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Using locally given vertical velocity data around a wing, an inverse formulation is presented to solve a lifting problem.
The inverse problem is expressed by a Fredholm integral equation of the first kind. In this paper, the kernel of the integral
equation gives a Hilbert–Schmidt integral operator, and therefore the occurrence of ill-posedness in the sense of stability
cannot be avoided in a normal topology. This difficulty is solved by using the regularization method for ill-posed problems.
A composition mapping is introduced so that local velocity data can be available for this inverse problem. In this paper,
the ill-posed inverse problem of a wing is studied using the Landweber–Friedman's regularization method within the framework
of linear potential theory. A numerical example demonstrates that only with locally given velocity data is the regularization
method accurate and suitable for the present physical problem of an inverse mathematical formulation. Therefore, the lifting
problem can be solved by using a locally given fluid velocity instead of a wing geometry.
Received: April 13, 2000 / Accepted: April 20, 2000 相似文献
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船舶碰撞海冰引起的冰载荷分布是十分复杂的。文章选取Thikhonov正则化这一反向方法,根据极地科考补给船S.A Agulhas II号于2013-2014年间南极航行时实测的数据,分析得到了船体艉肩部的冰载荷。通过应用三种独立的冰载荷离散方式来模拟海冰的自然特性,在有限元中得到模型的影响矩阵,并应用Matlab对Thikhonov正则化方程进行了优化。研究结果表明,反向方法可以克服数据处理过程中的不适定性,并计算得到船体冰载荷。 相似文献
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Taek S. Jang Hang S. Choi Takeshi Kinoshita 《Journal of Marine Science and Technology》2000,5(4):181-188
This paper illustrates how to estimate a wave source generating a wave system, including local waves, with the assumption
of linear dispersive waves of two dimensions. The estimation of wave source is realized by using an inverse problem. Unfortunately,
the inverse problem is ill-posed in the sense of stability, since the wave source information included in local waves diminishes
as the distance from the wave source increases. In the area of applied mathematics, there are well-developed methods to tackle
ill-posed problems, which are called regularizations. In this paper, three different regularizations which are well known
in applied mathematics are introduced and investigated to learn whether they are applicable to the present problem of the
estimation of wave source. From the numerical experiments, it is shown that the estimation is realized by the regularizations
introduced in this study, so that they can be applied to the determination of a wave source generating a wave system including
local waves.
Received: June 6, 2000 / Accepted: February 7, 2001 相似文献
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Taek S. Jang Hang S. Choi Takeshi Kinoshita 《Journal of Marine Science and Technology》2000,5(3):107-111
For a given velocity distribution around a hydrofoil, the inverse problem of the hydrofoil is studied. The inverse problem
is formulated by representing the hydrofoil in terms of vortices within the framework of linear potential theory. From the
mathematical formulation, it is known that the inverse problem turns out to be ill-posed in the usual topology. In this paper,
iterative and noniterative regularizations are applied to solve the problem and to find their suitability for the two-dimensional
inverse hydrofoil problem. Numerical experiments demonstrate that the regularization methods are accurate and suitable for
the inverse mathematical formulation for a given velocity distribution around a hydrofoil.
Received: June 6, 2000 / Accepted: December 8, 2000 相似文献
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基于扩展有限元法和改进的人工蜂群智能优化算法,建立了检测和量化结构中多个内部缺陷的反演分析模型。反演分析模型中,由水平集函数来表征每个缺陷的位置及尺寸,采用精英加引导策略的人工蜂群搜索方程进行全局搜索,直到达到收敛为止;提出以人工蜂群对不同数目的缺陷参数样本进行贪婪选择,无需预先知道结构内部所含的缺陷数目,迭代过程中缺陷数目可以智能改变。该模型避免了反演过程中网格重划分问题,有效地减少了迭代的计算成本。通过若干算例的分析表明:在结构内部所含缺陷数目未知情况下,建立的反演分析模型能够快速准确地识别并确认出结构内部存在的缺陷数目及其相应的位置和大小。 相似文献
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《Marine Structures》2002,15(1):35-56
The axiomatic design approach proposed by N.P. Suh consists of the Independence Axiom and the Information Axiom. The Independence Axiom assists a designer in generating good design alternatives by considering the relationships between the functions and the physical product using a hierarchical mapping procedure. The Information Axiom, which is related to the probability of achieving the given functional requirements, can be used as a criterion for the selection of the best solution among the proposed alternatives in the conceptual or preliminary design stage.In the early stages of marine design, especially ship design, there exists a lot of uncertainty because of the size and complexity of a marine vehicle. This uncertainty often leads to a probabilistic approach rather than a deterministic approach. Ship designs are often routine, requiring small modifications of an existing, successful design. The availability of axiomatic design in this marine design field has been investigated through four examples: a conceptual thruster design, a foil-strut optimization problem, a main engine selection problem, and a barge design problem. By these examples, the possibility of the application of Design Axioms in marine design has been illustrated. 相似文献
