Spectroscopic Constraints on Models of Ion-cyclotron Resonance Heating in the Polar Solar Corona

Using empirical velocity distributions derived from UVCS and SUMER ultraviolet spectroscopy, we construct theoretical models of anisotropic ion temperatures in the polar solar corona. The primary energy deposition mechanism we investigate is the dissipation of high frequency (10-10000 Hz) ion-cyclotron resonant Alfvén waves which can heat and accelerate ions differently depending on their charge and mass. We find that it is possible to explain the observed high perpendicular temperatures and strong anisotropies with relatively small amplitudes for the resonant waves. There is suggestive evidence for steepening of the Alfvén wave spectrum between the coronal base and the largest heights observed spectroscopically. Because the ion-cyclotron wave dissipation is rapid, even for minor ions like O⁵⁺, the observed extended heating seems to demand a constantly replenished population of waves over several solar radii. This indicates that the waves are generated gradually throughout the wind rather than propagated up from the base of the corona. This revised version was published online in June 2006 with corrections to the Cover Date.     

用衰减全反射(ATR)研究金属薄膜的物理性质

本文作者所设计的实验是利用光学中全反射衰减特性方法测量在介质上蒸镀的金属薄膜的厚度和各种频率下的复介电常数等物理性质，它可以精确测定１００～１０００范围内金属膜层的厚度和ε（ω）值，以及一些其它性质，是研究固体表面物理的一种有效的方法和技术。     

一种新型正弦压力发生器

介绍了一种利用压电叠堆激励管道内液体介质发生谐振产生正弦压力的发生装置.与其它正弦压力发生器相比,本装置压力源的激励方式新颖,工作频率较高,所产生的正弦压力波的幅值较大,失真度较小.     

Alfvénic Electron Acceleration in Aurora Occurs in Global Alfvén Resonosphere Region

Auroral emission caused by electron precipitation (Hardy et al., 1987, J. Geophys. Res. 92, 12275–12294) is powered by magnetospheric driving processes. It is not yet fully understood how the energy transfer mechanisms are responsible for the electron precipitation. It has been proposed (Hasegawa, 1976, J. Geophys. Res. 81, 5083–5090) that Alfvén waves coming from the magnetosphere play some role in powering the aurora (Wygant et al., 2000, J. Geophys. Res. 105, 18675–18692, Keiling et al., 2003, Science 299, 383–386). Alfvén-wave-induced electron acceleration is shown to be confined in a rather narrow radial distance range of 4–5 R _E (Earth radii) and its importance, relative to other electron acceleration mechanisms, depends strongly on the magnetic disturbance level so that it represents 10% of all electron precipitation power during quiet conditions and increased to 40% during disturbed conditions. Our observations suggest that an electron Landau resonance mechanism operating in the “Alfvén resonosphere” is responsible for the energy transfer.     

基于起落架参数设计的某直升机地面共振及参数影响分析

建立了某直升机地面共振分析力学模型,计算了起落架在桨毂中心处的等效刚度和阻尼,针对某直升机进行了地面共振分析,同时分析了摆振铰外伸量、质量静距、桨毂中心有效刚度等对地面共振的影响,为避免地面共振及参数改进提供依据。     

直升机旋翼与机体耦合的空中与地面共振稳定性分析

直升机旋翼气动机械稳定性的一个重要方面是空中与地面稳定性问题。本文从旋翼桨叶的结构型式、气动模型和分析方法几个方面对直升机空中与地面稳定性研究进行了回顾与展望。在简单分析方法的基础上 ,也对更精确的分析方法进行探讨     

两端固定输流管道在脉动内流作用下参数共振的最优控制

采用压电片作为控制执行元件,对两端固定输流管道在脉动流作用下的参数共振进行了最优控制.基于二次型性能指标最优控制原理,针对离散后的运动方程在零平衡点附近Jacobian矩阵的非时变部分设计了最优控制器.最后,通过数值仿真的方法对控制方案的有效性进行了验证.结果表明,该方案对输流管道在第一、第二振型次谐波共振区域及组合共振区域的参数共振的控制均有很好的效果.     

矩形微波谐振腔单模谐振条件

本文首次推导出矩形微波谐振腔的单膜谐振于TE101模的条件。所给出的结论以于单模矩形谐振腔的工程设计具有非常重要的指导意义。     

直升机尾桨/尾梁耦合稳定性分析研究

单桨带尾桨直升机的尾旋翼设计成摆振柔软型后,带来了新的动力学问题:尾桨与尾梁耦合动不稳定性问题。本文简述了它与主旋翼/机体耦合动不稳定问题的差别,主要介绍了尾桨与尾梁耦合动不稳定性问题的分析方法,通过算例分析,为消除这种不稳定性,对一些关键设计参数提出了设计要求。     

相位检测误差对核磁共振陀螺输出频率的影响

针对核磁共振陀螺中采用相位检测方案时可能引起额外频率误差的问题,提出了通过控制电子顺磁共振失谐量及静磁场扰动来抑制额外频率误差的方案。基于Bloch方程,推导了惰性气体原子系综输出频率的表达式,并将相位检测的过程包含在内。建立了考虑相位检测误差的核磁共振陀螺频率误差方程,给出了相位检测引入的额外频率误差表达式并进行了数值仿真。仿真结果表明,通过设定合适的共振失谐量,其额外频率误差至少可以抑制1个数量级,而通过精确地抑制静磁场的一阶及二阶扰动,可以进一步抑制1～3个数量级,将额外频率误差降低到nHz量级。