排序方式: 共有37条查询结果,搜索用时 421 毫秒
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自由衰减试验仍是目前最为有效且常用的估算横摇阻尼系数的方法.横摇阻尼系数的估算精度对于船舶横摇运动的预报起着至关重要的作用.通常采用所谓的消灭曲线法来分析自由横摇衰减数据.该方法的一个不足之处在于其推导是基于忽略了非线性恢复力项的自由横摇运动方程.另一方面,考虑更多非线性成分的能量法能够纳入该因素影响但在实施过程中较为复杂.文中提出了一种改进型的消灭曲线法,能够纳入船体非线性恢复力项的影响.所提出的方法形式简单且相比能量法更易于实施.数值试验证明了改进型消灭曲线法的正确性,并展现了其相对传统消灭曲线法所具有的优势. 相似文献
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采用数理统计原理,运用SPSS软件对陕西省7条高速公路交-竣工平整度数据进行分析,得出了陕南、关中和陕北地区路面平整度衰变幅度均值分别为0.39m/km、0.28m/km和0.24m/km,这也将作为计算竣工验收推荐值的依据;再基于交-竣工平整度变化规律,建立了平整度竣工验收推荐值的计算公式:IRIju=IRIji+IRIs,可为今后平整度竣工验收标准提供有效的理论依据。 相似文献
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非药式水下爆炸冲击波特性数值模拟研究 总被引:1,自引:0,他引:1
非药式水下爆炸冲击波模拟实验可以克服炸药式水下爆炸耗费大、危险性高等困难,对研究水下爆炸冲击波载荷作用下舰艇的动态响应与损伤具有重要意义。本文运用实验与仿真相结合的方法对非药式水下爆炸冲击波特性进行了研究,分析了不同飞片质量、速度及活塞质量对冲击波载荷强度和衰减时间常数的影响规律,建立了预测非药式水下爆炸冲击波初始峰值和初始冲击波衰减时间常数的经验公式。结果表明:水下爆炸初始冲击波峰值与飞片的初始撞击速度成正比,与飞片及活塞的质量无关。初始冲击波的衰减时间常数仅随飞片和活塞质量的改变而改变,飞片的初始撞击速度对其无显著影响。 相似文献
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梁波 《大连铁道学院学报》2009,(4):111-112
研究了量子漂移扩散模型解的指数衰减.该模型来自于量子流体动力学模型,是一个非线性四阶抛物型偏微分方程组,由于比较原理对于四阶偏微分方程不再成立,进而最大模估计成为本质困难.利用熵函数的方法,结合差分法,能量估计,梅造差分方程解的迭代.从而在时间增大时,得到解在L^1意义下以指数速度衰减到常定态. 相似文献
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基于老旧船的船体腐蚀状况,运用剖面模数概念,分析了腐蚀对船舶强度的影响,提出了一些保证船舶强度的措施,为加强船舶的保养工作提供一些参考。 相似文献
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在山西省某条高速AC-13混合料施工过程中现场随机取样并作标记,根据试验得到混合料沥青含量和级配。次日在标记路段钻芯取样计算压实度,并且测定路面构造深度(TD),利用Matlab分析构造深度与沥青含量、级配的关系,得出AC-13沥青混合料路面构造深度可以通过其与沥青含量和级配的关系得出;分别在路面通车后7 d内、半年内、一年内实测路面相关路段的构造深度,分析构造深度在交通量和通车时间共同作用下的衰变规律,在通车半年时间内构造深度衰变量在14.1%~16.3%之间,通车半年到一年时间内构造深度衰变量在5.5%~9.0%之间。 相似文献
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Transportation specialists, urban planners, and public health officials have been steadfast in encouraging active modes of
transportation over the past decades. Conventional thinking, however, suggests that providing infrastructure for cycling and
walking in the form of off-street trails is critically important. An outstanding question in the literature is how one’s travel
is affected by the use of such facilities and specifically, the role of distance to the trail in using such facilities. This
research describes a highly detailed analysis of use along an off-street facility in Minneapolis, Minnesota, USA. The core
questions addressed in this investigation aim to understand relationships between: (1) the propensity of using the trail based
on distance from the trip origin and destination, and (2) how far out of their way trail users travel for the benefit of using
the trail and explanatory factors for doing so. The data used in the analysis for this research was collected as a human intercept
survey along a section of an off-street facility. The analysis demonstrates that a cogent distance decay pattern exists and
that the decay function varies by trip purpose. Furthermore, we find that bicyclists travel, on average, 67% longer in order
to include the trail facility on their route. The paper concludes by explaining how the distance decay and shortest path versus
taken path analysis can aid in the planning and analysis of new trail systems.
Kevin J. Krizek is an Associate Professor of Planning and Design at the University of Colorado where he directs the Active Communities/Transportation Research Group. His research interests include land use-transportation policies and programs that influence household residential location decisions and travel behavior. He has published in the areas of transportation demand management, travel behavior, neighborhood accessibility, and sustainable development. He earned a Ph.D. in Urban Design and Planning and M.S.C.E. from the University of Washington in Seattle. His master’s degree in planning is from the University of North Carolina at Chapel Hill and his undergraduate degree is from Northwestern University. Ahmed El-Geneidy is a Post-Doctoral research fellow at the Department of Civil Engineering, University of Minnesota and Humphrey Institute of Public Affairs. El-Geneidy’s research interests include transit operations, travel behavior, land use and transportation planning, and accessibility/mobility measures in urban areas. He earned B.S. and M.S. degrees from the Department of Architectural Engineering at the University of Alexandria, Egypt, and continued his academic work at Portland State University, where he received a Graduate GIS Certificate and earned a Ph.D. in Urban Studies from Nohad A. Toulan School of Urban Studies and Planning. Kristin Thompson was a research assistant with ACT and currently works for Metro Transit in Minneapolis, Minnesota. 相似文献
Ahmed El-GeneidyEmail: |
Kevin J. Krizek is an Associate Professor of Planning and Design at the University of Colorado where he directs the Active Communities/Transportation Research Group. His research interests include land use-transportation policies and programs that influence household residential location decisions and travel behavior. He has published in the areas of transportation demand management, travel behavior, neighborhood accessibility, and sustainable development. He earned a Ph.D. in Urban Design and Planning and M.S.C.E. from the University of Washington in Seattle. His master’s degree in planning is from the University of North Carolina at Chapel Hill and his undergraduate degree is from Northwestern University. Ahmed El-Geneidy is a Post-Doctoral research fellow at the Department of Civil Engineering, University of Minnesota and Humphrey Institute of Public Affairs. El-Geneidy’s research interests include transit operations, travel behavior, land use and transportation planning, and accessibility/mobility measures in urban areas. He earned B.S. and M.S. degrees from the Department of Architectural Engineering at the University of Alexandria, Egypt, and continued his academic work at Portland State University, where he received a Graduate GIS Certificate and earned a Ph.D. in Urban Studies from Nohad A. Toulan School of Urban Studies and Planning. Kristin Thompson was a research assistant with ACT and currently works for Metro Transit in Minneapolis, Minnesota. 相似文献