碳纤维增强树脂基复合材料中激光脉冲能量对超声L波的影响

利用不同激光脉冲与碳纤维树脂基复合材料相互作用产生的瞬态热效应激发超声纵波(L波),分析激光脉冲能量对L波的影响.试验结果表明,激励声波的幅度直接与脉冲的能量相关,在高能量区的纵波幅度明显比在低能量区的大,缺陷的存在明显影响L波的存在和幅度.     

Changes in the amino acid code.

The genetic code is characterized by a pattern arising from "wobble-pairing" between codons and anticodons, so that one nucleotide in the first anticodon position can pair with more than one nucleotide in the third position of a codon. Earlier codes may have existed in which there were fewer anticodons than at present, so that these earlier codes contained fewer amino acids. The universal code was formerly thought to be the only currently existing code used by terrestrial species. It is now known that differences exist from the universal code in mitochondrial coding systems, and also that mitochondrial systems differ from each other. These findings lend support to the proposal that archetypal codes preceded the present universal code. Such archetypal codes may have had some resemblances to mitochondrial codes.     

The image/poetry education and public outreach program

Education and public outreach are viewed by NASA as significant undertakings for all of its space missions. The IMAGE satellite is one of the first missions to explicitly include `E&PO in its original proposal to NASA in 1996. We will discuss what IMAGE has accomplished in this area to date, and what new activities it will conduct following a successful launch.     

试建立基于检测振动加速度信号的设备故障部位诊断模型

往复式压缩机、内燃机等复杂设备,一旦出现故障,诊断的首要任务是要判断它们的故障部位。以检测振动加速度信号取代传统的耳听手摸的经验方法是这类设备诊断的一个趋势。尝试着提出了基于检测振动加速度信号的设备故障部位诊断模型--单特征模型和多特征集成模型。通过在往复式压缩机和内燃机上的实例验证表明,提出的单特征模型和多特征集成模型具有一定的可行性,其中多特征集成模型比单特征模型更有效。     

Subjective vertical before and after space flight

Three scientist astronauts on the D1 spacelab mission participated in a series of orientation experiments before and after exposure to orbital weightlessness. Each subject was tilted about a roll axis at 15 deg intervals up to +/-90 deg. At each angle the subject set a luminous line to what he perceived to be the vertical. The results of these tests are presented.     

民用飞机舱门飞行锁机构接触力计算分析

研究飞机飞行锁机构中的接触力对于民用飞机飞行锁机构的设计具有重要意义。首先介绍飞行锁机构的功能和主要设计依据,阐明某民用飞机飞行锁机构的工作原理,并对其传力路径进行分析;然后采用工程算法、多刚体模型和多柔体模型三种计算方法计算飞行锁工作时曲柄与飞行锁摇臂之间的接触力;最后对三种计算方法进行对比,分析不同方法计算得到的接触力力值产生差异的原因。结果表明:多刚体模型计算值与工程算法计算值产生差异的主要原因是机构空行程导致的力臂变化,多柔体模型计算值与多刚体模型计算值产生差异的原因主要是受力过程中的结构变形。     

Ionospheric response of equatorial and low latitude F-region during the intense geomagnetic storm on 24–25 August 2005

In this investigation, we present and discuss the response of the ionospheric F-region in the South American and East Asian sectors during an intense geomagnetic storm in August 2005. The geomagnetic storm studied reached a minimum Dst of −216 nT at 12:00 UT on 24 August. In this work ionospheric sounding data obtained of 24, 25, and 26 August 2005 at Palmas (PAL; 10.2° S, 48.2° W; dip latitude 6.6° S), São José dos Campos (SJC, 23.2° S, 45.9° W; dip latitude 17.6° S), Brazil, Ho Chi Minh City, (HCM; 10.5° N, 106.3° E; dip latitude 2.9° N), Vietnam, Okinawa (OKI; 26.3° N, 127.8° E; dip latitude 21.2° N), Japan, are presented. Also, the GPS observations obtained at different stations in the equatorial and low-latitude regions in the Brazilian sector are presented. On the night of 24–25 August 2005, the h′F variations show traveling ionospheric disturbances associated with Joule heating in the auroral zone from SJC to PAL. The foF2 variations show a positive storm phase on the night of 24–25 August at PAL and SJC during the recovery phase. Also, the GPS-VTEC observations at several stations in the Brazilian sector show a fairly similar positive storm phase on 24 August. During the fast decrease of Dst (between 10:00 and 11:00 UT) on 24 August, there is a prompt penetration of electric field of magnetospheric origin that result in abrupt increase (∼12:00 UT) in foF2 at PAL, SJC (Brazil) and OKI (Japan) and in VTEC at IMPZ, BOMJ, PARA and SMAR (Brazil). OKI showed strong oscillations of the F-region on the night 24 August resulted to the propagation of traveling atmospheric disturbances (TADs) by Joule heating in the auroral region. These effects result a strong positive observed at OKI station. During the daytime on 25 August, in the recovery phase, the foF2 observations showed positive ionospheric storm at HCM station. Some differences in the latitudinal response of the F-region is also observed in the South American and East Asian sectors.     

超音速燃烧室燃烧效率数学模型及气流状态参数的计算

本文分析及提出了超音速燃烧冲压发动机燃烧室燃烧效率的数学模型.该模型综合了氢气喷射方式、燃烧室进口气流参数以及燃烧室结构的影响因素.用这一数学模型求解一组一元流方程.计算出通过燃烧室的气流状态参数,计算结果与试验数据对比,证明这个模型是适用的.     

喷雾运动初始条件问题的研究

根据所完成的流动环境中颗粒在初始区域内速度分布的测量结果，对颗粒运动初始条件的问题进行了全面的研究，提出了统计性，随机性和确定性的三种初始条件及其数学处理方法，在此基础上，应用喷雾两相流的数值方法，计算了喷雾的运动，比较了不同初始条件对计算结果的影响，并将所得计算结果与实验结果做了比较，两者符合较好。     

基于空基伪卫星的双星定位系统增强方案

针对"北斗"双星定位系统不能实现无源定位和精度不能满足用户需求的问题,提出了空基伪卫星增强双星定位系统的方案并研究了其中的关键技术难点——星座布局、空基伪卫星自身定位及系统时间同步问题。研究结果表明,空基伪卫星不仅可以增强双星系统实现三维无源定位,而且具有覆盖范围大、星座布局好等特点,具有广阔的应用前景。