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介绍了基于几何莫尔条纹原理和衍射干涉原理的两种光栅精密位移测量系统及各自的特点。综述了国内外对光栅干涉式精密位移测量系统的研究进展,总结了系统存在的关键问题及发展趋势。光栅干涉式精密位移测量系统的优点是对环境要求小,测量分辨率和精度较高,结构紧凑,成本低。该系统需要解决的问题包括提高光栅以及光学元器件制造和安装精度;寻求一种更高精度的检测手段对光栅位移测量系统进行标定等。光栅干涉式精密位移测量系统的发展方向为更高测量分辨率和精度,大量程、多维度测量以及尺寸小巧。该系统在现代工业加工精密制造领域将具有更广阔的应用前景。 相似文献
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为提高飞行器电气控制系统测量和管理的可靠性,实现电气控制系统的综合管理;通过采用ARINC659背板总线、冗余的电气控制系统模块化设计方法,设计并实现了一种电气控制系统。这篇文章介绍了该系统的主要功能、技术特点、硬件和软件设计。该系统在满足实时性、可靠性需求的同时,具有快速的系统重构和很强的可配置性,而且大大减少了飞机电气系统的重量,适应电气控制系统综合控制发展的方向。基于659总线的飞行器电气控制系统,解决了复杂机电系统的数据融合和综合管理,在工程实践中已成功应用。 相似文献
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为了解决四旋翼飞行器模型阶次较高的问题,对悬停状态下四旋翼飞行器的特征模型进行了研究;首先,分析建立了四旋翼飞行器的动力学模型,并利用小扰动原理对模型进行简化,得到飞行器的特征模型结构;进而,搭建飞行器辨识实验平台,获得可靠的输入输出数据;最后,为了保证飞行器初始阶段稳定性,选择适合的参数初值,并通过模型拟合度选择在线递推算法,建立了飞行器的特征模型;通过对实验结果的分析,表明了所建特征模型的有效性。 相似文献
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基于气浮轴承的自由滚转实验技术是测量再入飞行器小不对称滚转气动力的重要方法.文章研究中对偏翼标模进行了小滚转力矩测量,并针对实验系统的特点,对气浮轴承进行了无风实验标定和真空实验标定,给出了其动态特性结果.进一步分析了气浮轴承动态特性、原始数据采集测量误差和参数辨识误差对实验结果的影响,并给出了综合误差分析结果,说明了主要误差来源.结果显示:滚转力矩系数和滚转阻尼导数测量综合误差分别约为10-7和10-4量级,实验中可根据实际情况进行误差处理.研究结果对气浮轴承自由滚转实验精度提高、方案设计和设备研制等具有重要的实际意义. 相似文献
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四旋翼无人飞行器姿态数据采集处理系统 总被引:1,自引:0,他引:1
针对机械振动等因素产生的噪声对加速度传感器测量姿态数据的影响,增加了陀螺仪并运用卡尔曼滤波对加速度传感器和陀螺仪的数据进行融合处理;与以往均值和中值等滤波姿态算法相比,采用卡尔曼滤波算法能够获得可靠、稳定的姿态数据,为四旋翼无人飞行器稳定飞行提供有效保障;介绍了姿态传感器和采集处理系统硬件结构及软件实现,运用图形化编程语言LabView实现对四旋翼无人飞行器实时姿态曲线显示、姿态数据存储、回放等功能;经测试,能有效的降低机械振动等噪声对飞行器姿态测量的影响,提高姿态数据估计的精度,达到了预期的目标。 相似文献
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G. E. Dobretsov T. I. Syrejshchikova Yu. A. Gryzunov M. N. Yakimenko 《Journal of fluorescence》1998,8(1):27-34
In heterogeneous media, including biological objects, fluorescent molecules of one kind often exist as a mixture of species
with different fluorescence parameters. Fractional concentrations of these species can be measured by analyzing their fluorescence
decay amplitudes. The amplitudes are linear functions of concentrations of actually fluorescent molecules, i.e., molecules
whose fluorescence decay can be measured. Other (quenched) molecules do not influence these amplitudes. The other parameter
that has to be measured to calculate these concentrations is the radiative rate constant. The parameter can be excluded by
comparison of decay amplitudes of the sample studied and a standard. The comparison should be made taking into account the
dependence of the radiation rates on emision wavelength. The method has been tested in experiments with the fluorescent probe
3-methoxybenzanthrone (MBA) bound with phosphatidylcholine bilayer membranes. The probe has a complex fluorescence decay in
these membranes. The decay can be described as two exponentials, with decay times of 2 and 12 ns and a blue-shifted fluorescence
spectrum of the short-life component as compared with long-life one. The shift was used to correct calculated radiative rate
values. After this, about 100% of the MBA molecules were found to be fluorescent in these membranes. Thus, this approach can
be used to measure absolute concentrations of subpopulations of fluorescent molecules in heterogeneous biological objects. 相似文献
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Virendra Kumar Yuhua Gu Satrajit Basu Anders Berglund Steven A. Eschrich Matthew B. Schabath Kenneth Forster Hugo J.W.L. Aerts Andre Dekker David Fenstermacher Dmitry B. Goldgof Lawrence O. Hall Philippe Lambin Yoganand Balagurunathan Robert A. Gatenby Robert J. Gillies 《Magnetic resonance imaging》2012
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在WDM全光网络上构建上层网络需要考虑上层网络的保护机制.上层网络按保护机制可分为最大故障链路数保护网和连通保护网.针对它们的不同特点给出了构建两类上层网络并使费用最低的启发式路由算法.与已有方法相比,具有算法简单,时间复杂性小,容易实用化的特点.大量的模拟计算也证明了算法的正确性. 相似文献
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高能强子一强子反应实验中发现一系列引人注目的自旋效应,这些效应出现的机理一直是人们关注的热门课题之一.近几年,在实验及理论家共同的努力下,虽仍有许多不清楚的问题,但已取得一些突破.结果表明,不仅对这些现象产生机理研究能为强子结构及强子反应机制提供信息,而且这些现象本身也用作探索强子反应机制的工具.例如用它们来研究小xB光子与强子反应的性质.本报告将首先简单总结这些现象及其产生机理研究的结论,然后介绍该例的主要思想及结果. 相似文献
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MRI in cerebral developmental malformations and epilepsy 总被引:2,自引:0,他引:2
Ruben I. Kuzniecky 《Magnetic resonance imaging》1995,13(8):1137-1145
Cerebral developmental malformations are increasingly recognized as a major cause of developmental delay and epilepsy. The incidence of these developmental malformations in patients with epilepsy is not known, but epilepsy surgery data suggest that this pathology is commonly seen in children who undergo epilepsy surgery for intractable epilepsy. These malformations can be diagnosed by a combination of clinical, neurophysiological, and imaging techniques. However, imaging techniques such as MRI have been able to provide in vivo recognition of many of these malformations and have contributed to the recognition of specific syndromes. These malformations can be classified on an anatomical basis either into diffuse, unilateral, or generalized. However, a combination of imaging data in conjunction with genetics and embryology may be more appropriate in the future. Further technical developments promise to increase the sensitivity of MRI in detecting these malformations and may help to delineate the possible biology of these disorders. 相似文献
