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采用电磁场积分方程(EFIE、HFIE)结合矩量法分析了介质球、介质圆柱、介质立方体的电磁散射问题。介质目标表面的剖分用三角形面元,面元上的电磁流分布用子域基函数表示,用伽略金法将电磁场积分方程转化为矩阵方程,并求解矩阵获得电磁流系数。 相似文献
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将小波分析与矩量法结合起来,分析求解了方环天线的电流分布。用小波基代替矩量法中的基函数和权函数,使矩量法中与算子相对应的矩阵变成大量元素为零的稀疏矩阵,从而大大减少了计算量。计算结果与用矩量法计算的结果吻合较好。 相似文献
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介绍了有关散乱数据拟合研究中的径向基函数方法,我们把区域分解法与径向基函数法结合给出了散乱数据拟合的异步并行算法.进而证明了此算法的收敛性。 相似文献
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风致气动噪声作为邮轮阳台区域的主要噪声源,极大地影响着乘坐舒适性。现有计算水平难以对邮轮全船的风致气动噪声进行预报,且因邮轮阳台区域前方遮蔽物较多,局部流场计算时的边界条件也很复杂。基于子域赋值法,对邮轮局部阳台区域进行气动噪声预报的可行性研究。以有棱柱遮挡的圆柱为研究对象,以全场流场预报得到的流场以及声场结果为基准,评估了在遮蔽复杂环境下采用子域赋值法进行局部流场以及气动噪声预报的准确性。采用该方法对邮轮正向20 m/s迎风时中部典型阳台区域的气动噪声进行预报,得到该阳台区域的气动声压分布情况。结果表明,在该阳台区域人站立高度处,噪声峰值约为63 dB(A),峰值频率为1 250 Hz,因此需对相应的阳台房进行隔声处理。 相似文献
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在Dr.Wang的模糊逻辑系统基础上,提出了改进的α-模糊基函数系统,使其能充分表征语言信息和数据信息及其反馈作用。接着依据MOLS算法,提出了α-模糊基函数系统的确定算法。仿真结果表明,笔者提出的理论和方法是有效的。 相似文献
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径向基神经网络的构造理论 总被引:2,自引:0,他引:2
通过对径向基神经网络的研究,提出了径向基经网络的构造性理论及其构造算法,在给定函数及其允许误差的条件下,运用本算法能够构造几乎最少隐节点数的径向基神经网络。 相似文献
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WANGXiao-tian QINZai-bai GAOLing-zhi LIANGXue-xian 《船舶与海洋工程学报》2004,3(2):12-16
In the previous research, the effect of the frame torsion on the local stability of a ring-stiffened cylindrical shell, which was proved to be significant, was usually omitted. In this paper this effect under the action of static water pressure is studied. The frame torsional strain energy is calculated by consulting the method used in the research on the stability of a stiffened rectangular plate. With this item of energy being introduced into the total potential energy of the structure, a new stability formula for calculating the critical pressure for the local buckling of the ring-stiffened cylindrical shell is obtained by Ritz method. This new formula can be regarded as a revision of the famous Mises‘ formula. The calculation of the example shows that the critical pressure given by this formula is closer to the model test data than that given by Mises‘ formula. 相似文献
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本文将Ritz矢量和逐点放松法应用于固定界面模态综合法,其一是用固定界面Ritz矢量替代子结构的固定界面模态,其二是在形成缩聚刚度阵和质量阵时以逐点放松消去法替代矩阵求逆的计算。实例计算证明,两个替代方案均能节省较多的计算机时。 相似文献
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The CO_2 emission reduction policy of the International Maritime Organization(IMO) recommends that the operation of ships,managed by maritime transport companies, should be energy-efficient. An evaluation method that can determine how successfully a ship implements the energy efficiency plan is proposed in this study. To develop this method, the measures required for energy-efficient ship operations according to the Ship Energy Efficiency Management Plan(SEEMP) operational guidelines were selected. The weights of