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81.
Stationary flow fields prediction of variable physical domain based on proper orthogonal decomposition and kriging surrogate model 总被引:2,自引:2,他引:0
In this paper a new flow field prediction method which is independent of the governing equations, is developed to predict stationary flow fields of variable physical domain. Predicted flow fields come from linear superposition of selected basis modes generated by proper orthogonal decomposition(POD). Instead of traditional projection methods, kriging surrogate model is used to calculate the superposition coefficients through building approximate function relationships between profile geometry parameters of physical domain and these coefficients. In this context,the problem which troubles the traditional POD-projection method due to viscosity and compressibility has been avoided in the whole process. Moreover, there are no constraints for the inner product form, so two forms of simple ones are applied to improving computational efficiency and cope with variable physical domain problem. An iterative algorithm is developed to determine how many basis modes ranking front should be used in the prediction. Testing results prove the feasibility of this new method for subsonic flow field, but also prove that it is not proper for transonic flow field because of the poor predicted shock waves. 相似文献
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Almost all work on model-based diagnosis (MBD) potentially presumes faults are per- sistent and does not take intermittent faults (IFs) into account. Therefore, it is common for diag- nosis systems to misjudge IFs as permanent faults (PFs), which are the major cause of the problems of false alarms, cannot duplication and no fault found in aircraft avionics. To address this problem, a new fault model which includes PFs and IFs is presented based on discrete event systems (DESs). Thereafter, an approach is given to discriminate between PFs and IFs by diagnosing the current fault. In this paper, the regulations of (PFs and IFs) fault evolution through fault and reset events along the traces of system are studied, and then label propagation function is modified to account for PFs and the dynamic behavior of IFs and diagnosability of PFs and IFs are defined. Finally, illustrative examples are presented to demonstrate the proposed approach, and the analysis results show the fault types can be discriminated within bounded delay if the system is diagnosable. 相似文献
83.
Moschopoulos G. Mei Qiu Pinheiro H. Jain P. 《IEEE transactions on aerospace and electronic systems》2003,39(2):660-674
A pulsewidth modulated (PWM) full-bridge converter that simultaneously performs input power factor correction (PFC) and DC-DC conversion is proposed. The converter is the same as the standard voltage-fed PWM full-bridge converter with a diode-bridge low-pass filter front end, but with a slight modification that results in an improvement in power factor that is sufficient to satisfy the EN61000-3-2 requirements for electrical equipment. The operation of the converter is explained and analyzed, and the results of the analysis are used to determine the converter's steady-state characteristics, which are discussed in detail. A design procedure for the selection of components is then derived and demonstrated with an example. The feasibility of the converter and its ability to satisfy EN61000-3-2 requirements on electrical equipment is shown with results obtained from an experimental prototype. 相似文献
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大型星载可展开天线的展开动力学问题 总被引:4,自引:0,他引:4
针对大型星载可展开天线所具有的尺寸大、刚性小、展开机构复杂,所处环境恶劣等特点,结合天线的构形特征,着重从可展开天线展开动力学的建模角度,综述了可展开天线的展开动力学问题。对解决途径及办法提出了一些看法。 相似文献
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在结构疲劳寿命服从双参数Weibul分布假设的基础上,通过结构细节疲劳额定值的概念给出了结构破坏危险率与使用寿命的关系式,并通过实例计算得出了破坏危险率-寿命曲线。 相似文献