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测量杨氏模量的方法很多,如静态拉伸法、梁的弯曲法等.通常当采用静态拉伸法测量金属丝做小的伸长量时,应用了光杠杆的放大原理.测量装置如图1所示. 相似文献
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1 光杠杆法测量中主要误差的分析 光杠杆法是高等学校基础实验的微小长度测量中经常采用的主要方法之一,此方法不论在设计思想上,还是在测量技能综合训练方面,都是很有意义的,它的优越之处还在于把微小长度变化量δ通过光杠杆放大为竖尺刻度的变化量△a=a′-a2D/bδ(这里D为光杠杆镜面到竖尺的距离,b为光杠杆后足尖到二前足尖连线的垂直距离). 相似文献
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针对实验室常见的液体体胀系数测量方法操作繁琐、劳动强度大、测定时间长、实验费用高等缺点,设计了光杠杆测量液体体胀系数的实验装置,使装入试管中的液体温度缓慢变化,通过光杠杆测量液面的高度的变化,可以准确地测量出液体的体胀系数。 相似文献
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针对实验室常见的液体体胀系数测量方法操作繁琐、劳动强度大、测定时间长、实验费用高等缺点,设计了光杠杆测量液体体胀系数的实验装置,使装入试管中的液体温度缓慢变化,通过光杠杆测量液面的高度的变化,可以准确地测量出液体的体胀系数。 相似文献
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大空间精密测量在重大装备制造、空间科技、国防工业等方面发挥着重要作用,激光高精度绝对长度测量是大空间精密测量领域的重要研究课题.调频连续波激光测距是近年来激光绝对测距研究的热点,它克服了脉冲法测量分辨率低和相位法激光测距存在2π缠绕模糊度问题的缺点,有着测量精度高、量程大的优点.本文研究了调频连续波激光测距的原理,分析了影响其测距分辨率的主要原因,证明了利用等光频间隔采样来抑制激光调制非线性对测距结果影响的可行性.该方法可以提高测距分辨率,且系统构成简单、实用性强.搭建了光纤调频连续波激光测距系统,并加入了辅助干涉光路对测量信号进行等光频间隔采样.利用该系统进行了测距分辨率实验,实验结果表明,本系统测量分辨率可以达到50μm,测量范围达到了10m. 相似文献
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在地面、海面、天空复杂背景下对红外小目标稳定跟踪是亟需解决的难题。为兼顾鲁棒性和实时性,以判别尺度空间跟踪算法为基础,应用可有效表征目标区域灰度突变特性和目标形状信息的广义结构张量算法作为特征提取方法。改进后的算法更适用于红外图像快速处理,能提高跟踪鲁棒性,且计算量小、效率高,目标特征维度低。为提高跟踪稳定性,依据置信度决定跟踪模型更新,避免模型被错误样本干扰。与判别尺度空间跟踪算法相比,所研究算法在准确性、实时性、鲁棒性方面均具有显著优势,且实现300 fps的跟踪速度@256×256像素图像。 相似文献
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Moving small target detection under complex background in infrared image sequence is one of the major challenges of modern military in Early Warning Systems (EWS) and the use of Long-Range Strike (LRS). However, because of the low SNR and undulating background, the infrared moving small target detection is a difficult problem in a long time. To solve this problem, a novel spatial–temporal detection method based on bi-dimensional empirical mode decomposition (EMD) and time-domain difference is proposed in this paper. This method is downright self-data decomposition and do not rely on any transition kernel function, so it has a strong adaptive capacity. Firstly, we generalized the 1D EMD algorithm to the 2D case. In this process, the project has solved serial issues in 2D EMD, such as large amount of data operations, define and identify extrema in 2D case, and two-dimensional signal boundary corrosion. The EMD algorithm studied in this project can be well adapted to the automatic detection of small targets under low SNR and complex background. Secondly, considering the characteristics of moving target, we proposed an improved filtering method based on three-frame difference on basis of the original difference filtering in time-domain, which greatly improves the ability of anti-jamming algorithm. Finally, we proposed a new time–space fusion method based on a combined processing of 2D EMD and improved time-domain differential filtering. And, experimental results show that this method works well in infrared small moving target detection under low SNR and complex background. 相似文献
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A. Macor F. Doveil C. Chandre G. Ciraolo R. Lima M. Vittot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):519-530
A numerical and experimental study of a control method
aimed at channeling chaos by building barriers in phase space is
performed on a paradigm for wave-particle interaction, i.e., a
traveling wave tube. Control of chaotic diffusion is achieved by
adding small apt modifications to the system with a low additional
cost of energy. This modification is realized experimentally
through additional waves with small amplitudes. Robustness of the
method is investigated both numerically and experimentally.
