognosis for reading performance and symbol-processing speed as a function of gender, socioeconomic status, general intelligence, and initial severity. With respect to reading performance, significant main effects due to intelligence and severity were found. Moreover, the interaction between initial severity and test occasion was significant for reading performance due to a greater rate of improvement for the more severely disabled subjects. No evidence was obtained, however, for differential developmental rates as a unction of gender, socioeconomic status, or intelligence for this measure. With regard to symbol-processing speed, significant main effects were found due to gender, intelligence, and severity, whereas developmental rates were found to differ as a function of gender and socioeconomic status.