振动环境试验力参数测量技术研究

目前美欧航天界在航天器振动环境试验中,已将采用力限制控制技术形成一项技术标准,主要目的是减少试验中造成过试验的几率,我国航天部门也开始针对此项技术进行应用研究。在力限制控制技术中如何保证力参数测量的实施和准确性是进行此项研究的关键技术之一,文中主要介绍在此项研究中多分量力参数测量的实施过程,及测量的数据结果和数据分析,目的是对振动试验环境使用测力单元进行力参数测量技术进行一次总结,为进一步开展力参数测量技术的研究积累经验。

A Brief Report of Graphic Explanations for Generalized Potential Temperature in the Non-Uniformly Saturated Atmosphere

Compared to potential temperature （θ） in the dry atmosphere and equivalent potential temperature （θc） in the saturated atmosphere, generalized potential tem- perature （θ＂） has already proven a better thermodynamic parameter in describing the non-uniformly saturated real atmosphere. To add otherwise absent graphic explanations, this paper first presents the physical definition of θ through a tephigram. Then, the utility of the measurement in identifying and forecasting the locations of precipita- tion maxima and heat wave areas with diagnostic com- parison studies and traditionally used thermodynamic parameters is shown.

Modeling and parameter identification of amplitude- and frequency-dependent rubber isolator

A model to describe the hysteresis damping characteristic of rubber material was presented.It consists of a parallel spring and damper,whose coefficients change with the vibration amplitude and frequency.In order to acquire these relations,force decomposition was carried out according to some sine vibration measurement data of nonlinear forces changing with the deformation of the rubber material.The nonlinear force is decomposed into a spring force and a damper force,which are represented by the amplitude-and frequency-dependent spring and damper coefficients,respectively.Repeating this step for different measurements gives different coefficients corresponding to different amplitudes and frequencies.Then,the application of a parameter identification method provides the requested approximation functions over amplitude and frequency.Using those formulae,as an example,the dynamic characteristic of a hollow shaft system supported by rubber rings was analyzed and the acceleration response curve in the centroid position was calculated.Comparisons with the sine vibration experiments of the real system show a maximal inaccuracy of 8.5%.Application of this model and procedure can simplify the modeling and analysis of mechanical systems including rubber materials.

Accurate vision measurement for kinematic parameters of satellite separation tests

The accurate measurement of kinematic parameters in satellite separation tests has great significance in evaluating separation performance. A novel study is made on the measuring accuracy of monocular and binocular, which are the two main vision measurement methods used for kinematic parameters. As satellite separation process is transient and high-dynamic, it will bring more extraction errors to the binocular. Based on the design approach of intersection measure and variance ratio, the monocular method reflects higher precision, simpler structure and easier calibration for level satellite separation. In ground separation tests, a high-speed monocular system is developed to gain and analyze twelve kinematic parameters of a small satellite. Research shows that this monocular method can be widely applied for its high precision, with position accuracy of 0.5 mm, speed accuracy of 5 mm/s, and angular velocity accuracy of 1 (°)/s.

Measuring the kinetic parameters of saltating sand grains using a high-speed digital camera

A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains.The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport.Moreover,the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory,and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.

Theoretical study on cross sensitivity of fiber Bragg grating sensor affected by double and triple external variables

In this work, the theoretical model of FBG when it is affected by double external variables (temperature and transverse pressure) and triple external variables (temperature, axial strain and transverse pressure) is deduced, respectively. The simulated results show that the properties of cross sensitivity would change in a certain regulation with the external effects and fiber parameters. At the same time, some valuable suggestions about how to improve the measurement accuracy are put forward as well.

Operation methods of resistive random access memory

In this paper, different electrical measurement and operation methods of resistive random access memory （RRAM） have been summarized, including voltage sweeping mode （VSM）, current sweeping mode （CSM）, co lstant current stress （CCS）, constant voltage stress （CVS）, rectangular pulse mode （RPM）, and triangle pulse mode （TPM）. Meanwhile, the effects of these meas- urement methods on the forming, set, reset and read operation as well as endurance performance have been compared. Finally, their respective controllability of various resistive switching parameters have been summar zeal and analyzed.

Distinguish on the viability of human umbilical cord mesenchymal stem cells using delayed luminescence

In this paper, we report the discrimination of the viability of human umbilical cord mesenchymal stem cells(hUC-MSCs) with photo-induced delayed luminescence(DL). We measure the DL decay kinetics of hUC-MSCs using an ultraweak luminescence detection system, and find the significant difference in the weight distributions of the decay rate for hUC-MSCs with high and low viabilities. Spectral discrimination of hUC-MSCs with high and low viabilities is thus carried out by comparing the DL kinetics parameters, including the initial intensity, the peak decay rate and the peak weight value. Our results show that the novel optical method for the viability diagnosis of hUC-MSCs has a promising prospect.