二次方三项式线性齐次微分方程的解法     

孙长军 《荆门职业技术学院学报》2006,21(3):59-61

通过把线性齐次微分方程x2y(n) 2nxy(n-1) n(n-1)y(n-2)=0化为可逐次积分的线性微分方程,找出了它的通解形式,给出了严格的证明,并将其推广,得到x2y(n) (x2 2nx)y(n-1) [2(n-1)x n(n-1)]y(n-2) (n-1)(n-2)y(n-3)=0的通解.  相似文献   

Fresnel圆屏衍射的计算机模拟演示     

游开明  薛莉  陈列尊  王友文  戴志平 《衡阳师范学院学报》2012,33(3):40-43

基于Huygens-Fresnel衍射积分和Babinet原理,利用Hankel变换算法及球面波因子处理方法,在普通PC上使用MFC编程较好地实现了Fresnel圆屏衍射的计算机模拟演示。演示中,Fresnel圆屏衍射的光强剖面分布、衍射图样和中心光强分布分别随光的传输距离和波长及圆屏半径的改变而变化,光的传输距离和波长及圆屏半径由三个滚动条分别控制。  相似文献   

模糊自校正PID液位串级控制系统设计与仿真   总被引：1，自引：0，他引：1  

林屹  叶小岭 《实验室研究与探索》2010,29(3)

针对双容水箱液位控制问题,探讨了模糊控制理论在液位控制系统中的应用,提出了基于模糊自校正PID的串级液位控制方案,设计了一种模糊自校正PID控制器,并在此基础上对该双容水箱液位在3种不同控制方案,即单回路PID控制、串级控制以及基于模糊自校正PID的串级控制下的控制效果进行了Simulink仿真研究。结果表明,相对于常规单回路PID以及常规串级控制,基于模糊自校正PID的串级控制系统在超调量、调节时间、抗干扰等方面有更好的控制品质。  相似文献   

Sexual dimorphism in bone–muscle relationship in young adults     

Vera Zymbal  Kathleen F. Janz  Fátima Baptista 《Journal of sports sciences》2017,35(24):2433-2438

The purpose of this study was to analyse associations between lean soft tissue (LST), a surrogate of skeletal muscle mass and key fracture-related geometric characteristics of the proximal femur. Moreover, we examined the role that muscle played on the proximal femur geometry in response to physical activity (PA). Participants were 83 young adults. Leg LST (exposure) was assessed by dual energy X-ray absorptiometry (DXA). Proximal femur geometry was derived from a left hip DXA scan. Geometric variables (outcomes) included the femoral neck axis length (FNAL), the femoral neck width (FNW), the neck–shaft angle and FNW|FNAL (an index of robustness). PA was evaluated by accelerometry. Linear regression was used to analyse relationships. Additional exposure variables included body height and mass. In males, leg LST explained 17.4% of variation in FNAL (P < 0.001) and 15% in FNW (P = 0.015). In females, it explained 8.8% of the variance in FNAL (P = 0.020). Associations remained significant in males, but not in females, when vigorous PA was added to the models. These results suggest that public health approaches to promote PA may be particularly important in females since vigorous PA seems to convey advantages in femur geometry and consequently in bone strength.  相似文献   

Knots in the Fourth Dimension     

《Cultural and Social History》2013,10(1):31-49

ABSTRACT

The article analyses a debate that preoccupied the Russian press in the winter of 1878/9. Writers, journalists and scientists discussed whether mathematics could explain spiritualist séance phenomena. At its core, this was an assessment of social change and a debate about the ambiguity of modern life. While spiritualists hoped to bridge the divide between science and religion, subjectivity and objectivity, their opponents feared that séance phenomena and modern mathematics undermined a rationalist world-view that was endowed with reliability and universal truth. That no agreement could be reached indicates that the post-reform public sphere had become truly pluralist and modern.  相似文献   

从体育创造的三个层面看北京“新奥运”的三大理念——谈社区体育的“三个一体化”     

马亦梅 《吉林体育学院学报》2004,20(1):20-20,24

体育创造铸就了北京奥运会的三大理念,如何借助北京“新奥运”的理念,推进社区体育的健康发展,就此提出创建社区体育“三个一体化”的新思路。  相似文献   

"三线共点"的常用证明方法     

王贵军 《天水师范学院学报》2002,22(2):56-58

从仿射几何学与射影几何学的基本方法出发,简述了"三线共点"问题的一些基本的证明方法.  相似文献   

论高职市场营销专业“五位一体”实践教学模式的构建     

陈民利 《唐山职业技术学院学报》2007,(1)

能力培养是高职教育的特色与关键。高职市场营销专业人才能力的培养需要建立系统的可操作的实践教学模式。"课程实训、模拟实训、专题实训、营销实战、社会兼职"五位一体的实践教学模式是培养学生能力的有效途径。  相似文献   

再谈反函数的积分     

石岚 《陕西国防工业职业技术学院学报》2007,(3)

运用反函数积分公式求积分,使得一些函数的积分变得简单。  相似文献   

赛艇兴波阻力的计算   总被引：2，自引：0，他引：2  

葛新发  马勇  郑伟涛  韩久瑞 《武汉体育学院学报》2004,38(4):64-67

回顾了船舶兴波阻力计算的发展历程,采用Michell积分计算赛艇兴波阻力是比较理想的。通过对两条双人赛艇和一条单人艇的计算及分析表明:赛艇的兴波阻力随速度的增加会出现阻力的"峰点"和"谷点"。较高的速度有利于专项技术的训练,中等速度有利于专项力量的训练,速度太低,训练就不会达到很理想的效果。  相似文献