共查询到20条相似文献,搜索用时 78 毫秒
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所谓"双转动"物体是指相对于转动参考系仍然做转动的物体.关于牵连加速求解的问题,在高中物理竞赛中常有涉及,但是对于相对转动参考系转动的物体加速度求解,学生容易犯的最大错误,就是混淆加速度的牵连关系和参考系的转换关系,于是在不同参考系中迷失了解决问题的方向.笔者从一 相似文献
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当物体相对于转动参照系存在相对运动时,对于转动参照系,物体除了受到惯性离心力作用外,还会受到科里奥利力的作用,我们利用磁性显示板显示运动轨迹的方法直观而且清楚地演示了这一力学现象。 相似文献
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测物体转动拨量,验证转动定律是普物实验的基本内容.目前测转动馈量的仪器已有几种:如三线摆、扭摆和塔轮型转动实验仪;1984年南开大学物理系谭成章教授等设计、研制成功新型转动仪器——气垫转盘.笔者根据教学使用情况,对上述三线摆和气垫转盘作了一点比较研究,现分述如下:一、直观教学效果比较出物体转动保量是这个实验的基本内容,验证转动定律、平行轴定理都要通过出转动惯量I的值进行验证.测I值的方法有几种,笔者认为直接用转动定律I一M/卢的测量方法最简捷,实验教学效果最好.这是因为,按定义转动惯量是物体保持原有转… 相似文献
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讨论高速运动物体几种形象之间的联系与区别,指出物体做Terrell转动后的形象并非表现形象,并且在特定条件下,高速运动物体的洛仑兹收缩图象是可以看到的. 相似文献
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在大学物理教学中,关于圆盘状物体的物理量有很多,如电学中带电圆环、带电圆盘,其周围空间产生的电场强度和电势怎样计算?关于铜质圆盘状物体在磁场中转动时产生的电动势的计算问题等;力学中圆盘的转动惯量、椭圆盘的转动惯量,圆盘状物体转动时的摩擦力矩问题、驱动力做功问题等.本文将对这些物理量进行分析,并找出一些共同的规律和特点,将其归纳总结,计算所需要的物理量. 相似文献
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以两个质点组成的杆连接体绕固定转动轴转动问题为例,定量推证了在质心参考系中一个物体相对于另一个物体运动的动能等于两个物体相对于系统质心运动的动能之和的结论,并对两道经典试题给出多种解答方法. 相似文献
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A circular planar object can be levitated with several hundreds of microns by ultrasonic near-field acoustic levitation (NFAL). However, when both the sound source and the levitated object are circularly shaped and the center of the levitated object does not coincide with the source center, instability problem often occurs. When this happens, it becomes difficult to pick up or transport the object for the next process. In this study, when the center of the levitated object was offset from the source center, the moving direction of the levitated object was predicted by using the time averaged potential around the levitated object. The wobbling frequency of the levitated object was calculated by analyzing the nonlinear wobbling motion of the object. It was shown that the predicted wobbling frequencies agreed with measured ones well. Finally, a safe zone was suggested to avoid the unstable movement of an object. 相似文献
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Yu. A. Novikov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(6):1283-1288
The effect of the inclination of a test object on the calibration of a scanning electron microscope (SEM) is considered. It is shown that when the step of a structure or the size of the upper and lower bases of the ledges and grooves is used as a certified parameter, the inclination of the test object does not affect the calibration of the SEM. When using the value of the projection of the inclined sidewall of ledges and grooves on the structure base, the incline of the test object leads to a systematic error in determining the increase (pixel size) several times greater than the random error. A method for determining the inclination angle of the test object is developed that enables the measurement of this angle and the identification and elimination of a systematic error. 相似文献
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把正方体切成无数平行断面,每个断面均有一个光锥,在无数个光锥内观察断面截面与投影截面及断面和断面投影的变化,可得出以下结论:(1)X线影像变形是光锥作用的结果;(2)无论物体投影面是否成角,光锥中心线直射或斜射作用不变;(3)各断面截面的椭圆离心率反映物体空间歪斜程度,是真正的变形因素;(4)投影截面椭圆离心率分别大于、等于或小于断面截面椭圆离心率,则断面正中纵径投影/实长分别大于、等于或小于通过该投影中点的横径投影/实长;(5)若物体投影面成角,将会产生断面投影不均等放大现象;(6)变形程度与物体厚度成正比,且变形的程度与点光源至物体的距离成逆向变化,而与物体投影面距离无关;(7)教材中的论述是错误的。 相似文献
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QIN Yuwen GE BaozhenCHEN Ximing ZHANG Yimol JIAN Shuisheng 《Chinese Journal of Lasers》1997,6(2):122-130
l.IntroductionJointtransformcorrelation[1]hasbeeninvestigatedwidelyinrecentyears[2~4]be-causeitsreferenceimagesandobjectimagescanbeuPdatedinreal-time[5J.Nonlinearjointtransformcorre1ationtheoretica1ana1ysis[']showsthatcomparedwiththelinearjointtransformcorrelation,non1inearjointtransformcorrelationcanproducemorehighautcacorre1ationPeakintensity,andthelargerPeaktosideloberatiothataregoodforelectronicdevicestodetectandana]yze.Onthebasisofthemodu1ationprincipleana1ysisoftheliq-uidcrysta11ightva… 相似文献
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Pui Sum Yuen 《Optik》2014
The binary object treated is a square with a square hole. We first use a set of initial phases to determine the symmetry of the object. The initial image has the gross shape of a square with a square hole, and preserves symmetry of the object. With another set of initial phases, the initial image has gross shape of a square with a hole. Sayre's equation is applied to refine this gross shape. After iterations, the result shows a square with a distorted square hole. These three squares have approximately same edge lengths. These squares are larger than the object. The holes are smaller than the hole of the object. The initial phases or the gross shapes can be used as starting phases or starting envelopes in other iterative algorithms. 相似文献
