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991.
992.
对碳纤维-玄武岩纤维混杂增强树脂基复合材料最优混杂比范围进行研究。以碳纤维与玄武岩纤维平纹织物为增强体,制备9种具有不同混杂比的混杂纤维复合材料(Hybrid Fiber Reinforced Polymer,HFRP)试样,并进行拉伸实验。依据平纹织物结构特点,计算得出平纹织物单胞性能参数,在ANSYS中,以SHELL181壳单元体建立HFRP有限元模型。该模型对试样刚度的模拟值与实验值近似。分析模型受力时的应力云图发现,存在将HFRP破坏形式分为一次破坏与二次破坏的临界混杂比。有限元模拟研究树脂含量为45%时,不同混杂比的HFRP刚度、强度和拉伸极限应变。当混杂比为60%时,可保证HFRP强度无折减的情况下,较玄武岩复合材料(Basalt Fiber Reinforced Polymer,BFRP)刚度提高93.4%,较碳纤维复合材料(Carbon Fiber Reinforced Polymer,CFRP)拉伸极限应变提高11.3%。 相似文献
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994.
Shih-Chun Pang Ta-Kang Yeh Jing-Shan Hong Chieh-Hung Chen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(8):2333-2346
Because of global warming, global sea levels have risen, the frequency of drought in Taiwan is much more frequent in winter and spring, and rainfall tends to concentrate in summer. The probability of disaster-type weather has also increased significantly. Estimating precipitable water vapor (PWV) through GPS signals, related studies and analyses of weather conditions, and the effective use of meteorological forecasts have been valued by many meteorological research organizations and officials. In this study, PWV data from 2006 to 2017 and rainfall data were used for long-term harmonic analysis. PWV data calculated by ECMWF (ECMWF-PWV) and PWV data calculated by GPS (GPS-PWV) were subjected to regression analysis to verify the reliability of the GPS-PWV data. The research results show that GPS-PWV and ECMWF-PWV have extremely high correlations; however, the climatic characteristics of some regions and the high spatial resolution of GPS-PWV are able to accurately calculate the high topographic relief of small areas. It is judged that the GPS-PWV is more accurate than the ECMWF-PWV. It is worth noting that the PWV trend of the regions during the 6-year-before period has not changed very much, but the rainfall trend has changed obviously. Except for the eastern region, most of the regions show a decreasing trend year by year. More long-term observations are still needed to prove whether this phenomenon relates to global warming. Long-term rainfall analysis showed that the topography blocked water vapor to the western, southern, and mountainous regions, making them distinctly wet or dry. The harmonic curve showed great consistency with the peaks of PWV and rainfall. However, in the northern and eastern parts of the windward side, the time when maximum rainfall occurred each year may be one month later than the time when the maximum PWV value occurred each year. The reason for this difference is likely to be a decrease in the number of autumn typhoons, resulting in a nearly one-month difference in PWV peaks and rainfall peaks. Finally, we analyzed the linear trend of GPS-PWV and temperature for all regions in Taiwan, and found that annual increasing rate of GPS-PWV and temperature of all regions are within 0.4–0.5 mm/year and 0.04–0.11 C°/year, respectively. 相似文献
995.
A flight dynamics model based on elastic blades for helicopters is developed. Modal shape analysis is used to describe the rotating elastic blades for the purpose of reducing the elastic degrees of freedom for blades. The analytical result is employed to predict the rotor forces and moments. The equilibrium equation of the flight dynamics model is then constructed for the elastic motion for blades and the rigid motion for other parts. The nonlinear equation is further simplified, and the gradient descent algorithm is adopted to implement the trim simulation. The trim analysis shows that the effect of blade elasticity on the accuracy of rotor forces and moments is apparent at high speed, and the proposed method presents good accuracy for trim performance. The time-domain response is realized by a combination of the Newmark method and the adaptive Runge-Kutta method. The helicopter control responses of collective pitch show that the response accuracy of the model at a yaw-and-pitch attitude is improved. Finally, the influence of blade elasticity on the helicopter dynamic response in low-altitude wind shear is investigated. An increase in blade elastic-ity reduces the oscillation amplitude of the yaw angle and the vertical speed by more than 70%. Compared with a rigid blade, an elastic blade reduces the vibration frequency of the angular veloc-ity and results in a fast return of the helicopter to its stable flight. 相似文献
996.
王虹 《北华航天工业学院学报》2010,20(2)
本文通过对以英语为口译的原、译语录音资料的分析,从意义储存方式、译语的搜觅等方面发现两种译员的相同和不同之处,对于以英语为官方语的译员和以英语为外语的译员的区别,提出了新的观点。同时,借鉴个案研究的结果,将其运用于口译教学中,以提高口译教学的效果。 相似文献
997.
998.
对于飞机性能设计来讲,Altair公司的Hyper-Works是一种高效、优化、创新的技术,应对了新一代飞机设计对CAE技术提出的挑战,在A380、A350、A30X、波音787、F35等机型的设计中得到大量应用,解决了大量实际设计问题,是现代飞机性能设计的新一代平台. 相似文献
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1000.