江津中渡长江大桥船桥碰撞力的计算和分析

结合拟建江津中渡长江大桥桥墩船撞力计算,对船舶撞击速度、角度的选取及影响进行了探讨;分别运用国内外现行的规范公式、经验公式及有限元模拟方法,对3 000 t、5 000 t级船舶撞击桥墩的碰撞力进行了计算对比。结果表明:我国现行公路和铁路规范公式计算结果偏小,美国AASHTO规范公式、修正沃辛公式与有限元计算结果基本一致。     

单级主减速器装配新工艺探究

着重介绍利用先进装配工艺方法,有效保证输入轴承预紧力、主被齿啮合间隙、主被齿啮合印迹、差速器齿侧间隙等影响主减速器总成工作性能的参数.     

路堤下涵洞沉降监测及有限元计算

为研究路堤下涵洞的沉降特性,对某路堤下涵洞的沉降进行现场监测,并建立有限元计算模型,得出涵洞断面的沉降分布情况,计算结果与工程实测吻合较好.涵洞基础的弹性模量对涵顶沉降的影响最大,当弹性模屠从40 MPa降至5 MPa时,涵顶沉降值增大4.39倍,其他材料的弹性模量对涵顶沉降不敏感.回填土和地基土的泊松比对涵顶沉降值的影响较大.     

榕江航道整治工程的水沙数值模拟

针对榕江的水沙运动特点,结合工程河段的航道整治工程,建立了适合该区域的二维水沙数学模型,模拟该区域的水沙运动情况,并采用实测资料进行了模型验证,所得计算结果与实测资料比较吻合。证明模型能较好地模拟受潮汐影响河道的水流泥沙运动情况,可为河道的整治提供技术支持。     

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利用元胞自动机,建立了冰雪条件下城市道路单车道和双车道交通流微观模型。针对冰雪条件下驾驶员出于安全考虑降低车速、保持较大车间距的现象,细化了元胞尺寸,引入反映不同冰雪条件的速度因子参数和间距因子参数。通过数值模拟,得出了正常天气和冰雪天气下的车辆速度、密度、流量间的关系曲线,并分析了不同冰雪条件对交通流的影响。研究发现,中雪条件下的车速波动程度及范围最大;基本图显示冰雪条件对于临界密度、最大流量等参数影响较大;冰雪条件下的亚稳回滞现象不明显,未出现换道频率局部最大值。     

分离式路基设计中若干问题的探讨

对分离式路基概念、两幅路之间的间距、设计最小长度、应用范围等方面进行探讨,提出分离式路基在设计时应注意的问题,建议在高等级公路设计中应合理、灵活应用分离式路基。     

基于GML/SVG的空间信息发布技术

介绍了万维网地理信息系统(WebGIS)的发展现状,描述了基于开放性标准的地理标记语言 (GeographyMarkupLanguage,简称GML)和可伸缩的矢量图形(ScalableVectorGraphics,简称SVG)技术,根据各自的特点,给出了一种基于GML/SVG矢量地图Web发布的技术方案,并通过实例验证了其可行性。     

Effect of mass ratio on hydrodynamic response of a flexible cylinder

The effect of the mass ratio on the flow-induced vibration (FIV) of a flexible circular cylinder is experimentally investigated in a towing tank. A Tygon tube with outer and inner diameters of 7.9 mm and 4.8 mm, respectively, was employed for the study. The tube was connected to a carriage and towed from rest to a steady speed up to 1.6 m/s before slowing down to rest again over a distance of 1.6 m in still water. Reynolds number based on the cylinder’s outer diameter was 800–13,000, and the reduced velocity (velocity normalized by the cylinder’s natural frequency and outer diameter) spanned from 2 to 25. When connected, the cylinder was elongated from 420 mm to 460 mm under an axial pre-tension of 11 N. Based on the cylinder’s elongated length, the aspect ratio (ratio of the cylinder’s length to outer diameter) was calculated as 58. Three mass ratios (ratio of the cylinder’s structural mass to displaced fluid mass, m*) of 0.7, 1.0, and 3.4 were determined by filling the cylinder’s interior with air, water, and alloy powder (nickel-chromium-boron matrix alloy), respectively. An optical method was adopted for response measurements. Multi-frequency vibrations were observed in both in-line (IL) and cross-flow (CF) responses; at high Reynolds number, vibration modes up to the 3^rd one were identified in the CF response. The mode transition was found to occur at a lower reduced velocity for the highest tested mass ratio. The vibration amplitude and frequency were quantified and expressed with respect to the reduced velocity. A significant reduced vibration amplitude was found in the IL response with increasing mass ratios, and only initial and upper branches existed in the IL and CF response amplitudes. The normalized response frequencies were revealed to linearly increase with respect to the reduced velocity, and slopes for linear relations were found to be identical for the three cases tested.     

有源干扰对舰载武器系统雷达影响分析

通过电磁波在时域、频域、空域和能量域的相关特性,进行了有源干扰对舰载武器系统雷达影响的分析,给出了清晰的分析流程和简明的分析方法,对进一步研究有源干扰对舰载武器系统雷达影响问题研究,具有一定的参考价值。     

通信干扰目标威胁评估模型研究

对通信干扰目标进行科学威胁评估和排序是对通信目标干扰重要环节,是进行通信干扰资源任务分配的主要依据。TOPSIS方法简单明确,可以非常有效地对通信干扰目标进行威胁评估和排序。为通信干扰目标威胁评估提供了一种有效的、可靠的新途径。