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船舶机械振动源激励力的间接估计工程方法 总被引:1,自引:0,他引:1
船舶机械设备输出到船体上的激励力对船舶结构振动预报有着重要意义,文章讨论了两种间接估算激励力的方法,目的是希望在工程现场应用这些工程方法取代激励力的直接测量.对刚性安装的机器推荐采用最小二乘方法,该方法是基于支撑结构的加速度导纳特性进行估算.对弹性安装的机器而言,推荐采用基于隔振器阻抗特性的激励力间接估算方法.力的估算是逆问题,文中采用奇异值分解技术来处理会遇到的病态问题,从而尽量降低估算误差.文中还对估算的准确度、估算质量评价等进行了讨论.条件数的倒数在最小二乘法响应点的选取时可作为优选的先验判据,归一化残差可作为估算质量的后验判据.实验证明了间接估算方法是确定船舶机械激励力的恰当选择,实验结果的最小二乘法相对误差为3分贝.测试中的信噪比被认为在力估算过程中有重要影响,低信噪比很可能是实际测试时的首要误差来源.该文也可用于指导船舶振动源特性描述的研究. 相似文献
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为有效解决现有磁性定位方法定位精度不高的问题,提出了基于磁偶极子阵列模型的磁定位方法.为求解模型参数,根据磁场测量数据建立了定位参数反演模型.针对实际舰船磁性检测中所得磁场信息的局部性而引起反演模型病态不适定问题,应用Tikhonov正则化方法优化求解模型参数.船模实验证明,该方法对船模进行定位计算,定位精度高,结果稳... 相似文献
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This paper presents an algorithm for the frequency domain solution of dynamic linear “inverse” problems, that is for the processing of measurement data (strain, acceleration etc.) acquired on a mechanical structure, in order to estimate the loads acting on the structure and its corresponding response. The problem is formulated as a constrained (force equilibrium) optimization (small deviations from measurements, small loads) problem, which is transformed into an unconstrained problem, then into differential equations. The algorithm is applied to the estimation of hydrodynamic forces induced by the shedding of vortices from an offshore oil riser. 相似文献
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船舶舱室布局所涉的评价指标通常具有不确定性,诸如环境载荷等参数通常以不确定性的随机变量形式参与计算,且其概率分布的期望及方差等指标往往也是不确定的。本文采用矩不确定分布鲁棒优化方法,解决含矩不确定参数的船舶舱室布局min-max优化问题。将各舱室的全局位置参数、相对位置参数和质量分布参数加权整合为目标函数,建立全船范围内的舱室布局DRO-MU优化模型,采用拉格朗日对偶原理将其转为确定的半定规划问题以便求解。算例验证了本文方法的合理性与优越性,该方法针对性地用于解决含矩不确定参数的船舶舱室布局问题具有鲜明特点。 相似文献
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采用单传感器的传统船舶电气参数测量方法存在很多缺陷,会受到传感器的测量噪声和电网中的电磁干扰等影响,从而影响参数测量的精度和测量结果的稳定性。为此,应用状态估计技术和多传感器数据融合理论,提出了一种新的船舶电气参数测量方法。首先建立电压和电流的状态模型,将其连续的动态方程离散化,用于数字信号处理器(DSP)中。然后采用卡尔曼滤波和无反馈分布式融合来对离散化后的采样数据进行融合,从而得到全局数据融合的最优估计。最后,经过一个周期的采集数据估计值进行有效值计算,在液晶屏中显示出来。与单个传感器的检测方法相比,该检测方法具有更高的精度和更好的稳定性。仿真结果和实验测试结果都证明了本检测方法的有效性和优越性。 相似文献
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This paper deals with a realistic multi-period liner ship fleet planning problem by incorporating stochastic dependency of the random and period-dependent container shipment demand. This problem is formulated as a multi-period stochastic programming model with a sequence of interrelated two-stage stochastic programming (2SSP) problems characterized ship fleet planning in each single period. A solution method integrating dual decomposition and Lagrangian relaxation method is designed for solving the developed model. Numerical experiments are carried out to assess applicability and performance of the proposed model and solution algorithm. The results further demonstrate importance of stochastic dependence of the uncertain container shipment demand. 相似文献
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目前,多相流技术已经渗透到工作生产的各个领域,多相流参数的测量受到普遍关注。多相流参数的测量方法种类繁多,其中电容法的研究倍受青睐。本文对电容法在多相流参数测量领域的研究进展进行了较为详细的介绍,对其发展中遇到的问题进行了阐述,并对电容法的发展前景进行了展望。 相似文献
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In this paper, we present a two-stage optimization model for the machinery system selection problem. The objective is to minimize total cost, while aggregated power requirement and emission regulations are constraining the problem. Future fuel prices are considered to be uncertain. From a set of alternatives, the machinery configuration providing the lowest total cost is found. Also design flexibility in terms of future reconfiguration possibilities is taken into account. The machinery selection for a 2000 TEU container vessel is used as an illustrative case. Five initial machinery concepts are considered: diesel machinery, diesel machinery with a scrubber system, dual fuel (DF) machinery, pure gas engines, and a DF ready machinery. There is also a set of reconfiguration possibilities available for each alternative. From solving the case study, DF machinery is found optimal, while pure gas machinery is close to equally good. By solving the problem with deterministic fuel prices, the value of flexibility is not properly accounted for, resulting in an unreasonably high total cost for the flexible machinery alternatives. This demonstrates the need for a decision support approach that explicitly handles future uncertainty, as the two-stage stochastic model presented in this paper does. 相似文献
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提出求解确定性联合补充库存问题的新方法——EXCEL规划求解法:通过数学运算将非线性混合整数规划模型转化为整数线性规划模型,然后在EXCEL中通过“规划求解”工具求最优解.通过算例验证,结果表明该方法不但能有效解决此类问题,而且更简单、更直观、更实用. 相似文献