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921.
为解决航空发动机机载健康管理系统正向设计流程不清晰、设计需求不明确、需求设计对应及追溯不规范的问题,在对
比国内外现有健康管理功能架构体系的基础上,结合正向设计中需求捕获、需求分析和功能分配,研究了由上到下的航空发动机
健康管理系统正向设计基本流程,开发了航空发动机健康管理正向设计流程平台,实现了机载功能架构的设计。引入基于模型的
系统工程思想,采用面向对象的工程设计思路,建立功能目标量化、功能描述、模块定义等图形化设计方法,验证了该设计方法在
硬件设计中的可用性。通过研究航空发动机机载健康管理系统设计方法并分析机载功能组成,建立了可扩展的流程平台,基于模
型设计方法建立了可用的硬件设计模型,可为航空发动机机载健康管理系统设计提供参考。 相似文献
922.
Wei Wang Bin Zhao Qi Wang Shaomin Yang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The Crustal Movement Observation Network of China (CMONOC) is one of the major scientific infrastructures, mainly using Global Positioning System (GPS) measurements, to monitor crustal deformation in the Chinese mainland. In this paper, decade-long coordinate time series of 26 continuous GPS sites of CMONOC are analyzed for their noise content using maximum likelihood estimation (MLE). We study the noise properties of continuous GPS time series of CMONOC for the unfiltered, filtered solutions and also the common mode signals in terms of power law plus white noise model. In the spatial filtering, we remove for every time series a common mode error that was estimated from a modified stacking of position residuals from other sites within ∼1000 km of the selected site. We find that the common mode signal in our network has a combination of spatially correlated flicker noise and a common white noise with large spatial extent. We demonstrate that for the unfiltered solutions of CMONOC continuous GPS sites the main colored noise is a flicker process, with a mean spectral index of ∼1. For the filtered solutions, the main colored noise is a general power law process, indicating that a major number of the filtered regional solutions have a combination of noise sources or local effects. The velocity uncertainties from CMONOC continuous GPS coordinate time series may be underestimated by factors of 8–16 if a pure white noise model is assumed. In addition, using a white plus flicker noise model, the median values of velocity errors for the unfiltered solutions are 0.16 (north), 0.17 (east) and 0.58 (vertical) mm/yr, and the median values for the filtered solutions are 0.09 (north), 0.10 (east) and 0.40 (vertical) mm/yr. 相似文献
923.
谭晓阳 《沈阳航空工业学院学报》2011,28(1):39-45
正确理解和跟踪人脸是构建能够在复杂人类环境中自主工作的智能机器系统的首要和关键步骤,可形变模型通过统计学习方法给出对象形状的紧凑数学表示,是达成这一目标的重要手段。从机器学习和计算机视觉领域角度,对人脸图像的可形变模型构建这一研究课题的最新研究进展进行了综述。特别地,对其中涉及的关键问题进行了归纳,并建立了一个抽象的统一贝叶斯可形变模型;在此框架下,对标准的点分布模型PDM模型及其最新研究进展进行了回顾、对一些主要的方法进行了介绍、对这些方法优缺点进行了对比分析。 相似文献
924.
925.
Parametric analyses for synthetic jet control on separation and stall over rotor airfoil 总被引:1,自引:1,他引:1
Numerical simulations are performed to investigate the effects of synthetic jet control on separation and stall over rotor airfoils. The preconditioned and unsteady Reynolds-averaged Navier–Stokes equations coupled with a k x shear stream transport turbulence model are employed to accomplish the flowfield simulation of rotor airfoils under jet control. Additionally,a velocity boundary condition modeled by a sinusoidal function is developed to fulfill the perturbation effect of periodic jets. The validity of the present CFD procedure is evaluated by the simulated results of an isolated synthetic jet and the jet control case for airfoil NACA0015. Then, parametric analyses are conducted specifically for an OA213 rotor airfoil to investigate the effects of jet parameters(forcing frequency, jet location and momentum coefficient, jet direction, and distribution of jet arrays) on the control effect of the aerodynamic characteristics of a rotor airfoil. Preliminary results indicate that the efficiency of jet control can be improved with specific frequencies(the best lift-drag ratio at F+= 2.0) and jet angles(40 or 75) when the jets are located near the separation point of the rotor airfoil. Furthermore, as a result of a suitable combination of jet arrays, the lift coefficient of the airfoil can be improved by nearly 100%, and the corresponding drag coefficient decreased by26.5% in comparison with the single point control case. 相似文献
926.
927.
Yueyuan Hu Patrick Lau Christa Baumstark-Khan Christine E. Hellweg Günther Reitz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
To evaluate the effects of ionizing radiation (IR) on murine preosteoblastic cell differentiation, we directed OCT-1 cells to the osteoblastic lineage by treatment with a combination of β-glycerophosphate (β-GP), ascorbic acid (AA), and dexamethasone (Dex). In vitro mineralization was evaluated based on histochemical staining and quantification of the hydroxyapatite content of the extracellular bone matrix. Expression of mRNA encoding Runx2, transforming growth factor β1 (TGF-β1), osteocalcin (OCN), and p21CDKN1A was analyzed. Exposure to IR reduced the growth rate and diminished cell survival of OCT-1 cells under standard conditions. Notably, calcium content analysis revealed that deposition of mineralized matrix increased significantly under osteogenic conditions after X-ray exposure in a time-dependent manner. In this study, higher radiation doses exert significant overall effects on TGF-β1, OCN, and p21CDKN1A gene expression, suggesting that gene expression following X-ray treatment is affected in a dose-dependent manner. Additionally, we verified that Runx2 was suppressed within 24 h after irradiation at 2 and 4 Gy. Although further studies are required to verify the molecular mechanism, our observations strongly suggest that treatment with IR markedly alters the differentiation and mineralization process of preosteoblastic cells. 相似文献
928.
针对某型飞机进行二元推力矢量改装时对发动机出口的气流进行过渡转换的问题,设计了喷管导流管,将导流管气流截面由圆形过渡到长方形。本文利用有限元软件PATRAN对导流管进行了应力强度分析和变形分析,得出导流管的应力分布场和变形位移场,通过对不同厚度的导流管的分析计算得出导流管最大应力和最大位移随管壁厚度变化曲线,从而确定最佳的管壁厚度。研究了导流管最大应力和最大位移沿轴向的变化曲线,并对导流管的结构进行了优化设计,给出两种优化设计方案,得到较为理想的结构。 相似文献
929.
本文介绍了在某球墨铸铁曲轴生产厂,采用磁粉和超声波无损检测方法对曲轴进行探伤,并对探伤中发现缺陷进行了统计分析,找出了缺陷多发部位,并就产生缺陷的原理及形成机理进行了分析,提出了相应的预防措施,以期对球墨铸铁曲轴生产者有所帮助。 相似文献
930.
本文根据人体的热调节机制建立了二维人体热调节的有限元模型,并设计了相应的实验对该模型进行了验证,实验结果与计算结果吻合较好,本模型对于以人体-环境热交换为内容的工程实践和理论研究有较高的应用价值。 相似文献