On the Polygonal Wear Evolution of Heavy-Haul Locomotive Wheels due to Wheel/Rail Flexibility and Its Mitigation Measures

Wheel polygonal wear can immensely worsen wheel/rail interactions and vibration performances of the train and track,and ultimately,lead to the shortening of service life of railway components.At present,wheel/rail medium-or high-frequency frictional interactions are perceived as an essential reason of the high-order polygonal wear of railway wheels,which are potentially resulted by the flexible deformations of the train/track system or other external excitations.In this work,the effect of wheel/rail flexibility on polygonal wear evolution of heavy-haul locomotive wheels is explored with aid of the long-term wheel polygonal wear evolution simulations,in which different flexible modeling of the heavy-haul wheel/rail coupled system is implemented.Further,the mitigation measures for the polygonal wear of heavy-haul locomotive wheels are discussed.The results point out that the evolution of polygonal wear of heavy-haul locomotive wheels can be veritably simulated with consideration of the flexible effect of both wheelset and rails.Execution of mixed-line operation of heavy-haul trains and application of multicut wheel re-profiling can effectively reduce the development of wheel polygonal wear.This research can provide a deep-going understanding of polygonal wear evolution mechanism of heavy-haul locomotive wheels and its mitigation measures.

Drag Coefficient of a Non-Convex Polygonal Plate during Free Fall

Waterside creatures or aquatic organisms use a fin or web to generate a thrust force. These fins or webs have a non-convex section, referred to as a non-convex shape. We investigate the drag force acting on a non-convex plate during unsteady motion. We perform the experiment in a water tank during free fall. We fabricate the non-convex plate by cutting isosceles triangles from the side of a convex hexagonal plate. The base angle of the triangle is between 0° to 45°. The base angle is 0 indicates the convex hexagonal thin plate. We estimate the drag coefficient with the force balance acting on the model based on the image analysis technique. The results indicate that increasing the base angle by more than 30° increased the drag coefficient. The drag coefficient during unsteady motion changed with the growth of the vortex behind the model. The vortex has small vortices in the shear layer, which is related to the Kelvin-Helmholtz instabilities.

Differences of polygonal faults related to upper Miocene channels:a case study from the Beijiao sag of Qiongdongnan basin,South China Sea

Deep-water coarse-grained channels are embedded within a polygonal fault tier,and the polygonal faults(PFs)present non-polygonal geometries rather than classic polygonal geometry in plan view.However,PFs present differences when they encounter deep-water(coarse-grained vs.fine-grained)channels with different lithology,which has not been further studied to date.Three-dimensional(3D)seismic data and a drilling well from Beijiao sag of Qiongdongnanbasin,South China Sea were utilized to document the plan view and cross-sectional properties of the PFs and their differences and genetic mechanism were investigated.Results show that,first,PFs can be divided morphologically into channel-segmenting PFs and channel-bounding PFs in plan view.The former virtually cuts or segments the axes of channels in highand low-amplitudes,and the latter nearly parallels the boundaries of the channels.Both are approximately perpendicular to each other.Secondly,channel-bounding PFs that related to low-amplitude channels are much longer than those of high-amplitude ones;channel-segmenting PFs related to low-amplitude channels are slightly longer than the counterparts related to high-amplitude channels.Lastly,the magnitudes(e.g.,heights)of the PFs are proportional to the scales(e.g.,widths and heights)of low-amplitude channels,whereas the magnitudes of the PFs are inversely proportional to the scales of high amplitude channels.Coarse-grained(high amplitude)channels act as a mechanical barrier to the propagation of PFs,whereas fine-grained(low-amplitude)channels are beneficial to the propagation and nucleation of PFs.Additionally,the genetic mechanism of PFs is discussed and reckoned as combined geneses of gravitational spreading and overpressure hydrofracture.The differences of the PFs can be used to reasonably differentiate coarse-grained channels from fine-grained channels.This study provides new insights into understanding the different geometries of the PFs related to coarse-grained and fine-grained channels and their genetic mechanism.

