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作用力功与反作用力功的区别与联系
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作者 李文华 《中国科技经济新闻数据库 教育》 2017年第1期309-309,共1页
作用力与反作用力发生在相互作用的两个物体之间,作用力与反作用力的功的问题实质上就是寻找力的方向上的位移问题。本文从几个实例出发,就有关作用力功与反作用力功的几种类型进行了分析,以帮助同学们理清思路,提高分析问题的能力。
关键词 作用力功 作用力功
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弹性势能公式E_p=1/2kx^2的x问题 被引量:1
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作者 张世良 王薇 《北京联合大学学报》 CAS 1999年第2期94-97,共4页
弹性势能是大学物理中重要的物理概念,也是教学难点。在目前教学中,由于某些教材及教师对系统内成对保守内力做功、参照系选取等内容强调不足,使学生不能准确理解弹性势能概念。如果通过对公式Ep=12kx2中的x是否是弹簧位移... 弹性势能是大学物理中重要的物理概念,也是教学难点。在目前教学中,由于某些教材及教师对系统内成对保守内力做功、参照系选取等内容强调不足,使学生不能准确理解弹性势能概念。如果通过对公式Ep=12kx2中的x是否是弹簧位移的讨论和反作用力功的讨论,来理解势能是物体系的势能,势能等于系统内所有对保守内力做功之和的负值,可能就容易多了。这种教学途径不失为帮助学生理解弹性势能这个教学难点的一个方法。 展开更多
关键词 弹性势能 弹簧位移 作用力功 势能
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Effects of Bisoprolol on the ventricular function and hemodynamics in patients with atrial fibrillation and chronic heart failure
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作者 舒茂琴 何国祥 +2 位作者 宋志远 席瑞霞 张萍 《Journal of Medical Colleges of PLA(China)》 CAS 2004年第5期302-306,共5页
Background: Recent data suggest that beta-blockers can be beneficial in patients with chronic heart failure (CHF). Atrial fibrillation (AF) is present in a significant number of patients with CHF and is associateing w... Background: Recent data suggest that beta-blockers can be beneficial in patients with chronic heart failure (CHF). Atrial fibrillation (AF) is present in a significant number of patients with CHF and is associateing with significant morbidity and increasing mortality rates. Thus it is necessary to establish therapy to improve the poor prognosis in this high-risk population, but a specific benefit of beta-blockers to the subset with concomitant AF and CHF has been little demonstrated. Objective: To examine the effects of Bisoprolol (6 months treatment) on the ventricular function and hemodynamics in patients with AF and CHF. Methods: 84 patients with stable CHF (NYHA≤Ⅲ class) and AF were assigned to Treated Group( n = 37) or Control group Ⅰ ( n = 22, 24-hour heart mean rate < 70/min) or Control Group Ⅱ ( n = 25, 24-hour heart mean rate ≥ 70/min) . All patients were given the basic therapy for CHF, and Treated Group received Bisopolol. Clinical and echocardiographic variables were measured in 3 groups at baseline and after 6 months, and the results were compared . Results: After 6 months of treatment with Bisoprolol, left ventricular ejection fraction (LVEF) and NYHA class had significandy improved (P < 0.05), and a trend towards a reduction in combined end point of death or CHF hospitalization was also observed (P < 0.20) in Treated Group; The increase of LVEF in Treated Group were associated with a reduction in mitral regurgitation degree and left atrial volume; The heart rate in mean 24-hour and at peak exercise decreased in Treated Group, but were similar to that in Control Group Ⅰ. Conclusion: 6 months of Bisoprolol therapy resulted in an improvement in the NYHA class and LVEF, and also showed a trend towards a reduction in hospitalization or death. The beneficial effects of Bisoprolol on patients with AF and CHF may be partly mediated by improvement of ventricular diastolic function. 展开更多
关键词 BETA-BLOCKER heart failure ventricular dysfunction atrial fibrillation
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