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In the framework of an ESA project, a microbiological experiment in space is planned. In this experiment a cell culture will be exposed to cosmic radiation onboard a spacecraft. Because the living cell culture will be directly on a nuclear track detector stack, this detector will be submitted to a different environment than normally used. The temperature will be 37°C and the culture will be in a biological growth medium. Tests have been conducted to assess the possible use of PADC in these conditions. For this, a series of alpha irradiated detectors have been exposed for different periods of time (up to 1 month) to these ‘biological’ conditions. The radiological properties as well as the mechanical properties (swelling…) have been investigated. Results show no influence of the biological environment on the PADC, which makes it useable under these circumstances. 相似文献
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Henning Knutsen 《General Relativity and Gravitation》1991,23(7):843-859
We extend a method by Goldman to include conditions which are both necessary and sufficient for construction of physically acceptable relativistic fluid spheres. We thus give the conditions for having finite and non-negative pressure and finite and positive density inside the fluid sphere. We also give conditions for the pressure gradient and the density gradient to be negative and for the speed of sound to be less than the speed of light in vacuum. We further give the condition for the trace of the energy-momentum tensor to be positive and for the relativistic adiabatic index to be larger than 4/3. A model given by Goldman is examined, and we find that all these conditions are fulfilled. We further show that this model is stable. However, we also give a class ofnew exact solutions, and show that these models are physically valied. These models are also stable with respect to small radial disturbances. We calculated the total mass, the density and the physical radius for these fluid spheres. Some of these spheres turn out to be extremely compact. They can have a radius of only several centimeters, but typically contain the mass of a planet. We put these models forward as tentative exact solutions for spheres which could contain the hidden dark matter in the universe. 相似文献
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Double differences of masses can be used to isolate specific nucleonic interactions. With the new 2003 mass tabulation a significant increase in the number of empirical average proton-neutron interactions of the last nucleons can be extracted. It is shown that they exhibit dramatic and distinctive patterns, especially near doubly magic nuclei, that these patterns can be interpreted with a simple ansatz based on overlaps of proton and neutron orbits, and that the trends in p-n interactions across entire shells can be understood if they are correlated with the fractional shell filling. It is shown how these empirical interactions can be sensitive to changes in shell structure in exotic nuclei. Finally, these results are used to suggest criteria for future mass measurements with new exotic beam facilities. 相似文献
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Recent studies have shown that in certain cases, cardiac and respiratory rate fluctuations in BOLD-weighted MRI time courses may be an artifact unique to rapid sampled acquisitions and may not be present in longer repetition-time acquisitions. The implication of this is that, in these cases, cardiac and respiratory rate fluctuations are not aliased into data that undersample these effects and do not affect the resulting time course measurements. In this study, we show that these cases are specific to regions of large cerebrospinal fluid content and are not generally true for gray matter regions of the brain. We demonstrate that in many brain regions of interest, these fluctuations are directly observed as BOLD fluctuations and thus will affect measurements that undersample these effects. 相似文献
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J.P.Briand 《中国物理 C》2007,31(Z1):236-236
The ECR ion sources have mainly been used until now for injection of cyclotrons and a large number of these sources are presently in operation through the world.Most cyclotrons are used today for nuclear physics researches but an increasing number of these accelerators are now devoted to medical applications.The ECR ion sources have also been extensively used for producing low energy beams for academic researches in atomic and surface physics.These studies led to very encouraging results opening the way to industrial applications. In this talk some of the most promising applications of HCI beams will be reviewed.The development of these applications will require some important improvements of the ECR sources which will be discussed.A special emphasis will be given to the respective roles of ECR and EBIS ion sources in these industrial applications, and some economic and market considerations discussed. 相似文献