Differences of Polygonal Faults with Irregularly Polygonal Geometries: A Case Study from the Changchang Sag of Qiongdongnan Basin, Northern South China Sea

Polygonal faults(PFs)generally have a classic polygonal geometry in map view.However,under the influence of tectonic faults,diapirs,channels,and slopes,the classic polygonal geometry of PFs is not preserved,demonstrating differences(different characters)in map-view 3D seismic data covering an area of 334km^(2) of the Changchang(CC)sag,are used to document the mapview and cross-sectional characteristics of PFs.These data also help investigate the irregularly polygonal geometries of PFs due to the presence of influence factors,such as transtensional faults,submarine fans,channels,diapirs/gas chimneys,and the basal slope within the lower-middle Miocene strata.Results show that various irregularly polygonal geometries of PFs can be classified into enechelon and arcuate PFs,channel-segmenting and-bounding PFs,radial PFs,and rectangular PFs in map-view.En-echelon and arcuate PFs are induced by transtensional faults and exhibit a unique‘flower’structure in NE-and SE-trending cross-sections in the NW area of the study area.This finding is documented for the first time.Channel-segmenting PFs occur in the(northwest)low-amplitude muddy channel and are inhibited in the(southeast)high-amplitude sandy channel in the SW area.Radial PFs are radially aligned around a gas chimney/diapir containing some high-amplitude anomalies(HAAs)in the middle area.The presence of intrusive sandstones with HAAs along the periphery of the diapirs restricts the occurrence of PFs.Two high-amplitude submarine fans act as a mechanical barrier to the propagation of PFs.Meanwhile,the(moderate)slope in the NE area induces rectangular PFs.Additionally,the geneses of the PFs in the current study are comprehensively discussed.This study adds to our understanding of the differences between PFs with irregularly polygonal geometries.

Radio-Anatomical Study of Anterior Variants of the Polygon of Willis

The anterior system of the polygon of Willis plays an anastomotic role between the carotid territories and communicates with the posterior system. It ensures adequate cerebral blood flow in the event of internal occlusion. Its ability to redistribute blood flow depends on its morphology, the presence and size of the vessels that constitute it and their variants, knowledge of which is essential. The morphology of the carotid system is not constant and a number of variants are well recognized with greater hemodynamic importance. In this context, we undertook this work which aims to seek the anatomical variants of the anterior part of the PW;to determine the diameters of the vessels of the latter and to correlate these results with epidemiological data. We carried out a retrospective, descriptive and analytical study over a period of 4 months at Fann University Hospital, targeting patients who had undergone brain MRI with a 3D TOF sequence whatever the indication. Patients with lesions of cerebrovascular pathologies such as ischemia, hemorrhage, aneurysm, arteriovenous malformations or presenting a limited analysis examination due to the presence of kinetic or other artifact, were not included. Demographic data and anatomical variants were studied as well as the measurements of any continuous arterial segment greater than 0.8 mm in diameter. Those less than 0.8 mm in diameter were considered hypoplastic. The C3 segment of the internal carotid arteries, the A1 segment of the anterior cerebral arteries, the anterior communicating artery, constituted our main measurement sites. The sex ratio was 1.06, the mean age of the patients was 43 years ± 17.9 with extremes of 11 and 85 years. The anterior configuration of the polygon was complete in 57.5% representing 50% of men and 65.5% of women, in 56% of subjects under 40 years old and 58% in subjects over 40 years old. We noted a predominance of type a in 47% of patients followed by type g found in 35% of patients. The morphology of the anterior system of the Willis polygon is a function of its variants, some of which have greater hemodynamic importance than others. Its knowledge is essential for the management of cerebrovascular diseases.

基于轴箱垂向振动加速度的地铁车轮失圆状态诊断方法

首先,建立卷积神经网络、深度置信网络、支持向量机和以一维卷积神经网络全连接层特征为输入的支持向量机模型(1DCNN-SVM),对比上述模型在地铁车轮失圆状态分类识别上的效果;其次,利用代理模型构建轴箱垂向加速度均方根与车速和多边形磨耗幅值之间的映射关系;最后,通过智能优化算法逆向求解幅值,对比不同代理模型和智能优化算法在多边形磨耗幅值识别上的适用性。研究结果表明:1DCNN-SVM模型在正常、低阶多边形、高阶多边形、随机非圆车轮4类典型的车轮不圆度状态分类识别中取得99.82%的准确性,相比另外3种分类方法,其泛化性能和强化学习能力都具有明显的优势。在车轮多边形磨耗幅值识别方面,基于克里金模型(KSM)和粒子群算法(PSO)的波深识别模型具有更好的预测稳定性和时效性。

