共查询到20条相似文献，搜索用时 109 毫秒
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在人们的初始印象中,学习数学主要是训练逻辑思维能力。在以往的教学中,特别强调数学的"三性",即抽象性、严谨性、系统性。这固然是一个重要的方面,但我们也不能忽视生动活泼的形象思维在数学教学中的重要作用。该文分析了这两种思维形式的特点、作用和相互关系,从而对数学的创造性思维有一个更全面的认识。 相似文献
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我国是一个历史悠久的文明古国,中华民族一向重视诚实信用这一伦理标准。诚实信用原则作为社会的道德信条,必然关系着一个时代一个国家,一个法律系统对人性的基本认识和基本态度。诚实信用原则在民法条款中是最重要的条款之一,随着司法制度的改革,诚实信用原则在民事诉讼中显示着不可忽视的作用。本文就我国民事诉讼中诚实信用原则的概念、渊源、作用以及适用的法理依据做了简单的阐述。 相似文献
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我国是一个历史悠久的文明古国,中华民族一向重视诚实信用这一伦理标准。诚实信用原则作为社会的道德信条,必然关系着一个时代一个国家,一个法律系统对人性的基本认识和基本态度。诚实信用原则在民法条款中是最重要的条款之一,随着司法制度的改革,诚实信用原则在民事诉讼中显示着不可忽视的作用。本文就我国民事诉讼中诚实信用原则的概念、渊源、作用以及适用的法理依据做了简单的阐述。 相似文献
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加强财务管理是企业可持续发展的一个关键,成本控制在财务管理中有着十分重要的地位和作用。企业应从成本控制着手把财务管理推向一个新的阶段,这是企业目前财务管理的一项重要内容。 相似文献
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从个人主义的积极作用和消极作用两方面的因素来看,如何扬长避短是一个关键问题,而这也是在美国文化中始终没有妥善处理好的“难结”。而对于美国个人主义今后究竟何去何从,是一个值得期待的谜,一个期待唯有时间才能告诉我们谜底的谜。 相似文献
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从个人主义的积极作用和消极作用两方面的因素来看,如何扬长避短是一个关键问题,而这也是在美国文化中始终没有妥善处理好的"难结".而对于美国个人主义今后究竞何去何从,是一个值得期待的谜,一个期待唯有时间才能告诉我们谜底的谜. 相似文献
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我国是一个历史悠久的文明古国,中华民族一向重视诚实信用这一伦理标准.诚实信用原则作为社会的道德信条,必然关系着一个时代一个国家,一个法律系统对人性的基本认识和基本态度.诚实信用原则在民法条款中是最重要的条款之一,随着司法制度的改革,诚实信用原则在民事诉讼中显示着不可忽视的作用.本文就我国民事诉讼中诚实信用原则的概念、渊源、作用以及适用的法理依据做了简单的阐述. 相似文献
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进入二十一世纪以来,我国的城市化建设规模在不断扩大的过程中,交通事业在这一个过程中得到了极大的提升。对于城市的发展来说,交通系统起到了极其重要的持续引导作用,这也是交通系统自身所必须要拥有的一个基础功能。本篇文章主要针对交通安全设施工程施工过程中的相关要点以及其中所存在的问题进行了全面详细的分析,以期为其他城市的交通系统发展提供参考。 相似文献
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利用低温超高真空扫描隧道显微镜,对吸附于金表面的单个钴酞菁分子进行单分子选键化学"手术",成功"剪裁"了分子外围的氢原子,并使其与金属表面形成稳定的化学键.该成果发表在Science上,审稿人给予高度评价,并邀请美国专家撰写专文介绍和评述该成果. 相似文献
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Chaotic attitude motion of a magnetic rigid spacecraft in a circular orbit near the equatorial plane
This paper deals with chaotic attitude motion of a magnetic rigid spacecraft in a circular orbit near the equatorial plane of the earth. The dynamical model of the problem is derived. The Melnikov analysis is carried out to prove the existence of a complicated nonwandering Cantor set. The dynamical behavior is numerically investigated by means of time history, Poincare map, power spectrum and Lyapunov exponents. Numerical simulations indicate that the onset of chaos is characterized by break of torus as the torque of the magnetic forces is increased. 相似文献
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Alberto Renieri 《Endeavour》1984,8(1):35-43
The generation of coherent synchrotron radiation using beams of relativistic electrons passed through magnetic undulators opens up tremendous scope for photochemistry in general and isotopic separation by laser in particular. Applications for plasma heating in Tokamak-type installations to trigger off the controlled nuclear fusion process are also conceivable. 相似文献
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W.E. Danforth 《Journal of The Franklin Institute》1934,217(3):331-346
We have carried out a geometrical analysis which applies to that type of cosmic ray deflection experiment in which an extended region of magnetic field lies between the lower two of three or more Geiger-Mueller counters arranged in line for counting coincident discharges. It is apparent that charged particles of sufficiently low energy will be deviated away from the last counter and that the counting rate will therefore be reduced by application of the field. This paper presents a method for computing what proportion of electrons of a given energy will be eliminated by application of the field. The method is extended to include a constant loss of energy per unit path length as the particle traverses an iron core. The results of the experiments of Curtiss and of Mott-Smith are interpreted in the light of these calculations. Curtiss' result could be explained if all rays were electrons of 4 × 108 volts energy. One may