解三维水翼绕流的下潜涡环栅格法

在包含于机翼表面内的某次表面及尾涡面上分布法向偶极子,在翼面上满足物面边界条件,建立了解三维机翼绕流的下潜涡环栅格法.考虑到非线性的自由液面边界条件,用下潜涡环栅格法求解水翼绕流问题.通过算例验证了方法的正确性和程序的可靠性.本方法可用于水翼及水下安定翼和各种舵的水动力计算.     

潜艇内波尾迹物理场在海面映波量值的确定

采用Tuck的方法,具体计算了国外有代表性的潜艇在海洋中内波尾迹物理场垂直上传到海面上的映波的量值,并对映波波幅随艇半径、艇长度、艇速和艇后距的关系作了分析.     

The Size Effects on Process Design of Micro Deep Drawing

This paper suggested to reformulate cylindrical deep drawing parameters with dimensionless form. A diagram, in which a feasible zone is drawn to bound both the maximal allowable tension and compression stress during the deep drawing process, was established. Since it is presented in a dimensionless form, it may be applied for both conventional and micro deep drawing. Cylindrical cup deep drawing was taken as an example to show the dimensionless process design method. In addition, the size effects should be taken into account. Two kinds of size effects on micro deep drawing were investigated, which can be explained by surface layer model and strain gradient model. Numerical simulations were carried out to compare the strain distribution with or without consideration of size effect.     

既有铁路桥墩健全度评估和试验方法研究

铁路桥梁检定部门主要依据《铁路桥梁检定规范》对铁路桥墩进行状态评估。由于桥墩在列车激励下的振幅随列车的种类、速度、轴重以及轨道不平顺状态的不同而变化,所以利用振幅指标难以定量判断桥墩的损伤。为此,通过理论分析、数值模拟计算、实验室试验和现场试验,对冲击振动试验法进行系统的研究,提出基于自振频率指标的桥墩健全度评估方法。主要研究内容如下。(1)从理论上给出推导冲击振动试验法的基本原理,编制冲击振动试验信号处理的计算机程序。(2)通过实验室试验和悬臂墩、简支梁、单墩桥梁体系、多墩多梁桥梁体系及空间桁梁模型等数…     

对转螺旋桨升力面设计方法

本文针对对转螺旋桨这类组合式推进器的设计问题,采用了升力面设计方法进行设计,在设计过程中通过前后桨的相互迭代求出彼此间的诱导速度,以此来考虑它们之间的相互作用,并采用此方法作了一对对转螺旋桨的设计,同时应用面元法进行了水动力预报。     

三维边坡稳定性分析的一种适用方法

基于空间曲面上一点的应力关系、曲面至边坡表面土柱上力的微分平衡方程、力矩平衡方程,只需要一个假定条件,得出了一种广泛适用的三维边坡稳定性分析法,并讨论了方法应用中的有关问题。算例表明,该方法计算结果是合理的,具有广泛的应用意义。     

基于应力波反射法的桥梁竖向预应力筋管道注浆效果检测

文章结合某连续刚构桥,通过分析应力波反射法的检测原理,试将该检测方法用于桥梁竖向预应力筋波纹管注浆效果的评价,结果表明采用该方法检测桥梁单根预应力筋管道注浆密实度是一种高效、便捷、经济的检测方法。     

冰区航行船舶推进器特殊性分析

  目的  为了准确评估破冰船在平整冰区航行时连续破冰过程中所受的冰阻力,同时了解不同预报方法的特点,采用经验公式法、数值模拟法以及船模试验法,对破冰船在平整冰中连续航行时的冰阻力进行预报。  方法  使用非线性有限元软件DYNA,分别基于传统有限元与黏聚单元法构造冰层数值模拟模型,模拟平整冰与破冰船相互作用时发生的弯曲断裂以及相互作用的过程。同时,采用经验公式法,用3种不同的经验公式进行冰阻力计算,对影响经验公式法预报结果的参数进行敏感性分析。  结果  研究发现：冰阻力随航速、冰厚度以及弯曲强度的增大呈上升趋势,其中冰厚对冰阻力的影响最大。3种经验公式中,Lindqvist公式的预报结果与船模试验结果更为接近,而Vance和Lewis公式更为保守。传统有限元与黏聚单元法在冰厚较小的情况下,冰阻力预报结果更准确,冰厚较大时误差较大,约25%。在冰厚较小航速较高的情况下,黏聚单元法预报的冰阻力值较传统有限元方法更为准确,与船模试验结果相比精度误差在10%以内。  结论  在实际的冰阻力预报中,可结合经验公式法与数值模拟法,兼顾预报结果的准确性与高效性。     

Generating lane-based intersection maps from crowdsourcing big trace data

Lane-based road information plays a critical role in transportation systems, a lane-based intersection map is the most important component in a detailed road map of the transportation infrastructure. Researchers have developed various algorithms to detect the spatial layout of intersections based on sensor data such as high-definition images/videos, laser point cloud data, and GPS traces, which can recognize intersections and road segments; however, most approaches do not automatically generate Lane-based Intersection Maps (LIMs). The objective of our study is to generate LIMs automatically from crowdsourced big trace data using a multi-hierarchy feature extraction strategy. The LIM automatic generation method proposed in this paper consists of the initial recognition of road intersections, intersection layout detection, and lane-based intersection map-generation. The initial recognition process identifies intersection and non-intersection areas using spatial clustering algorithms based on the similarity of angle and distance. The intersection layout is composed of exit and entry points, obtained by combining trajectory integration algorithms and turn rules at road intersections. The LIM generation step is finally derived from the intersection layout detection results and lane-based road information, based on geometric matching algorithms. The effectiveness of our proposed LIM generation method is demonstrated using crowdsourced vehicle traces. Additional comparisons and analysis are also conducted to confirm recognition results. Experiments show that the proposed method saves time and facilitates LIM refinement from crowdsourced traces more efficiently than methods based on other types of sensor data.     

包海通道西安至安康高速铁路运输需求分析

研究国家高速铁路网包海通道西安至安康高速铁路的运输需求,可为本线主要技术标准、运输组织和建设方案的确定提供决策依据。首先通过旅客运输径路比较分析,确定本线主要承担我国蒙西、陕北、山西、北京、东北地区、关中地区与陕南、西南、广西、海南等地的旅客交流,兼顾陕南重镇安康等与关中城市群、陕北地区的城际客流,其次基于"四阶段法"基本原理,对区域铁路客运量进行分配预测,并按照趋势运量、转移运量、诱增运量进一步分析本线客流密度,最后研究本线客流构成、所在通道的综合交通方式结构,并综合确定本线客车开行方案。