基于多分辨率-多边形单元建模策略的多材料结构动刚度拓扑优化方法

利用多边形有限单元的高精度求解优势,融合多分辨率拓扑优化方法,实现粗糙位移网格条件下的高分辨率构型设计,由此提出多材料结构动刚度问题的拓扑优化方法。将多边形单元(位移场求解单元)劈分为精细的小单元,构造设计变量与密度变量的重叠网格,形成多分辨率-多边形单元的优化建模策略;以平均动柔度最小化为目标和多材料的体积占比为约束,建立多材料结构的动力学拓扑优化模型,通过HHT-α方法求解结构动响应,采用伴随变量法推导目标函数和约束的灵敏度表达式,利用基于敏度分离技术的ZPR设计变量更新方案构建多区域体积约束问题的优化迭代格式;通过典型数值算例分析优化方法的可行性和动态载荷作用时间对优化结果的影响机制。

硫酸盐对混凝土侵蚀过程的细观数值分析

硫酸盐侵蚀作为混凝土耐久性损伤的一个重要方面,日益受到人们的普遍关注。根据Fick第二定律和化学反应动力方程,建立了细观层面硫酸盐对混凝土侵蚀过程的数值分析方法。以混凝土随机凸多边形骨料模型为基础,利用Matlab程序对有限元软件进行二次开发,建立了基于扩散-化学反应的硫酸盐对混凝土侵蚀过程的细观数值分析方法,并与试验结果进行了对比。结果表明:硫酸盐侵蚀过程细观数值方法得到的模拟结果与试验结果吻合较好,可以有效模拟硫酸盐对混凝土的侵蚀过程;距混凝土表面一定深度范围内,SO_(4)^(2-)浓度随表面SO_(4)^(2-)浓度的提高而增加;砂浆中SO_(4)^(2-)扩散系数是影响混凝土内SO_(4)^(2-)最大侵蚀深度的主要因素;界面过渡区厚度对硫酸盐环境中混凝土损伤的影响较小。

具有独立缓冲结构的PDC—牙轮复合钻头研制

油气勘探开发过程中,难钻地层钻井效率低、钻头寿命短是影响深井、超深井钻井周期和成本的瓶颈问题。钻头工作过程中切削结构轮流与井壁接触而产生的多边形效应是导致钻头不稳定工作、切削齿冲击失效的主要因素。为提高钻头工作稳定性,提出了具有独立缓冲结构的PDC—牙轮复合钻头新结构,并针对四川盆地茅口组Ø311.2 mm井段常规PDC钻头冲击失效严重的问题,设计了3+3+3型(3个主刀翼、3个牙轮以及3个独立缓冲刀翼)的独立缓冲结构复合钻头,开展了全尺寸钻头室内钻进对比实验,并在川渝页岩气区块茅口组—栖霞组地层进行了实钻应用。研究结果表明:①独立缓冲结构复合钻头在常规复合钻头的牙轮切削结构和固定切削结构之间的空隙部位增设独立缓冲刀翼,有效缓解了多边形效应,对PDC齿形成很好的缓冲保护,同时分担了过大的钻压,限制了切削齿吃入深度,进而防止了钻头产生粘滑振动;②独立缓冲结构复合钻头钻压和扭矩波动小,扭矩为PDC钻头的1/5;③独立缓冲结构复合钻头取得了单只钻头进尺170 m的记录,比邻井同层位单只PDC钻头最高进尺提高了73.5%。结论认为,独立缓冲刀翼对提高钻头的稳定性起到了关键作用,不仅提高了钻头寿命,而且有效提高了复杂难钻地层及复杂结构井的综合钻井时效,有效降低了油气勘探开发成本。

基于轨迹线改进的临界多边形算法

在异形件的下料排样问题中,最为困难的就是求解裁片在板料中的位置以保证材料较高的利用率,算法复杂度随着料片数量和料片轮廓复杂度的增加迅速上升。临界多边形算法是计算异形件之间靠接位置和重叠关系的一种基础性几何工具,临界多边形算法的性能与下料排样算法效率密切相关。本文在基于轨迹线的求解临界多边形算法基础上,提出一种求解临界多边形(NFP)的改进算法。该算法有效地将移动碰撞算法和轨迹线算法相结合,充分发挥两类算法各自的优点,提高了临界多边形求解的计算速度。仿真实例验证了改进方法的正确性和有效性。