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D. A. Balakin A. V. Belinsky A. S. Chirkin 《Journal of Experimental and Theoretical Physics》2017,125(2):210-222
Ghost imaging allows one to obtain information on an object from the spatial correlation function between photons propagating through or reflected from the object and photons of the reference arm. In this case, detection in the object arm is performed over the entire aperture of the beam and, therefore, it does not give information on the object. The reference beam does not interact with the object, but is recorded with a scanning point detector or a CCD array permitting the measurement of the spatial correlation function of photons in two arms. The use of multimode entangled quantum light beams by illuminating the object by one beam and orienting other beams to reference arms makes it possible to obtain simultaneously several ghost images (GIs). Cross correlations of multiplexed GIs (MGIs) are determined by eighth-order field correlation functions. A special algorithm is developed for calculating higher-order correlations of Bose operators. The presence of GI cross correlations is used for improving the quality of the reconstructed object’s image by their processing using the measurement reduction method. An example of the computer simulation of the image reconstruction by MGIs formed in the field of four-frequency entangled quantum states is considered. It is found that in this case the reduced GI has a signal-to-noise ratio several times higher than that of GIs. 相似文献
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Determination of the shape of a binary object by means of chosen initial phases and Sayre's equation
Pui Sum Yuen 《Optik》2014
The binary object treated is a square. We first use a set of initial phases to determine the symmetry of the object. The result shows a well-shaped image, and preserves symmetry of the object. We then use another set of initial phases. The result has gross shape of a square with approximately correct dimensions. Sayre's equation is applied to refine the gross shape. After iterations, the result shows an image which is close to a square with sharp boundary and has approximately correct dimensions. The charge densities of the image are approximately evenly distributed, scattering about the value of 1, and has no negative charge density. The shape of the binary object is obtained. The initial phases or the gross shape can be used as starting phases or starting envelope in other iterative algorithms. 相似文献
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为了在天基远距离条件下反演三轴稳定空间目标表面的光学特性参数,提出了基于可见光时序光度信号分析的光学特性宏观表征模型的反演重构方法.首先,综合考虑空间目标的结构特性、表面材料特性、帆板的对日指向运动特性、光照观测几何以及光学系统特性,完善了面向在轨观测的空间目标可见光时序光度建模方法;其次,将光度模型等效为双面模型,并利用双向反射分布函数(BRDF)的多级融合模型表征复杂材料表面的光学反射特性,将BRDF对应的面积反射率乘积作为待反演参数;最后,以时序光度信号的测量值与模型值之间的差异最小为优化目标,建立线性优化方法,实现模型参数的反演.仿真实验表明,提出的模型在轨重构方法对于近轨观测条件下的本体、帆板信号的重构精度达到97%以上,验证了方法的正确性. 相似文献
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Zampolli M Tesei A Canepa G Godin OA 《The Journal of the Acoustical Society of America》2008,123(6):4051-4058
A numerically efficient technique is presented for computing the field radiated or scattered from three-dimensional objects embedded within layered acoustic media. The distance between the receivers and the object of interest is supposed to be large compared to the acoustic wavelength. The method requires the pressure and normal particle displacement on the surface of the object or on an arbitrary circumscribing surface, as an input, together with a knowledge of the layered medium Green's functions. The numerical integration of the full wave number spectral representation of the Green's functions is avoided by employing approximate formulas which are available in terms of elementary functions. The pressure and normal particle displacement on the surface of the object of interest, on the other hand, may be known by analytical or numerical means or from experiments. No restrictions are placed on the location of the object, which may lie above, below, or across the interface between the fluid media. The proposed technique is verified through numerical examples, for which the near field pressure and the particle displacement are computed via a finite-element method. The results are compared to validated reference models, which are based on the full wave number spectral integral Green's function. 相似文献