On the Differences in Composition between Solar Energetic Particles and Solar Wind

Although the average composition of solar energetic particles (SEPs) and the bulk solar wind are similar in a number of ways, there are key differences which imply that solar wind is not the principal seed population for SEPs accelerated by coronal mass ejection (CME) driven shocks. This paper reviews these composition differences and considers the composition of other possible seed populations, including coronal material, impulsive flare material, and interplanetary CME material.     

Variability of spectra in large solar energeticparticle events

Using data from the Solar Isotope Spectrometer on the Advanced Composition Explorer obtained during 36large solar energetic particle events (SEPs) that occurred during 1997–2002 we have examined the spectral characteristics of oxygen and iron. Based on the shape of the oxygen spectrum during the decay phase following the peak in particle intensity, each SEP event was categorized as either exponential (7 events) or power law (29 events). We find that the exponential events were typically the larger events (in terms of peak oxygen intensity) and had Fe/0 ratios that strongly decreased with increasing energy.Event-averaged Fe/0 ratios (integrated over 12 to 60 MeV/nucleon) were at or below coronal abundances for nearly all these events, while the ratios obtained in the power law events were typically enhanced over coronal values. The majority of the power law events had the same spectral index for both 0 and Fe resulting in an Fe/0 ratio independent of energy. However 6 of the 29 power law events had Fe/0 ratios that increased with increasing energy due to an Fe spectral index less negative than that of 0. We consider simple diffusion theory in an effort to understand the nature of these events and obtain preliminary but promising results.     

基于弹流润滑转子-滚动轴承系统碰摩-不对中耦合故障的动力学分析

研究弹流润滑(EHL)转子-滚动轴承系统在碰摩-不对中耦合故障状态下的动力学响应.基于EHL理论与Hertz弹性接触理论,并考虑转静碰摩故障与转子不对中故障,建立耦合故障作用下转子-滚动轴承系统非线性动力学微分方程,通过龙格库塔数值解法进行求解得到故障状态下系统振动响应,对比分析其结果并在航空发动机转子实验台进行验证.研究结果表明:①考虑EHL理论对单一碰摩故障系统的影响较大.考虑EHL理论的系统进入拟周期运动与周期2运动状态时的转速较未考虑EHL理论系统明显提高,周期2解所处的转速区间较未考虑EHL理论系统大.②考虑EHL理论对碰摩-不对中耦合故障系统的影响较大.考虑EHL理论的系统由周期1解进入拟周期运动,且进入拟周期状态时的转速较未考虑EHL理论的系统明显提高.③通过计算结果与实验结果进行对比分析,可发现考虑EHL理论的耦合故障系统的转子在1/2倍频与2倍频处的振动响应均弱于未考虑EHL理论的系统,考虑EHL理论的模型比未考虑EHL理论的模型能更准确体现耦合故障系统的振动响应.     

某型航空发动机空中起动供油规律的研究

研究某型航空发动机空中起动困难问题,现有自动起动器没有考虑飞行高度对供油规律的影响,发动机在空中起动时存在富油状态.分析了影响起动供油规律的因素,在现有自动起动器结构基础上,设计了高空修正模块来补偿飞行高度对供油规律的影响.建立了自动起动器的数学模型,对改进的自动起动器进行了仿真分析和试验.仿真结果和试验验证了改进方案的可行性,与地面起动相比,空中起动的供油量随着飞行高度的增加而降低.采用改进的空中起动供油规律可补偿飞行高度对供油特性的影响,解决发动机空中起动时的富油状态问题.      

The Low-Energy Telescope (LET) and SEP Central Electronics for the STEREO Mission

The Low-Energy Telescope (LET) is one of four sensors that make up the Solar Energetic Particle (SEP) instrument of the IMPACT investigation for NASA’s STEREO mission. The LET is designed to measure the elemental composition, energy spectra, angular distributions, and arrival times of H to Ni ions over the energy range from ～3 to ～30 MeV/nucleon. It will also identify the rare isotope ³He and trans-iron nuclei with 30≤Z≤83. The SEP measurements from the two STEREO spacecraft will be combined with data from ACE and other 1-AU spacecraft to provide multipoint investigations of the energetic particles that result from interplanetary shocks driven by coronal mass ejections (CMEs) and from solar flare events. The multipoint in situ observations of SEPs and solar-wind plasma will complement STEREO images of CMEs in order to investigate their role in space weather. Each LET instrument includes a sensor system made up of an array of 14 solid-state detectors composed of 54 segments that are individually analyzed by custom Pulse Height Analysis System Integrated Circuits (PHASICs). The signals from four PHASIC chips in each LET are used by a Minimal Instruction Set Computer (MISC) to provide onboard particle identification of a dozen species in ～12 energy intervals at event rates of ～1,000 events/sec. An additional control unit, called SEP Central, gathers data from the four SEP sensors, controls the SEP bias supply, and manages the interfaces to the sensors and the SEP interface to the Instrument Data Processing Unit (IDPU). This article outlines the scientific objectives that LET will address, describes the design and operation of LET and the SEP Central electronics, and discusses the data products that will result.     

分布式光纤传感技术及其在航空航天领域的应用展望

综述了分布式布里渊和瑞利光纤传感技术的主要技术原理、特点及发展概况,包括布里渊光时域分析技术、布里渊相关域分析技术、动态布里渊光纤传感技术、瑞利光时域反射计技术和光频域反射计技术五项主要技术。在此基础上,对分布式光纤传感技术在航空领域的应用进行了回顾,并对其在航天领域的可能应用进行了探讨。     

一种复合材料翼梁后屈曲计算方法

基于金属结构的张力场理论,考虑复合材料的特点,适当地引入假设,提出了一种复合材料翼梁的后屈曲计算方法,并与4mm左右中等厚度腹板的复合材料翼梁试验结果进行对比。结果表明,该方法可以较为准确的预测复合材料翼梁进入张力场后的应力分布和翼梁的破坏载荷,弥补了复合材料翼梁后屈曲计算方法的缺失。     

发动机连杆的保守模糊可靠度设计

从强度安全性的角度出发,综合运用概率密度函数联合积分法与功能密度函数积分法,整理并推导了发动机连杆的保守模糊可靠度计算公式,即应力、强度及构件的几何尺寸等参数都为正态分布,隶属度函数为k次抛物线分布时的模糊可靠度计算公式;通过VB编程实现发动机连杆保守模糊可靠度设计数值解的计算.本程序可直接应用于设计计算中,以提高连杆的设计水平.