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Zhaoqiang Bi Jian Li Zheng-She Liu 《IEEE transactions on aerospace and electronic systems》1999,35(1):267-281
Super resolution synthetic aperture radar (SAR) image formation via sophisticated parametric spectral estimation algorithms is considered. Parametric spectral estimation methods are devised based on parametric data models and are used to estimate the model parameters. Since SAR images rather than model parameters are often used in SAR applications, we use the parameter estimates obtained with the parametric methods to simulate data matrices of large dimensions and then use the fast Fourier transform (FFT) methods on them to generate SAR images with super resolution. Experimental examples using the MSTAR and Environmental Research Institute of Michigan (ERIM) data illustrate that robust spectral estimation algorithms can generate SAR images of higher resolution than the conventional FFT methods and enhance the dominant target features 相似文献
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胡微 《北华航天工业学院学报》2012,22(3):24-26
本文针对我国有限责任公司股东优先购买权在实践中常见问题的列举和分析,从不同角度提出作者的观点,对具体问题的解决思路提出立法建议,旨在为解决实际问题提供有效的方案,对公司法律制度的完善有所帮助。 相似文献
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Dynamic characteristics analysis of deployable space structures considering joint clearance 总被引:1,自引:0,他引:1
The clearance in joints influences the dynamic stability and the performance of deployable space structures (DSS). A virtual experimental modal analysis (VEMA) method is proposed to deal with the effects of joint clearance and link flexibility on the dynamic characteristics of the DSS in this paper. The focus is on the finite element modeling of the clearance joint, VEMA and the modal parameters identification of the DSS. The finite element models (FEM) of the clearance joint and the deployable structure are established in ANSYS. The transient dynamic analysis is conducted to provide the time history data of excitation and response for the VEMA. The fast Fourier transform (FFT) technique is used to transform the data from time domain to frequency domain. The frequency response function is calculated to identify the modal parameters of the deployable structure. Experimental verification is provided to indicate the VEMA method is both a cost and time efficient approach to obtain the dynamic characteristics of the DSS. Finally, we analyze the effects of clearance size and gravity on the dynamic characteristics of the DSS. The analysis results indicate that the joint clearance and gravity strongly influence the dynamic characteristics of the DSS. 相似文献
125.
薄壁内、外半管冲压成形工艺参数模拟优化设计 总被引:2,自引:0,他引:2
针对内、外半管的结构特点,分析计算冲压成形主要工艺参数及毛坯尺寸,运用有限元分析软件ANSYS/LS-DYNA,对内、外半管的成形过程进行了模拟。研究了不同压边力及不同冲压速度对零件拉深成形的影响,分析了零件的成形工艺及其起皱缺陷,优化了毛坯形状,避免了成形过程中的缺陷,获得了理想的毛坯形状和工艺参数。 相似文献
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A formal approach using SysML for capturing functional requirements in avionics domain 总被引:1,自引:0,他引:1
In this work, a Model-Based Systems Engineering approach based on SysML is proposed. This approach is used for the capture and the definition of functional requirements in avionics domain. The motivation of this work is triple: guide the capture of functional requirements, validate these functional requirements through functional simulation, and verify efficiently the consistency of these functional requirements. The proposed approach is decomposed into several steps that are detailed to go from conceptual model of avionics domain to a formal functional model that can be simulated in its operating context. To achieve this work, a subset of SysML has been used as an intermediate modelling language to ensure progressive transformation that can be understood and agreed by system stakeholders. Formal concepts are introduced to ensure theoretical consistency of the approach. In addition, transformation rules are defined and the mappings between concepts of ARP4754A civil aircraft guidelines and SysML are formalized through meta-model. The resulting formalization enables engineers to perform functional simulation of the top-level functional architecture extracted from operational scenarios. Finally, the approach has been tested on an industrial avionics system called the Onboard Maintenance System. 相似文献
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贴装优化问题直接关系到表面贴装工艺的效率。本文以JUKI.2010/2020贴片机为试验平台,根据该机型结构及贴装过程,把贴装优化问题的描述为最小权重匹配问题(MWMP)以及非对称旅行商(TSP)问题,构建了一种新的优化模型:把时间优化转化为距离优化,并应用启发式算法进行软件编程。通过生产企业的6块PCB板的对比实验,证明了该数学模型和算法是合理的。 相似文献