As a novel type of polynomial chaos expansion (PCE), the data-driven PCE (DD-PCE) approach has been developed to have a wide range of potential applications for uncertainty propagation. While the research on DD-PCE is still ongoing, its merits compared with the existing PCE approaches have yet to be understood and explored, and its limitations also need to be addressed. In this article, the Galerkin projection technique in conjunction with the moment-matching equations is employed in DD-PCE for higher-dimensional uncertainty propagation. The enhanced DD-PCE method is then compared with current PCE methods to fully investigate its relative merits through four numerical examples considering different cases of information for random inputs. It is found that the proposed method could improve the accuracy, or in some cases leads to comparable results, demonstrating its effectiveness and advantages. Its application in dealing with a Mars entry trajectory optimization problem further verifies its effectiveness. 相似文献
In this paper, FeCrNiBSiMox (x = 1.0, 1.5, 2.0, 2.5) stainless steels were successfully prepared using a laser melting deposition technology, with the aim to investigate the effect of Mo content on microstructure and corrosion behaviors. The results showed that the as-deposited specimens were composed mostly of α-Fe and a small amount of (Cr, Mo)7C3, and (Cr, Mo)7C3 existed in the inter-dendritic (ID) region. As the Mo content increased, grain refinement could be clearly observed, and the area of the ID region increased from 27% to 54%. The low-angle boundaries accounted for 60–70% of the grain boundaries of the as-deposited specimens. Increasing the content of Mo improved the microhardness of the as-deposited specimens from 652 HV to 813 HV. The corrosion current density of the as-deposited specimens with the Mo mass fractions of 1.0%, 1.5%, 2.0%, and 2.5% were 1.37 × 10−6, 1.02 × 10−7, 6.19 × 10−7, and 3.06 × 10−7 A/cm2, respectively. The as-deposited specimen with Mo content of 1.5% had lower cumulative erosion loss and erosion loss rate than other as-deposited specimens. The FeCrNiBSiMox (x = 1.5) specimen exhibited excellent resistance to electrochemical corrosion and cavitation erosion. 相似文献
The phase transition process of the MnO2 phase with increases in Co2+ doping can be described by the Ouroboros symbol. The undoped sample is pure δ-MnO2 with nanosheets structures. Then a small amount of Co2+ ions changes the final products and generates α-MnO2 nanofibres in the δ-MnO2 matrix. The products become pure α-MnO2 with an appropriate amount of Co added. However, when the Co amount continues to increase, the amount of α-MnO2 decreases in the products and turns back to form pure δ-MnO2 in the end. Analysing the electromagnetic absorption performance, the relationship between the properties and the proportion of δ-MnO2/α-MnO2 in the powders adjusted by Co2+ doping has been explored, and the composites of δ-/α-MnO2 show better absorption ability than the single-phase samples. As a result, the optimal reflection loss (RL) is −54.8 dB, and the effective absorption bandwidth can cover the Ku band at a thickness of 2.2 mm and the X band at a thickness of 3.1 mm with 50 wt.% filler loading ratios. This research might shed new light on the improvement of novel microwave absorption materials.
A macroscopic numerical method is proposed to study the flow distribution uniformity of a novel porous copper fiber sintered felt (PCFSF), which has gradient porosities and was developed as the methanol steam reforming micro-reactor catalyst support for hydrogen production for fuel cell applications. The macroscopic porous media developed by the ANSYS/FLUENT software is used to represent the PCFSF. Our results indicate that the gradient porosity can reshape the flow distribution of PCFSFs greatly, thus producing significant influence on their performance. It is further revealed that, for a PCFSF with a determined gradient porosity configuration but different reactant feed directions, the velocity uniformity can be used as a quantitative criterion to evaluate the performance of hydrogen production. Furthermore, new gradient PCFSFs are produced according to the flow distribution of original gradient PCFSFs. The preliminary experimental results of the new gradient PCFSFs of 0.8-0.9-0.7 and 0.7-0.9-0.8 exhibit better methanol conversion and H2 flow rate. This indicates that the numerical method can be used for the optimization of PCFSFs' gradient porosity configuration, which consists of the shape and position of the interfaces between different porosity portions, the number of interfaces and the porosity distribution in different portions. 相似文献