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排序方式: 共有304条查询结果,搜索用时 921 毫秒
71.
乔女 《航空精密制造技术》2017,53(2)
通过编写APDL命令流,结合ANSYS系统中的"单元生死"技术,动态模拟并仿真了ABS材料在打印过程中温度场的分布,经分析后可以明显看出在不同时刻整体温度场的分布情况,确定温度变化波动范围,温差较大的位置,并结合温度场的云图分析结果确定应力分布不平稳位置,明确Z向不能作为精基准平面。 相似文献
72.
High volume fraction SiCp/Al aluminum matrix composite possesses a variety of outstanding properties,such as high thermal conductivity and low coefficient of thermal expansion.It is widely applied in many fields,especially in automotive and aerospace.An orthogonal experiment is conducted to study the effects of relevant parameters on the mechanical properties by CO2 laser.Then the micro-hardness in different regions is measured.The effects of such parameters as laser power,middle layer thickness and welding speed on the tensile strength of the welded joints are discussed.The experimental results indicate that the maximum of the tensile strength of the welded joints is attained at the laser power of 1 200 W,the welding speed of 1.5 m/min and the middle layer thickness of 0.3 mm.In addition,the mechanism of the improvement of micro-hardness on the weld bead is also analyzed. 相似文献
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通过定性和定量相结合的方法对飞行学员的英语自主学习情况进行了试验性研究。结果表明,飞行学员具有很强的自主学习意识,对英语学习态度积极,但学员自我管理能力较差,在学习中不善于制定计划,对学习环境和教师有很大的依赖,他们重视语言学习的过程而对语言学习的结果表示无所谓。此次调查为英语教师开展教学活动提供了建设性建议,教师应该督促学生制定计划,为学生创造英语学习环境,同时加大课堂语言输入量及输入的质量,对学生学习实施阶段性评价和终结性评价体系。 相似文献
76.
Mingkun Su Yanxi Yang Lei Qiao Xuyang Teng Huina Song 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(2):868-882
This study proposes an enhanced multipath mitigation method based on multi-resolution carrier-to-noise-ratio (CNR) model and adaptive statistical test strategy for real-time kinematic precise point positioning (PPP) applications. The multi-resolution CNR model is established with GPS observation data collected from DOY 152 to 181 of 2019 by 230 globally distributed IGS stations, which used to analyze the relevant factors affecting CNR. Statistical results indicate that the CNR is not only related to the satellite elevation, but also closely related to the receiver types and specific satellite. The maximum difference between different receivers can reach 20 dB for the same satellite at the same elevation. In addition, the performance of the CNR is also obviously different between each satellite, and the maximum difference between different satellites is about 10 dB for the same receiver at the same elevation. Hence, in terms of the method which is based on CNR information for multipath detection and mitigation, the independence of receiver types, satellite and frequency must be considered. With the above analysis, this study developed a multi-resolution CNR model based on different receiver types, different satellites and different elevation firstly. Then, combined with the adaptive statistical test strategy which is based on the difference of CNR between inter-frequency and the difference of CNR between adjacent epochs, the multipath can be detected effectively. For the epoch which affected by multipath, the down-weighted strategy based on CNR is adopted to mitigate the influence of multipath on positioning. Real-time kinematic PPP data are collected to assess the proposed method, and the results demonstrate that the proposed method can detect the multipath effectively, and the detection rate can reach 90.28%. Moreover, after adopting the mitigation strategy, the RMS bias of the east, north and up components are improved about 19.95%, 17.89% and 23.07% compared to the original results, respectively. It is worth noting that this proposed method is also suitable for other GNSS, such as GLONASS and BDS, but the corresponding CNR model must be established simultaneously. 相似文献
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欧拉方程多段翼型绕流计算的嵌套网格方法 总被引:1,自引:0,他引:1
本文采用嵌合体埋入技术,将主段翼型和襟翼分成两子域,对多段翼型的复杂构型进行了分区迭代求解,在有限体体积离散的基础上,求解欧拉方程计算各子域流场的解,通过各流场的耦合迭代到多段翼型绕流的解,典型的带30%襟翼GA(W)-1翼型算例表明,该计算方法稳定,能较地模拟多段翼型中主段翼型与襟翼交接处的复杂流动现象计算结果与实验值有较好的一致性。 相似文献
80.
飞机座舱风挡层合玻璃弹穿有限元分析 总被引:5,自引:0,他引:5
讨论了飞机风挡层合玻璃的抗弹穿叠层设计方法,建立了风挡层合玻璃三维有限元分析模型。对层合玻璃材料采用具有失效模型的弹塑性本构关系,用非线性Lagrange有限元程序模拟了飞机层合玻璃的子弹穿透动响应过程,给出了层合玻璃弹穿的计算实例,数值分析为防弹层合玻璃的设计提供了理论依据。 相似文献