泰森多边形多孔结构髋臼杯初始稳定性研究

目的 分析泰森多边形多孔结构髋臼杯与实体髋臼杯的初始稳定性差异,探究泰森多边形结构多孔层对髋臼杯初始稳定性的影响及其在预防松动脱位方面的作用。方法 通过Grasshopper设计孔隙率分别为60%、70%的泰森多边形多孔结构支架,利用选区激光熔化技术(selective laser melting, SLM)制备实体髋臼杯与孔隙率为60%、70%多孔髋臼杯样件,在相同条件的聚氨酯块模型中进行杠杆试验,分析对比3组样件的最大撬出力矩、偏转角度、界面刚度。结果 在压入力无明显差异的情况下,孔隙率为60%、70%多孔髋臼杯的最大撬出力矩分别比实体髋臼杯高278.82%、320.56%,偏转角度比实体髋臼杯高194.04%、269.23%,界面刚度比实体髋臼杯高18.58%、7.88%。杠杆试验完成后,多孔髋臼杯所用的聚氨酯块半球腔内出现明显磨损。结论 泰森多边形多孔结构髋臼杯的初始稳定性指标均高于实体髋臼杯,说明泰森多边形结构多孔层能提高髋臼杯的初始稳定性。研究结果能够为髋臼假体的设计与选型提供一定参考。

防空作战中多边形责任区预警机空域配置方法

针对防空作战中不规则多边形责任区预警机空域配置问题,基于预警机巡逻航线最短直飞距离和最小转弯直径所形成的实时探测区,通过寻优算法确定预警机责任子区和相应的预警机巡逻可用空域,再基于预警机稳定覆盖度评估准则,对其空域配置进一步寻优,得到预警机空域配置优化方案。通过算例仿真验证了此种方法在不规则多边形责任区中规划预警机空域配置的可行性和提升作战效能的有效性,其方法具有较强的实用价值和军事价值。

一类交错链环的棍棒指标估计

纽结与链环的分类及相关性质是三维流形方向的重要研究内容.纽结和链环的各种代数和几何不变量是纽结与链环合痕分类的实用工具,这些不变量主要包括纽结与链环的琼斯多项式、亚历山大多项式、交叉指标、棍棒指标等.纽结与链环的棍棒指标是从三维流形组合拓扑的角度出发研究纽结和链环合痕分类的不变量.纽结与链环的缠绕分解是研究纽结和链环性质与合痕分类的重要方法.从一类交错链环对应的非代数投影图的缠绕分解出发,对不同位置的整数缠绕采用不同的分段线性构造方式,并通过调整局部位置的整数缠绕对应多边形表示出口边的角度,减少构造整数缠绕对应多边形表示所需的边数,给出一类交错链环的棍棒指标估计.

车轮多边形磨耗对地铁列车蠕滑特性的影响分析

为研究车轮多边形磨耗对轮轨接触蠕滑特性的影响,依据多体动力学理论和滚动接触理论,建立基于地铁列车参数的多体动力学模型,并计算多工况下车轮踏面磨耗指数,分析车轮多边形阶数和幅值变化对轮轨力、蠕滑率和蠕滑力等特性的影响,结果表明:蠕滑率以及蠕滑力会随车轮多边形阶数和幅值的上升而增大;车轮踏面磨耗随地铁列车运行里程的增加而逐步增大。使用轮轨垂向力指标,根据车速小于160 km/h,轮轨力应不大于200 kN的标准,确定地铁列车80 km/h运行速度下3~23阶多边形幅值安全限值,结果表明多边形幅值安全限值随阶数增加呈下降趋势。

基于三维重建外点剔除的船舶航迹自适应修正

为了保证船舶的安全性,通过三维重建外点剔除进行船舶航迹自适应修正。采用均值限差法对船舶三维点云数据进行滤波处理,通过变窗口方差比值方法优化均值限差法,提升船舶三维点云滤波精度。针对滤波处理后的船舶三维点云数据,结合八叉树自适应网格对船舶进行三维重建,更准确地拟合船舶的表面形状。由此,在屏幕上投影八叉树自适应网格生成投影多边形,检测其与用户确定的矩形包围盒间的相交性,定义与矩形包围盒不相交的八叉树自适应网格内的点为外点,并将其剔除,可以更准确地计算船舶航行,完成船舶航迹自适应修正。实验结果表明,所提方法的点云滤波总误差控制在1.5%以内,可有效抑制海面杂波等因素造成的外点影响,且规划的航线与原定航线一致性较高,可以保证船舶的运行安全。

