S-175集装箱船舶波浪载荷的船模试验与线性切片理论计算的比较

本文就日本S-175集装箱船舶的波浪载荷进行了船模试验与线性切片理论计算的比较,发现线性切片理论对于波浪载荷沿船长的纵向分布以及中拱与中垂的不同分量都与试验值存在着相当大的差异,仅纵向运动较为满意;揭示了对于在高浪级下快速舰船的波浪载荷,特别是砰击载荷应致力于开展非线性理论和试验研究。     

Slow drift damping force acting on a horizontal cylinder

The hydrodynamic forces acting on a circular cylinder and a rectangular cylinder undergoing slow drift oscillation in regular waves were investigated experimentally and numerically. Forced oscillation tests with low frequency and large amplitude in regular waves and forced two-harmonic oscillation with combined low and high frequencies were carried out in the experimental study. In the numerical study a finite-difference method was used to simulate viscous flow around a two-dimensional oscillating cylinder. The results of experiments showed that a horizontal rectangular cylinder oscillating slowly in waves has much higher damping coefficients than one oscillating in two-harmonic mode, while the numerical study indicated that such differences in the damping coefficient arise partly from the different effects of one-direction harmonic flow and rotating flow on the vortex shedding caused by the slow drift oscillation.     

蛇形造波机性能测试

对蛇形造波机的机械性能和造波质量进行了测试。所有指标均满足试验要求。规则波最大波高达35cm。多方向不规则波的有效范围达到理论长度。     

Effects of wave directionality and choice of wave spectrum on the extreme response of a deep water jacket

Wave-induced load effects in an idealized deep water jacket are considered. The structure is selected more to examine the worst effects of wave-induced uncertainties than to represent a realistic North Sea installation. The largest natural period is about 5 9 s and the structural response is significantly affected by dynamics. The structural system is linearized and response extremes are predicted by means of a stochastic, dynamic long term response analysis. A realistic modelling of ocean waves for long term response calculations is outlined. Various possibilities concerning the choice of wave spectrum are included and the corresponding effects on the predicted extremes are demonstrated. A sensitivity study is carried out both for the quasi-static response and for the resulting dynamic response. Finally, the effects of accounting for wave directionality are indicated. This includes both the introduction of a varying main wave direction and the modelling of the shortcrestedness for a given sea state.     

交流传动电力机车网侧谐波分析与对策

就交流传动电力机车网侧谐波进行了较为详细的分析,根据不同系统的特点及其影响提出应采取的措施和建议,为电力机车总体及其主电路重大部件的设计,以及供电系统相关参数的选择,提供了参考。     

用tent函数计算兴波阻力及优化船型问题

本文用理论方法计算了兴波阻力和改良船型的型值。理论计算可分下列两种情况: (1)对基本船型的水线迭加曲线薄船函数以计算其对应的改良船型。 (2)对基本船型的曲表面迭加曲面薄船函数以计算其对应的改良船型。 本文利用C.C.Hsiung提出的用tent函数方法计算兴波阻力。用SUMT混合罚因子优化技术计算改良船型的型值。 本文以y=(1-x~2)(1-z~4)数学船型和Series 60实用船型为基本船型,用tent函数方法对它们进行了兴波阻力计算,并且与其它兴波阻力计算方法进行了比较。本文还以上述两种船型为基本船型进行了改良船型的计算,并且得到了与它们相应的理论改良船型。     

On nonlinear ship waves and wave resistance calculations

A finite difference method based on the Euler equations is developed for computing ship waves and wave resistances. Time marching is carried out using a time-splitting fractional-step method. The second-order central difference is used to discretize the spatial differentials, while the convection terms are discretized by the QUICK scheme. A body- and free-surface-fitted grid system with a cell-centered stencil is used. A Poisson equation for the pressure increment at each time step is solved to enforce mass conservation. The method is validated by comparing the numerical results with the experimental data for a Wigley parabolic hull. The characteristics of ship waves, such as the wave profile along the hull, the wave pattern on the free surface, the pressure distribution on the hull surface, and the wave-making resistance are reasonably predicted. The calculated results are in good agreement with the experimental data. Received for publication on Oct. 13, 1998; accepted on Jan. 20, 1999     

选择性波峰焊在LED车灯模组生产中的运用

主要阐述汽车用LED模组的组装生产工艺,尤其是针对通孔连接器与SMT电子元器件同时需要焊接的模组,采用选择性波峰焊工艺能够提高焊接品质,降低品质风险。同时对完整的选择性波峰焊焊接工艺流程进行说明,对工艺参数设定进行重点分析和研究。本文也对焊接原理和实际操作两方面进行阐述,并例举了选择性波峰焊的工艺注意事项和对常见问题的分析。     

消除高速公路运动波的可变限速控制方法

运动波是高速公路一种常见的交通拥堵,可通过可变限速控制有效消除。近年来,研究中提出了大量消除高速公路运动波的可变限速控制方法,却鲜有方法成功落地应用。可变限速控制方法的成功应用需满足3个基本条件,即模型预测的准确性,优化求解的实时性,以及控制方案的安全性,而当前研究中的方法难以同时满足上述基本条件。因此,为提高高速公路交通效率,保障高速公路交通安全,提出了消除高速公路运动波的可变限速优化控制方法。构建了模拟运动波传播的离散一阶交通流模型,解析了可变限速控制对交通效率及安全的影响机理,建立了提升交通效率、保障交通安全的可变限速优化控制方法。利用数值仿真模拟,测试了轻微拥堵与严重拥堵2种不同场景下限速控制方法的控制效果,评估了控制方法在提升交通效率和安全方面的表现,对比了所提方法与文献经典方法在控制效果上的优劣。结果表明：可变限速优化控制方法在2种场景下降低总行程时间分别为10.1%和10.6%,降低事故风险指标TET分别为72.6%和73.1%,降低事故风险指标TIT分别为92.4%和82.9%。与文献方法相比,在预测模型准确性以及对交通流效率与安全的改善方面均有提升,其中在严重拥堵测试场景下,效果提升更为显著。     

面向协调路径集与双环结构的区域绿波控制模型

考虑到区域内交叉口之间的方向性协调控制需求,以协调路径集作为区域绿波控制对象,针对双环相位结构建立一种区域绿波协调控制模型。通过对协调路径链、协调路径进行特征表述,结合协调路径的相交情况,分析在进行区域绿波协调控制设计时,不同类型的交叉口协调相位时间基点约束条件;在初选协调路径集的基础上,通过分析公共信号周期、相位时间、相位结构、相位差等优化变量之间的约束条件,以所有满足协调控制设计的协调路径总流量最大为优化目标,建立面向协调路径集与双环结构的区域绿波控制模型,实现对区域绿波协调控制参数的综合优化。模型通过引入协调路径决策变量以及设置交叉口协调相位基点最大允许偏移时间,保证通过区域协调路径集再优选后,纳入最终协调路径集的各协调路径上下游交叉口的协调相位基点受到最大允许偏移时间约束,以获得理想的绿波协调控制效果。算例仿真试验结果表明：与Synchro软件的单点优化和区域协调信号配时设计方案相比,所提模型方案的协调路径集平均延误时间分别减少了35.5%和18.1%,平均停车次数分别减少了74.1%和63.8%,所提模型方案的整个路网平均停车次数分别减少了38.9%和25.1%,可见所提模型能够最大限度地保证区域内协调路径集的绿波协调控制效果,在减少区域停车次数方面效果显著。