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221.
任丽 《长沙航空职业技术学院学报》2014,14(4):23-26
从生态学视角出发,分析了大学英语教学的生态系统;探讨了实现生态化大学英语教学应该遵循的原则,即可持续发展原则以及生态系统的整体性、开放性和动态平衡的原则;在这些原则的指导下,本文借鉴生态学的相关理论和观点探索了优化大学英语教学的途径和模式,以期通过跨学科的角度探索和推动大学英语教学的发展。 相似文献
222.
曹琳华 《中国民航飞行学院学报》2014,(4):58-61
本文收集了形成性评估在高职英语教学中应用研究的文献,进行了分析,总结了前期研究的局限,并对后期研究提出了一些建议。 相似文献
223.
Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and flexibility.The surface machining consistency, however,is difficult to be guaranteed in such a process.To overcome this problem, a method of hybrid force-position control combined with PI/PD control is proposed to be applied in robotic abrasive belt grinding of complex geometries.Voltage signals are firstly obtained and transformed to force information with signal conditioning methods.Secondly, zero drift and gravity compensation algorithms are presented to calibrate the F/T transducer which is installed on the robot end-effector.Next, a force control strategy combining hybrid force-position control with PI/PD control is introduced to be employed in robotic abrasive belt grinding operations where the force control law is applied to the Z direction of the tool frame and the positon control law is used in the X direction of the tool frame.Then, the accuracy of the F/T transducer and the robotic force control system is analyzed to ensure the stability and reliability of force control in the robotic grinding process.Finally, two typical cases on robotic belt grinding of a test workpiece and an aero-engine blade are conducted to validate the practicality and effectiveness of the force control technology proposed. 相似文献
224.
Willy Benz 《Space Science Reviews》2000,92(1-2):279-294
The physics of low velocity collisions (5 m/s to 40 m/s) between basalt bodies ranging in size from 1 m to 10 km is studied
in an effort to investigate the early phases of planetesimal accretions. To assess the importance of the internal structure
of planetesimals on the outcome of the collisions, we model them either as solid spheres or as rubble piles with a filling
factor of 0.5.
The collisions are simulated using a three dimensional Smooth Particle Hydrodynamics (SPH) code that incorporates the combined
effects of material strength and a brittle fragmentation model. This approach allows the determination not only of the mass
of the largest fragments surviving the collisions but also their dynamical characteristics.
We find that low velocity collisions are for equal incoming kinetic energy per gram of target material considerably more efficient
in destroying and dispersing bodies than their high velocity counterparts. Furthermore, planetesimals modeled as rubble piles
are found to be characterized by a disruption threshold about 5 times smaller than solid bodies. Both results are a consequence
of a more efficient momentum transfer between projectile and fragments in collisions involving bodies of comparable sizes.
Size and shape dependent gas drag is shown to provide relative collision velocities between similar meter-sized objects well
in excess of the critical disruption threshold of either rubble piles or solid bodies. Unless accretion can proceed avoiding
collisions between bodies of similar masses, the relative weakness of bodies in this size range creates a serious bottleneck
for planetesimal growth.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
225.
张换成 《中国民航飞行学院学报》2012,(6):72-75
分析了网络化语境中英汉交际语言的产生与形式,指出了影响其发展的主要因素。同时就网络化语境中英汉交际语言的规范化问题及其发展前景进行了探讨。 相似文献
226.
李俊波 《华北航天工业学院学报》2012,(1):35-37
本文从社会需要出发分析了专业人才的英语素质和大学英语综合应用能力培养过程中的问题,提出了搞好大学英语自身特色建设的建议,倡导基于专业人才培养定位的大学英语综合应用能力培养。 相似文献
227.
Sylvain Chaty 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
In this review I first describe the nature of the three kinds of High-Mass X-ray Binaries (HMXBs), accreting through: (i) Be circumstellar disc, (ii) supergiant stellar wind, and (iii) Roche lobe filling supergiants. 相似文献
228.
L. S. Anderson-Huang 《Space Science Reviews》1998,85(1-2):203-213
The chromosphere-corona transition region of the Sun enjoys both simplicities of character and complexities of character which
result from its very thin geometrical extent. The simplicities derive from the reasonably clear view of the energy balance
(both observationally and theoretically), while the complexities derive from both the proximity of the not-so-clearly viewed
regions below and above, and the almost certain convolutions and perhaps discontinuities in the three dimensional geometry
of the transition sheet. While observational resolution and spectral information has improved greatly in recent years, the
problems associated with a single vantage point, the Earth and its environs, have not gone away. To understand the transition
region we must resolve structures radially and temporally as well as in the plane of the sky.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
229.
孙定浩 《空间控制技术与应用》2011,37(5):26-30
用分析法全面讨论脉宽调制器(IC:1842/3/4/5,1842A/3A/4A/5A)中振荡器的振荡特征参数(占空比D和频率f)与外接电阻R和电容C的关系.我们得到以R、C为自变量表达D和f的函数,以D、f为自变量求R、C的函数.并根据这些函数的计算结果绘制描述D、f、R、C(1F)4个参数之间的关系曲线.这些结果,不仅提升了对这类振荡器的认知,而且可供设计时直接引用和参考. 相似文献
230.
都建秀 《西安航空技术高等专科学校学报》2011,29(4):53-56
以系统功能语法理论的主位推进模式为基本框架,以英文摘要为研究对象,探讨主位推进模式在这一语篇体裁中的应用,并统计分析英文摘要中基本的主位推进模式选择取向。 相似文献