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911.
In this paper,a Doppler scaling fast Fourier transform (Doppler-FFT) algorithm for filter bank multi-carrier (FBMC) is proposed,which can efficiently eliminate the impact of the Doppler scaling in satellite communications.By introducing a Doppler scaling factor into the butterfly structure of the fast Fourier transform (FFT) algorithm,the proposed algorithm eliminates the differences between the Doppler shifts of the received subcarriers,and maintains the same order of computational complexity compared to that of the traditional FFT.In the process of using the new method,the Doppler scaling should be estimated by calculating the orbital data in advance.Thus,the inter-symbol interference (ISI) and the inter-carrier interference (ICI) can be completely eliminated,and the signal to interference and noise ratio (SINR) will not be affected.Simulation results also show that the proposed algorithm can achieve a 0.4 dB performance gain compared to the frequency domain equalization (FDE) algorithm in satellite communications. 相似文献
912.
高校思政课教学最突出的特点是其理论性很强,这也正是学生觉得枯燥无味的地方,而这一年龄段的学生,其思维的独立性、全面性、深刻性与批判性有了很大发展,喜欢探究事情背后的原因。因此,要增强高校思政课教学实效,关键还在于思政课教师在教学活动中能否"以理服人",而要做到"以理服人",就要求教师要加强科研,以科研促教学;要创新教学方法和艺术,培养学生理论联系实际的能力;在教学过程中处理好政治性与学术性的关系。 相似文献
913.
The milling stability of thin-walled components is an important issue in the aviation manufacturing industry,which greatly limits the removal rate of a workpiece.However,for a thin-walled workpiece,the dynamic characteristics vary at different positions.In addition,the removed part also has influence on determining the modal parameters of the workpiece.Thus,the milling stability is also time-variant.In this work,in order to investigate the time variation of a workpiece's dynamic characteristics,a new computational model is firstly derived by dividing the workpiece into a removed part and a remaining part with the Ritz method.Then,an updated frequency response function is obtained by Lagrange's equation and the corresponding modal parameters are extracted.Finally,multi-mode stability lobes are plotted by the different quadrature method and its accuracy is verified by experiments.The proposed method improves the computational efficiency to predict the time-varying characteristics of a thin-walled workpiece. 相似文献
914.
Zhongchao Liang Haibo Gao Liang DingZongquan Deng Jianjun Qu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
To investigate and improve the mobility of the Lunar Roving Vehicle (LRV), it is necessary to consider the mechanical properties of the interaction between the wheels and the ground. In this paper, a new solution method, the forced-slip solution method, which uses a semi-empirical approach, was presented. That is, given the wheel’s vertical load and drawbar pull or driving torque as known input values, the unknown slip ratio can be resolved. The alternative method involves predicting the mechanics for a given slip ratio. The proposed method correlates better with actual wheel movements, and by studying a single wheel, this solution method can also be used to resolve the mechanical properties of the front and rear wheels in a four-wheel-drive (4WD) LRV configuration. It can also be used to consider the multi-pass effect of the rear wheels on lunar soil. The calculation results show that the 4WD LRV driving efficiency varies with the position of the center of mass. Thus, the LRV driving efficiency can be optimized by adjusting the position of its center of mass. 相似文献
915.
吴玥 《西安航空技术高等专科学校学报》2011,29(4):95-96
司马相如是汉赋的奠基者,在总结自己创作心得时提出"赋心"、"赋迹"两个文学理论问题,对其他汉赋作家有重要影响。从盛世文人心态、汉人普遍的社会理想方面分析司马相如赋作的传播效应以及审美期待。 相似文献
916.
赵楠 《西安航空技术高等专科学校学报》2014,(6):60-64
有效的课堂教学策略对提高大学教学质量、促进学生有效学习具有十分重要的意义。因此,在教学中,教师应当深入研究大学课堂教学策略,从而提升教学效果。以"西安导游必备"课程为例,根据策略设计的分类、原则和步骤,就有效课堂教学进行设计,以期日后在更多课堂中应用推广。 相似文献
917.
918.
Combined and interactive effects of interference fit and preloads on composite joints 总被引:3,自引:3,他引:0
The combined and interactive effects of the bolt-hole fit conditions and the preloads of the fasteners on the load carrying capacity of single-lap composite-to-titanium bolted joints have been investigated both experimentally and numerically. Quasi-static tests of the hybrid joints with different fit conditions are implemented, and a three dimensional finite element progressive failure analysis model is proposed to predict the influences of the bolt-hole fit conditions and fastener's pre- loads on the mechanical behaviors of the joints. Based on the experimental validated simulation method, a multi-factor, mixed levels orthogonal design table and the analysis of variance method are used to arrange the simulation conditions and to further study the interactive effects of preloads and fit conditions. Through the analysis of the results, for the researched double bolt, single-lap composite-titanium joints, it is found that: the effects of both the interference fit and the preloads change from positive into negative mode with the increase of the interference fit values or preload values; appropriate bolt-hole fit conditions and preloads can improve the bolt-hole contact conditions of the loaded joints, and then retard the fiber failures around the fastener holes, and increase the load carrying capacity of the joints eventually; the interactive effect of the bolt-hole interference fit conditions and preloads cannot be ignored and the parameters need to be considered together and synthetically as the joints are being optimized. 相似文献
919.
920.
CCD光斑质心算法的误差分析 总被引:1,自引:0,他引:1
文章建立了CCD噪声和像元尺寸对质心算法影响的误差模型.模型表明,当CCD上光斑的束腰ω<0.1个像元时,质心算法的误差大于0.28个像元;当束腰ω>0.5个像元时,像元尺寸对灰度质心算法的影响可忽略不计,影响质心算法的主要因素是CCD随机噪声误差.在ω>0.5个像元的前提下,光斑尺寸越小,质心算法的精度越高.实验与理... 相似文献