铝合金搅拌摩擦焊表面冷喷涂层的结构与耐蚀性

采用冷喷涂技术在2219铝合金搅拌摩擦焊接头上制备Al涂层,以提高搅拌摩擦焊接头耐蚀性。通过数字显微镜、扫描电镜、电化学工作站对Al涂层的结构及耐蚀性进行表征。结果表明:冷喷Al涂层质量良好,孔隙率仅为0.77%,涂层内部存在等轴晶、细化晶粒以及拉长晶粒,涂层界面以机械咬合为主,涂层/接头区界面质量明显优于涂层/母材区界面;电化学数据显示,涂层腐蚀敏感性较低,自腐蚀电位和腐蚀电流密度均低于热影响区,冷喷涂层降低了搅拌摩擦焊接头的腐蚀敏感性;晶间腐蚀实验表明,腐蚀6 h后,涂层最大腐蚀深度仅为热影响区最大腐蚀深度的50%,证明冷喷涂技术显著改善了搅拌摩擦焊接头的耐腐蚀性。     

强化词块训练 提高英语听说能力

以词块教学理论为依据,分析在听说教学中进行词块训练的可行性。研究词块训练在听说课堂中的具体实施过程,并通过问卷调查和访谈结果,论证了听说课上引入词块理念能提高英语学习者听说能力从而提出词块学习对语言习得的有效性。     

一种推广的靶效应模型及其对剂量-存活率的拟合探讨

辐射生物物理模型对于准确、有效地评估空间辐射引起的生物损伤及风险具有重要意义。目前较为流行的基于地基模拟的“靶效应模型”和“非靶效应模型”，是进一步探索空间辐射生物物理模型的基础。在考虑了辐射的非靶效应和机体复杂的修复过程的基础上，将传统理论中“击中”即“失活”的线性关系进行了推广，提出了基于否定算子的靶效应模型。通过对辐射钝感和敏感的两类细胞辐射实验中剂量与细胞存活率数据进行拟合发现，对于正常皮肤成纤维细胞的存活率数据，经典的靶学说与基于否定算子的改进靶效应模型都有较好的拟合效果；而对于人类胚胎肝细胞的存活率数据，基于否定算子的改进靶效应模型的拟合结果明显优于传统的靶学说模型。拟合结果中的模型参数值在人成纤维细胞和胚胎肝细胞中明显不同，说明了本模型的参数与传能线密度，细胞的种类、以及修复能力等物理和生物因素有关。     

Modified fast Fourier transform in FBMC for satellite communications

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.     

高校思政课教学中“以理服人”的路径探析

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。     

A novel stability prediction approach for thin-walled component milling considering material removing process

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.     

Analysis of driving efficiency for LRV wheels using forced-slip method

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.     

司马相如“赋心”“赋迹”说的传播效应和审美期待

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。     

有效课堂教学策略的设计——以“西安导游必备”课程为例

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。     

原始疲劳质量评定和裂纹扩展方法研究

在对带有一个铆接孔的试件进行试验研究的基础上,利用性能退化失效曲线,提出了一种新的初始疲劳质量和裂纹扩展速率的确定方法。根据试验结果和理论推导,建立了裂纹扩展长度与加载循环次数的函数关系。在此基础上,估算了EIFS值,并用指数函数拟合方法估计了疲劳裂纹扩展速率。最后通过对临界裂纹尺寸的理论计算验证了新方法的可行性和有效性。