the selected measures, which indicate how they contribute to the energy-efficient operation of a ship, were derived using a survey based on the analytic hierarchy process(AHP) method. Consequently, using these measures and their weights, a new evaluation method was proposed. This evaluation method was applied to shipping companies in South Korea, and their ship operation energy efficiency indices were derived and compared. This evaluation method will be useful to the government and shipping companies in assessing the energy efficiency of ship operations. 相似文献
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统计能量分析方法能够有效预示舰船和车辆等结构的高频振动及噪声。本文通过建立两子结构耦合模型,利用差分法研究了瞬态统计能量分析中参数误差对子结构响应能量的影响,同时给出了参数误差与所导致能量误差的关系函数。结果表明:对于外载荷直接激励的子结构,内损耗因子和耦合损耗因子的误差都会导致被预示总能量的减小。对于外载荷间接激励的子结构,内损耗因子的误差会导致峰值能量的减小,而耦合损耗因子的误差会导致峰值能量的增加。本文内容对改进动力学系统数值模型以及提高结构振动和噪声预示精度有一定的帮助。 相似文献
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船舶复杂轴系扭转振动建模及动力学分析 总被引:1,自引:0,他引:1
针对船舶复杂轴系结构,提出一种基于能量法的轴系扭转振动建模及动力学分析方法。该方法对船舶复杂轴系中的典型结构进行统一能量化描述,如联轴器、齿轮、负载等,并结合弹性轴的能量函数构建轴系结构的拉格朗日能量泛函;然后,利用最小二乘法和广义变分法,对轴系角位移展开项系数进行求解,从而建立适用于船舶复杂轴系结构的扭转动力学模型。通过与有限元方法计算结果相比较来验证该建模方法的准确性,并利用该方法分析连接刚度和负载转动惯量对整体轴系扭振特性的影响,以期为船舶复杂轴系设计提供一定参考。 相似文献
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《船舶与海洋工程学报》2015,(2)
Energy optimization is one of the key problems for ship roll reduction systems in the last decade. According to the nonlinear characteristics of ship motion, the four degrees of freedom nonlinear model of Fin/Rudder roll stabilization can be established. This paper analyzes energy consumption caused by overcoming the resistance and the yaw, which is added to the fin/rudder roll stabilization system as new performance index. In order to achieve the purpose of the roll reduction, ship course keeping and energy optimization, the self-tuning PID controller based on the multi-objective genetic algorithm(MOGA) method is used to optimize performance index. In addition, random weight coefficient is adopted to build a multi-objective genetic algorithm optimization model. The objective function is improved so that the objective function can be normalized to a constant level. Simulation results showed that the control method based on MOGA, compared with the traditional control method, not only improves the efficiency of roll stabilization and yaw control precision, but also optimizes the energy of the system. The proposed methodology can get a better performance at different sea states. 相似文献
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对规则波中顶浪并行航行的两船模,基于频域移动脉动源格林函数建立了有效表达池壁效应的三维数学模型,该模型采用分布源积分方法求解近距航行两船模的波浪作用力和运动响应,并利用镜像原理将水池格林函数表示为开阔水域的格林函数和由镜像点源组成的无穷级数.分析移动脉动源格林函数的远场传播模态及其特性可知,当τ>0.272(τ为斯特劳哈尔数)时各传播波模态均不在点源的上游出现,故此时点源波系的影响范围可由环形—扇形波的半楔角确定,在此基础上计及船模辐射—绕射波的池壁反射作用对自身和另一船模的干扰,依据船型要素、水池宽度和两船相对位置,采用六个几何临界半楔角表征船体的辐射—绕射波,提出了并行航行两船模的池壁效应判别方法.数值研究表明:不同镜像次数下水池格林函数的数值差异主要体现在距船艏较远处,在兼顾计算精度与效率的原则下可选取有限项级数的水池格林函数作为积分内核,而池壁效应对近距航行两船运动响应的影响主要体现在长波区. 相似文献