An erratum to this article is available at . 相似文献
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The method of sequential perturbations is applied to find the uncertainty in estimated surface temperature and heat flux from a two-dimensional analytical inverse heat conduction problem related to impinging jet quenching experiments. It is shown that for meaningful uncertainty estimates, the inverse solution itself must be formulated such that it can be interpreted as giving average surface conditions over a small period of time and space. A procedure for estimating the time and space resolution limits of the solution is proposed. 相似文献
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Large inflatable structures have been the subject of renewed interest for scientists/engineers in recent years due to their potential space applications such as communication antennas, solar thermal propulsion and space solar power. The major advantages of using inflatable structures in space are their extremely low-weight, on-orbit deployability and inherent low launch volume. An inflated torus is a key component of many inflated space structures such as a thin membrane reflector. In view of their importance, structural static and dynamic behavior of inflated torus need to be investigated. In order to develop a more realistic model, dynamic interaction between the enclosed fluid and the torus has been included in the present work. An appreciable decrease in the modal frequencies is observed when fluid–structure interaction is taken into account. Some additional modes are also obtained. It is concluded that fluid–structure interaction significantly affects the dynamic behavior of inflatable space structures. 相似文献
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One of room acoustic goals, especially in small to medium rooms, is sound diffusion in low frequencies, which have been the
subject of lots of researches. Sound diffusion is a very important consideration in acoustics because it minimizes the coherent
reflections that cause problems. It also tends to make an enclosed space sound larger than it is. Diffusion is an excellent
alternative or complement to sound absorption in acoustic treatment because it doesn’t really remove much energy, which means
it can be used to effectively reduce reflections while still leaving an ambient or live sounding space. Distribution of diffusive
and nondiffusive surfaces on room walls affect sound diffusion in room, but the amount, combination, and location of these
surfaces are still the matter of question. This paper investigates effects of these issues on room acoustic frequency response
in different parts of the room with different source-receiver locations. Room acoustic model based on wave method is used
(implemented) which is very accurate and convenient for low frequencies in such rooms. Different distributions of acoustic
surfaces on room walls have been introduced to the model and room frequency response results are calculated. For the purpose
of comparison, some measurements results are presented. Finally for more smooth frequency response in small and medium rooms,
some suggestions are made. 相似文献
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基于外部光注入的光泵浦自旋垂直腔表面发射激光器(vertical cavity surface-emitting laser,VCSEL)的两个混沌偏振分量,提出了对两个复杂形状目标中的多区域精确测距方案.这里,两个混沌偏振探测波具有飞秒量级快速动态并且被双极性sinc波形调制,使它们具有时空不相关特性.利用这些特性,通过计算多束延时反馈混沌偏振探测波形和与之相对应的参考波形的相关性,实现了对两个复杂形状目标多区域位置矢量精确测量.研究结果表明,对多区域小目标的测距具有非常低的相对误差(低于0.94%).当光电探测器的带宽足够大时,其测距的分辨率达到0.4 mm,并具有很强的抗噪声能力.本文的研究结果在复杂形状目标的精确测距方面具有潜在应用. 相似文献