C/SiC复合材料超声振动钻孔评估

在分析碳纤维增强碳化硅复合材料的力学性能、密度、孔隙率和弯曲强度的基础上 ,进行了超声钻孔工艺试验 ,检测并研究了材料去除率、孔径差、孔边质量和工具损耗情况 ,得出了超声钻孔是一种好的加工方法的结论。     

A Functionally Redundant Altimeter

A scheme to provide redundant sensor data in an automatic control system using the principle of functional redundancy is described. Normally there are three redundant radar altimeters used in the terminal phase of automatic landing of jet transport airplanes. This scheme replaces one of these altimeters with a data processing scheme based on a Kalman filter. The filter is driven by altitude rate and acceleration signals from the air data computer and vertical accelerometer. A special initialization technique employs the two altimeter signals. The feasibility of this scheme is indicated by tests in which data obtained from these several sensors during flight tests are used to drive the functionally redundant altimeter.     

X-Ray spectroscopic investigation of the coronal structure of capella

The binary system Capella (G6 III + F9 III) has been observed on 1979 March 15 and on 1980 March 15–17 with the Objective Grating Spectrometer (OGS) onboard theEinstein Observatory. The spectrum measured with the 1000 l/mm grating covers the range 5–30 Å with a resolution < 1 Å. The spectra show evidence for a bimodal temperature distribution of emission measure in an optically thin plasma with one component 5 million degrees and the other one 10 million degrees. Spectral features can be identified with line emissions from O VIII, Fe XVII, Fe XVIII, Fe XXIV, and Ne X ions. Good spectral fits have been obtained assuming standard cosmic abundances. The data are interpreted in terms of emission from hot static coronal loops rather similar to the magnetic arch structures found on the Sun. It is shown that the conditions required by this model exist on Capella. Mean values of loop parameters are derived for both temperature components.     

The Rosat mission

The primary scientific objective of the ROSAT mission is to perform the first all sky survey with an imaging X-ray telescope leading to an improvement in sensitivity by several orders of magnitude compared with previous surveys. Consequently a large number of new sources (> 10⁵) will be discovered and located with an accuracy of 1 arcmin. After completion of the survey which will take about half a year the instrument will be used for detailed observations of selected targets.The X-ray telescope consists of a fourfold nested Wolter type I mirror system with 80 cm aperture and 240 cm focal length, and three focal plane detectors. In the baseline version these will be imaging proportional counters (0.1 – 2 keV) providing a field of view of 2⁰ × 2⁰.     

Optical observations of the X-ray source 2S0921-630

We report photometric observations of the optical counterpart of the X-ray source 2S0921-630. The data, obtained at the South African Astronomical Observatory during 3 weeks in 1980 and 1981, are consistent with a 17.9 day periodic modulation of the flux in the B band. Correlated variability of the (B-V) and (U-B) colour indices with the B mag. is demonstrated and quantified. The observed B mag. and colours at maximum and minimum light are used to compute some of the system parameters. A model of 2S0921-630 is proposed in terms of a binary system in which the variable inclination of a luminous accretion disc produces the long-term modulation of the optical flux.     

An investigation into the nature of the 4.4 hr periodic source 4U1755-33

We present the results of a continuous 18 hour observation of 4U1755-33 made with the European Space Agency's EXOSAT Observatory. Four 50 min dips in X-ray intensity were observed equally spaced with a period of 4.4 hrs, confirming the periodicity first suggested in White et al. (1984). The dips are spectrally independent. We examine the properties of 4U1755-33 and conclude that the source is most probably point-like and that the metallicity of the absorbing material is at least 600 times less than cosmic values.     

The 3-D Heliosphere from the Ulysses and ACE Solar Wind Ion Composition Experiments

The source region of solar wind plasma is observed to be directly reflected in the compositional pattern of both elemental and charge state compositions. Slow solar wind associated with streamers shows higher freeze-in temperatures and larger FIP enhancements than coronal hole associated wind. Also, the variability of virtually all compositional parameters is much higher for slow solar wind compared to coronal hole associated wind. We show that these compositional patterns persist even though stream-stream interactions complicate the identification based on in situ plasma parameters. This revised version was published online in August 2006 with corrections to the Cover Date.     

喷管潜入段二维两相冷流实验

建立了喷管潜入段二维两相冷流实验设备,进行了相应的实验。实验清晰地显示了在潜入喷管进口背壁凹区旋涡的产生、稳定、消失,以及粒子的冲刷、粘贴、脱落、沉积等反复作用的复杂现象,它们与流动的雷诺数、粒子的含量和尺寸、潜入喷管进口处的形状和潜入深度、背壁型面等因素有关。     

Characteristics of Icy Surfaces

The surfaces of the Solar System’s icy satellites show an extraordinary variety of morphological features, which bear witness to exchange processes between the surface and subsurface. In this paper we review the characteristics of surface features on the moons of Jupiter, Saturn, Uranus and Neptune. Using data from spacecraft missions, we discuss the detailed morphology, size, and topography of cryovolcanic, tectonic, aeolian, fluvial, and impact features of both large moons and smaller satellites.     

高纯α—Fe热压缩动态复原机制的研究

用高纯α-Fe在GLEEBLE-1500热模拟机上率进行了热压缩试验。变形温度分别为550℃,700℃,800℃和900℃,应变速率分别为0.001s~(-1),0.01s~(-1),0.1s~(-1),1s~(-1)和10s~(-1)。对其热压缩过程中的显微结构变化及真应力-真应变曲线进行的研究结果表明,形变温度的增加和应变速率降低有利于动态再结晶的进行;对动态再结晶与Z参数关系的研究结果表明,在一定的Z参数范围内即25<1nZ<37,高纯α-Fe可以发生动态再结晶,并给出动态再结晶图。