振动试验系统在冲击响应谱试验中的应用

随着爆炸冲击环境逐渐受到重视,模拟这种复杂振荡波形的设备也随之增多。文章介绍了在冲击响应谱试验中,振动试验系统的工作原理和使用方法,并对其实用性进行了分析。长期的、大量的试验研究结果表明,使用振动试验系统进行冲击响应谱试验不仅可行,而且还有一定的优势。     

测试理论在紧缩场天线测试中的新应用

文章以中国空间技术研究院紧缩场测试系统的组成和特点为例,分析介绍了紧缩场测试误差的来源、测试设备必要的升级改造和测试软件的更新应用。通过将测试理论知识应用于测试工程实际,可有效去除由于测试场非理想因素引入的各类测试误差,获得更接近天线实际性能的测试结果;同时有效分析处理测试数据,简化实际测试工作,提高测试效率。     

DS/FH扩频测控信号同步方案的捕获性能

针对航天测控信号的高动态以及由载频跳变引起的多普勒频率周期跳变的特点,提出了一种基于快速频率识别和辅助机制的直扩/跳频(DS/FH)混合扩频测控信号的一种同步方案。建立了跳频图案,伪码相位及多普勒频率的三维同步捕获状态转移过程的数学模型,推导出三维捕获的平均捕获时间表达式,及在伪码相位误差、多普勒频移和高斯白噪声条件下的检测概率和虚警概率表达式。仿真分析了在采用时域匹配滤波、频域多通道的直扩捕获方式下,信号和捕获系统参数对三维捕获性能的影响。理论推导与数值仿真结果表明了同步方案的有效性,并为信号设计及捕获系统参数选择提供了理论依据和实际参考。     

基于MIMO技术的卫星高速数据传输系统研究

多输入多输出（MIMO）系统作为提高频谱效率的一种有效方式,已经成为未来无线通信系统实现高速可靠数据传输的突破性技术之一,受到国际众多研究机构的普遍关注。文章通过研究MIMO信道模型、信道容量、卫星信道特征,构建了全新高速数传系统模型,解决了卫星大容量数据实时传输和频带限制之间的矛盾。     

航空发动机振动环境谱统计归纳方法及振动试验台复现

为满足航空发动机及机载产品研制过程贴近使用环境的振动考核试验需求,需根据发动机实测振动数据给出振动考核试验所需的输入谱图。依据GJB/Z 126-99中给出的环境测量数据归纳方法,建立了发动机实测振动环境谱统计归纳方法并通过程序实现。利用发动机多架次实测试飞振动数据统计归纳得到发动机测点位置的振动实测谱。基于能量等效及信号频域特征分布一致原则,将归纳得到的实测谱转化为可用于振动台输入的振动环境谱,并在振动台上进行了振动信号的复现试验。结果表明：振动台输出信号与发动机实测振动信号频域分布特征一致,在统计频率带宽范围内振动总量最大相差5.7%,证明了转化方法是合理的,为航空发动机机载设备贴近使用环境的振动考核试验方法提供了真实的输入谱图。     

New index of long-term variations of galactic cosmic ray intensity

We find that the soft rigidity spectrum of the Galactic Cosmic Ray (GCR) intensity variations for the maximum epoch and the hard rigidity spectrum for the minimum epoch calculated based on the neutron monitors experimental data (1960–2002) are related with the various dependence of the diffusion coefficient on the GCR particle’s rigidity for different epoch of solar activity. This dependence is stronger in the maximum epoch than in the minimum epoch of solar activity, and is provided by the essential temporal rearrangements of the structure of the Interplanetary Magnetic Field (IMF) turbulence from the maxima to minima epoch of solar activity. We also show that the rigidity spectrum of GCR intensity variations is harder for the effective rigidities ∼(10–15) GV (by neutron monitors data), than for the effective rigidities ∼(25–30) GV (by neutron monitors and muon telescopes data). A general scenario of GCR modulation versus solar activity is settled on the essential temporal rearrangements of the structure of the IMF turbulence. Therefore, the temporal changes of the power law rigidity spectrum exponent can be considered as a vital (new) index to explain the 11-year variations of the GCR intensity. We assume that ∼(70–80)% of the changes of the amplitudes of the 11-year variations of GCR intensity is related with the changes of the IMF turbulence versus solar activity.     

Relativistic solar protons in the ground level event of 23 February 1956: New study

In this study we applied again to the outstanding solar particle event of 23 February 1956, the largest one in the entire history of observations of solar cosmic rays. Due to significant improvement of the analysis/modeling techniques and new understanding of physical processes in the solar atmosphere and interplanetary space, a possibility arises to interpret the old data in the light of modern concept of multiple particle acceleration at/near the Sun. In our new analysis the data of available then neutron monitors and muon telescopes are used. The technique of the analysis includes: (a) calculation of asymptotic cones of ground-based detectors; (b) modeling of cosmic ray detector responses at variable parameters of the flux of solar relativistic protons; (c) determination of primary solar proton parameters outside magnetosphere by comparison of computed responses with observations. Certain evidence was obtained that the flux of relativistic solar protons consisted of two distinct components: prompt and delayed ones. The prompt component with exponential energy spectrum caused a giant impulse-like increase at a number of European cosmic ray stations. The delayed component had a power-law spectrum and was a cause of gradual increase at cosmic ray stations in the North American region. A numerical simulation of the proton acceleration in the vicinity of the magnetic reconnection region brings to the proton spectrum with exponential dependence on energy. This agrees with observational data for the prompt component. It is also shown that the huge increase in ∼5000% on neutron monitors was due to the prompt component only with the exponential proton spectrum. The power-law spectrum of comparable intensity gave considerably smaller effect.     

Design and Experiments of Model-free Compound Controller of Flight Simulator

A model-free compound controller design method is proposed to achieve the wide frequency bandwidth requirement of flight simulators. The method based on quantitative feedback theory, acquires system uncertainty under different working conditions through closed-loop identification with power spectrum estimation. Then in controller designing, it makes a tradeoff between the strict requirements for magnitude-frequency characteristics and those for phase-frequency characteristics of flight simulators, by converting the indices of magnitude-frequency characteristics of flight simulators into quantitative feedback theory-based tracking specification bounds and using feedforward controller to attain the required phase-frequency characteristics. Simulation and experimental results indicate that, when used to design inner frame controller of flight simulator, the proposed method can fulfill the requirements for wide frequency bandwidth indices. Compared with other controller design methods, it has the property of model-free and transparency.     

混频电路的应用及分析方法

本通过对混频电路的组成，工作原理及分析，阐明了混频电路的学习和分析方法，结合实用电路，说明了混频电路在电子技术及通信领域的广泛应用。     

地震地面运动功率谱分析中自相关回归法的数学过程研究

本文扼要叙述了用于离散时程数据的功率谱分析的自相关回归法（ARM）的数学过程。本研究进一步确认了赤池氏提出的ARM在地震工程中的适用性。特别是该方法具有由少量随机数据可得稳定、光滑的功率谱密度函数的优点，从而，可以有效地用来研究地震地面运动的非平衡谱特性。本研究的成果对于高层建筑抗震设计有一定的参考价值。