conclude from his observation that if all the radiation consists of positive or negative electrons, the fraction between 2 × 107 volts and 1.5 × 108 volts is less than 30 per cent. of the total above 2 × 107, and that the fraction between 2 × 107 and 109 is greater than 30 per cent. A comparison of Curtiss' and Mott-Smith's experiments yields no reason for doubting the correctness of using the magnetic induction B when computing the deflection within iron. Nor does it necessarily sustain this procedure. An experiment by W. F. G. Swann and the writer is at present under way for the purpose of securing, if possible, more conclusive evidence on this point. 相似文献
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北京正负电子对撞机升级改造工程 (BEPCII)的直线注入器 (LINAC)要求建立束流轨道的自动校正系统 ,为此对束流轨道偏离的产生原因和轨道校正的方法进行了研究 ,并采用VC 语言编写了相应的校正程序 ,利用最小二乘法原理对束流轨道的校正进行了模拟计算 ,取得了较为理想的结果 相似文献
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为在高能直线加速器出口获得尽可能好的束流品质,严格控制束流在加速器中的轨道是至关重要的。首先定量研究了束流的初始偏轴和加速器部件的安装误差对束流轨道偏轴的影响,并以北京正负电子对撞机二期工程(BEPCII)的直线加速器为例,给出了上述各种误差导致轨道偏轴的模拟计算结果及其分析。进而讨论了BEPCII直线加速器轨道校正系统的设计研究,给出了轨道校正系统的优化布局和对加速器部件的安装公差要求。 相似文献
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The radial and axial motions of electrons in the betatron are described by means of a potential function of forces. Previously reported conditions of equilibrium, stability and damping of oscillations are derived for the region of parabolic variation of the potential. Extension of the analysis to, non-parabolic regions gives an account of the injection in conventional instruments in better agreement with experiment, particularly in regard to higher voltages of injection.Space charge limitations are discussed with the help of the Laplacian of the potential of forces.By means of an additional radial electric field electrons can be introduced as in the magnetron, without any asymmetry inherent in the conventional betatron circumferential injector. The analysis of the conditions of equilibrium and stability, greatly facilitated in this case by the notion of potential, shows that no substantial improvement in space charge limitations can be expected and that the required variations between the flux linking the electron orbits and the magnetic and electric fields at the orbits are difficult to realize on account of their complexity and narrow tolerances. The X-ray output of a small experimental double yoke instrument was measured by a phototube multiplier viewing an irradiated fluorescent screen and gave evidence of multiple group electron capture. 相似文献
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本文简要介绍了开普勒三定律以及确定人造地球卫星在空间瞬时位置的6个轨道参数;详细描述了由美国Celestrak发明并创立的卫星星历即两行轨道数据(two2line orbitalelement)的格式和含义;并根据卫星移动式地面站的特点,开发了一种卫星地面伺服跟踪软件。本软件使用最新的卫星星历,依据两行卫星轨道参数,对伺服系统进行控制,实现对卫星的实时准确跟踪。 相似文献
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This paper studies the problem of robust orbital control for low earth orbit (LEO) spacecraft rendezvous subjects to the parameter uncertainties, the constraints of small-thrust and guaranteed cost during the orbital transfer process. In particular, the rendezvous process is divided into in-plane motion and out-plane motion based on C-W equations, and the relative motion models with parameter uncertainties are established. By considering the property of null controllable with vanishing energy (NCVE), the problem of orbital transfer control with small thrust and bounded control cost is proposed. A new Lyapunov approach is introduced, and the controller design problem is cast into a convex optimization problem subjects to linear matrix inequality (LMI) constraints. With the obtained controller, the orbit transfer process can be accomplished with small thrust and the control cost has an upper bound simultaneously. Different possible initial states of the transfer orbit are also analyzed for the controller design. An illustrative example is provided to show the effectiveness of the proposed control design method, and the different performances caused by different initial states of the transfer orbit are illustrated. 相似文献