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通过问卷对南昌地区六所本科院校的1 200名大学生的网络使用情况进行调查,发现平均每天上网的时间、网恋的经历、上网费用的预算与网络依赖的程度存在显著的正相关关系,每周户外运动次数与网络依赖程度存在显著的负相关关系。同时,大部分大学生的上网动机为娱乐和游戏,上网的地点基本集中在寝室和校内的网吧,上网的时间段为18:00~23:00之间。根据调查情况,对大学生健康使用网络提出了相应的建议。 相似文献
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针对现有可靠性分析方法的局限性与不足,首先,根据挡土墙岩土力学参数取值的区间性特征,引入区间分析理论,视挡土墙岩土力学参数为区间变量,在确定出挡土墙稳定可靠性分析的合理功能函数基础上,建立出基于区间理论的挡土墙结构稳定非概率可靠性计算模型;其次,针对区间运算结果扩张问题,引入区间组合法和改进区间截断法,建立出挡土墙稳定性非概率可靠性分析的区间运算方法,进而建立出基于区间理论的挡土墙稳定性非概率可靠性分析方法;最后,将该方法应用于工程实例,结果表明了本文方法的合理性与可行性,并探讨了岩土力学参数对挡土墙稳定性非概率可靠性指标的影响规律,具有一定的工程参考价值。 相似文献
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Stability analysis of subgrade cave roofs in karst region 总被引:2,自引:0,他引:2
According to the engineering features of subgrade cave roof in karst region, the clamped beam model of subgrade cave roof in karst region was set up. Based on the catastrophe theory, the cusp catastrophe model for bearing capacity of subgrade cave roof and safe thickness of subgrade cave roof in karst region was established. The necessary instability conditions of subgrade cave roof were deduced, and then the methods to determine safe thickness of cave roofs under piles and bearing capacity of subgrade cave roof were proposed. At the same time, a practical engineering project was applied to verifying this method, which has been proved successfu1ly. At last, the major factors that affect the stability on cave roof under pile in karst region were deeply discussed and some results in quality were acquired. 相似文献