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901.
《中国航空学报》2016,(2):520-533
Damping improvement in composite structures via introducing nanofillers generally has remarkable negative effects on the other mechanical properties. Therefore, in the present work, Si C and Al_2O_3 nanoparticles' infusion effects on the flexural, interfacial and vibration properties of epoxy matrix and glass fiber reinforced epoxy(GFR/E) laminates were investigated. Unidirectional(UD-GFR/E) and quasi-isotropic(QI-GFR/E) laminates with [0/±45/90]sand [90/±45/0]sstacking sequences were hybridized by the optimum nanoparticles percentages. Results from off-axis flexural strengths of UD-GFR/E demonstrate good fiber/nanophased-matrix interfacial bonding.The interlaminar shear stress between the adjacent layers with different orientations/strains of ductile QI-GFR/Si C/E laminates results in decreasing the flexural strengths respectively by 24.3% and9.1% for [0/±45/90]sand [90/±45/0]sstacking sequences and increasing the dissipated interfacial friction energy and thus the damping by 105.7% and 26.1%. The damping of QI-GFR/E,QI-GFR/Si C/E and QI-GFR/Al_2O_3/E laminates with [90/±45/0]sstacking sequence was increased by 111.4%, 29.7% and 32.9% respectively compared to [0/±45/90]sstacking sequence. 相似文献
902.
903.
904.
Junoh Jung Sang-Young Park Sung-Woo Kim Youngho Eun Young-Keun Chang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
A nonlinear control technique pertaining to attitude synchronization problems is presented for formation flying spacecraft by utilizing the State-Dependent Riccati Equation (SDRE) technique. An attitude controller consisting of relative control and absolute control is designed using a reaction wheel assembly for regulator and tracking problems. To achieve effective relative control, the selective state-dependent connectivity is also adopted. The global asymptotic stability of the controller is confirmed using the Lyapunov theorem and is verified by Monte-Carlo simulations. An air-bearing-based Hardware-In-the-Loop Simulator (HILS) is also developed to validate the proposed control laws in real-time environments. The SDRE controller is discretized for implementation of a real-time processor in the HILS. The pointing errors are about 0.2° in the numerical simulations and about 1° in the HILS simulations, and experimental simulations confirm the effectiveness of the control algorithm for attitude synchronization in a spacecraft formation flying mission. Consequently, experiments using the HILS in a real-time environment can appropriately perform spacecraft attitude synchronization algorithms for formation flying spacecraft. 相似文献
905.
建立翼型气动数据库对翼型的选择和设计具有重要的意义。本文基于一种建立翼型通用气动数据库的思想,介绍该数据库的基本框架和基本功能;该数据库采用一种基于可扩展标记语言的通用数据格式进行存储,包含翼型几何特性数据、不同流动状态下力系数、物面压力分布等各种气动数据,并且还可提供灵活多样的数据处理功能;采用代理模型和变可信度模型技术,实现气动数据快速检索和插值功能。通过DU93-W-210翼型算例初步表明如何实现气动数据生成和快速插值,从而初步展示了所提出翼型气动数据库技术的可行性。 相似文献
906.
To evaluate stress corrosion cracking(SCC) mechanism of low alloy ultra-high strength steel 30CrMnSiNi2 A in environment containing NaCl, SCC behavior of the steel in 3.5wt% NaCl solution is investigated by slow strain rate technique(SSRT) with various strain rates and applied potentials, surface analysis technique, and electrochemical measurements. SCC susceptibility of the steel increases rapidly with strain rate decreasing from 1 · 10 5s 1to 5 · 10 7s 1, and becomes stable when strain rate is lower than 5 · 10 7s 1. SCC propagation of the steel in the solution at open circuit potential(OCP) needs sufficient hydrogen which is supplied at a certain strain rate.Fracture surface at OCP has similar characteristics with that at cathodic polarization 1000 mVSCE, which presents characteristic fractography of hydrogen induced cracking(HIC).All of these indicate that SCC behavior of the steel in the solution at OCP is mainly controlled by HIC rather than anodic dissolution(AD). 相似文献
907.
Roberta Paradiso Roberta Buonomo Mike A. Dixon Giancarlo Barbieri Stefania De Pascale 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Soybean [Glycine max (L.) Merr.] is one of the plant species selected within the European Space Agency (ESA) Micro-Ecological Life Support System Alternative (MELiSSA) project for hydroponic cultivation in Biological Life Support Systems (BLSSs), because of the high nutritional value of seeds. Root symbiosis of soybean with Bradirhizobium japonicum contributes to plant nutrition in soil, providing ammonium through the bacterial fixation of atmospheric nitrogen. The aim of this study was to evaluate the effects of two hydroponic systems, Nutrient Film Technique (NFT) and cultivation on rockwool, and two nitrogen sources in the nutrient solution, nitrate (as Ca(NO3)2 and KNO3) and urea (CO(NH2)2), on root symbiosis, plant growth and seeds production of soybean. Plants of cultivar ‘OT8914’, inoculated with B. japonicum strain BUS-2, were grown in a growth chamber, under controlled environmental conditions. 相似文献
908.
在复杂外形流场模拟的嵌合体技术中引入守恒型MFBI算法,以改进传统嵌合体技术中子域间流场信息传递不守恒的缺陷,在标准遗传算法基础上采用分段进化的方式,同时以大迎角状态下的升力系数作为设计目标,针对基础构型的前后缘缝道参数,进行了遗传优化设计。最终的设计结果表明,相较于初始构型,其最大升力系数有明显的提升,且具有良好的失速特性。同时在增升装置嵌合体流场分析和优化设计表明,所采用的守恒型嵌合体技术,在大迎角流场优化中相较于传统的非守恒格式,具有更好的精度以及收敛特性,优化结果得到了一定的提高。 相似文献
909.
《中国航空学报》2020,33(9):2281-2294
This paper presents an analytical, numerical, and experimental study on atomization characteristics and droplet distribution of a twin-fluid two-phase internal mixing atomizer to develop a Maximum Entropy Method (MEM). A two-phase Eulerian-Lagrangian method is utilized for atomization modeling of the inside and outside atomizer. In order to modify energy and momentum sources in the MEM, parametric studies are performed, and experimental tests are carried out to verify the results by applying the shadowgraph method. An advanced test stand is developed to prepare a wide range of changes in atomization characteristics and mixing ratios. A high degree of consistency is found between numerical results from the developed MEM and experimental tests with different gas-phase pressures and liquid flow rates. The droplet diameter and velocity distribution are reviewed based on various Weber numbers, sources of energy, and momentum. Turbulence modeling assists to estimate the breakup length and time scale precisely in the developed MEM, and distribution ranges with mean values are achieved. With reference to a strong correlation between upstream turbulence flow and the developed MEM verified by experimental tests, an ideal droplet size and velocity distribution prediction is observed. 相似文献
910.
孟志华 《郑州航空工业管理学院学报(管理科学版)》2011,29(1)
当前,环境问题已经逐渐超越国界成为一个全球性的问题,世界各国对于环境相关的财务问题尤其是环境会计和环境审计越来越重视,而环境绩效审计是环境审计的重要方面和发展趋势。为了对环境绩效审计研究的发展轨迹与现状得到一个全面、准确的认识,文章在掌握了国内大量相关资料的基础上,运用规范研究方法,对环境绩效审计研究所涉及的定义、内容和方法进行了简要地总结和评价,并对未来的环境绩效审计研究提出了相应的建议,以期丰富我国的环境绩效审计理论。 相似文献