含界面过渡区随机分布多边形骨料沙漠砂混凝土高温后抗压强度研究

为研究试件尺寸、界面过渡区(ITZ)厚度及强度、沙漠砂替代率(DSRR)对沙漠砂混凝土(DSC)经历高温后抗压强度的影响,将DSC看作三相复合材料,建立含ITZ随机分布多边形骨料有限元模型,利用ANSYS对高温后DSC单轴受压破坏过程进行数值模拟。结果表明:模拟结果与试验结果误差在-2.59%~3.13%,吻合良好。高温后DSC抗压强度随试件尺寸增大而减小,强度下降范围为1.44%~4.13%;抗压强度随ITZ厚度增加呈逐渐减小趋势;随着ITZ强度增加,抗压强度基本呈线性增大趋势;抗压强度在DSRR为40%时最优,研究结果可为DSC工程应用提供理论依据。

多边形沙地挖坑植树机设计与转动性能分析

为了改善土地荒漠化的问题,降低植树造林对人力的依赖性,提高造林的效率和质量,设计一台用于沙地的多边形挖坑植树机。基于三维建模软件UG软件设计出一种适用于沙地的多边形挖坑植树机的几何模型,通过动力学分析推导出拉动旋转框架所需的拉力,并导入动力学仿真软件ADAMS进行了动力学仿真分析,得到旋转框架转动过程中质心位移曲线、绕转动轴力矩变化曲线和质心速度变化曲线,从而为旋转框架转动过程提供了分析的依据并验证方案的可行性。

一种基于径向基隐式曲面的地质三维建模方法

针对目前基于钻孔数据生成地质三维模型过程繁琐、算法复杂、中间数据庞大的弊端,本文使用钻孔点和径向基隐函数模型描述地层曲面,以多边形标量场提取曲面函数模型的等势面生成地质曲面进行可视化;再提取曲面的边框,根据网格大小长度提取边框的转折点数据;根据上下相邻两个地层曲面的边框转折点,绘制侧立面;合并侧立面与上下相邻两地质层曲面,生成地质三维模型。并使用郑州市高新区地质钻孔数据作为数据源进行实验,快速完整地生成了研究区的地质体三维模型。

SUBDIVISION建模在室内有机形态的应用研究

通过探索Subdivision建模技术在室内设计中的潜力,提高室内设计有机形态的吸引力和竞争力,并且有效提高设计师在有机形态设计中的效率。通过分析Subdivision建模原理,介绍其在室内运用的可能性、高效性、调节性、仿生性的特点。对其Subdivision建模在室内设计应用中的有机拓扑形态、空间界面软化、泰森多边形应用、渐消面的运用等几点优势展开讨论。结合乐嘉伦敦展厅和BarinSkiResort、Batwings案例,阐述其非线性美学和有机形态,解读其设计特点。进一步分析Subdivision建模的有机形态表达优势与局限性,探讨Subdivision建模在室内设计中的有机结构建模的可行性。探析出Subdivision建模技术能够更好设计具有非线性美学的有机形态,更有助于创造出独特的艺术形式和空间感受。为相关室内空间有机形态的设计提供了创新的设计思路。

浸入运动边界-格子Boltzmann方法4种固含率计算方法对比研究

为了达到流固耦合,格子Boltzmann方法(LBM)可采用浸入运动边界法(IMB)实现移动颗粒边界上的无滑移条件.该耦合方式(IMB-LBM)中固含率计算方法对流固耦合计算精度和效率有影响.对常用的固含率4种计算方法,即蒙特卡洛法(MCM)、单元分解法(UDM)、近似多边形法(APM)和闭合边界法(CBM),分别阐述其具体算法,对比了它们的计算精度和计算效率;最后通过圆盘颗粒非连续变形分析方法(DDDA)与IMB-LBM耦合模型下的一个多颗粒沉降流固耦合算例,对比分析了它们在流固耦合计算过程中的耗时.结果表明:1)CBM无误差,MCM和UDM在随机点数取1000,子单元数取100时误差稳定在1%以下,APM在颗粒直径大于格子长度10倍时,误差小于0.44%;2)MCM和UDM的计算精度及耗时分别与随机点数和子单元数相关,它们的计算耗时大于APM和CBM;3)计算效率上,APM>CBM>UDM>MCM,其中CBM计算耗时略微大于APM,APM和UDM计算耗时分别比MCM少2个和1个数量级.该结果可为IMB-LBM耦合模型中固含率计算方法优选提供借鉴.