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The fastest pulsar and the slowest nova; the oldest galaxies and the youngest stars; the weirdest life forms and the commonest
dwarfs; the highest energy particles and the lowest energy photons. These were some of the extremes of Astrophysics 2006.
We attempt also to bring you updates on things of which there is currently only one (habitable planets, the Sun, and the Universe)
and others of which there are always many, like meteors and molecules, black holes and binaries. 相似文献
2.
吴波%张翥%沈剑韵%彭德林%柳松清 《宇航材料工艺》2002,32(2):47-50
讨论了Ti2AlNb基合金的熔炼特点,概括介绍了真空水冷铜坩埚感应凝壳熔炼的设备结构原理和工艺技术,结合Ti2AlNb基合金的熔炼实践,研究了合金元素的加入形式、熔炼室真空度对合金铸锭的均匀性以及合金中Al挥发烧损的影响规律。结果表明:采用水冷铜坩埚真空感应凝壳熔炼Ti2AlNb基合金,合金铸锭成分均匀性很好,随着熔炼工艺的不同,Al挥发烧损在5%~10%(质量分数)之间。 相似文献
3.
J. L. Linsky 《Space Science Reviews》2007,130(1-4):367-375
Analysis of UV spectra obtained with the HST, FUSE and other satellites provides a new understanding of the deuterium abundance
in the local region of the galactic disk. The wide range of gas-phase D/H measurements obtained outside of the Local Bubble
can now be explained as due to different amounts of deuterium depletion on carbonaceous grains. The total D/H ratio including
deuterium in the gas and dust phases is at least 23 parts per million of hydrogen, which is providing a challenge to models
of galactic chemical evolution. Analysis of HST and ground-based spectra of many lines of sight to stars within the Local
Bubble have identified interstellar velocity components that are consistent with more than 15 velocity vectors. We have identified
the structures of 15 nearby warm interstellar clouds on the basis of these velocity vectors and common temperatures and depletions.
We estimate the distances and masses of these clouds and compare their locations with cold interstellar clouds. 相似文献
4.
P. C. Frisch 《Space Science Reviews》2007,130(1-4):355-365
The properties of interstellar matter at the Sun are regulated by our location with respect to a void in the local matter
distribution, known as the Local Bubble. The Local Bubble (LB) is bounded by associations of massive stars and fossil supernovae
that have disrupted dense interstellar matter (ISM), driving low density intermediate velocity ISM into the void. The Sun
appears to be located in one of these flows of low density material. This nearby interstellar matter, dubbed the Local Fluff,
has a bulk velocity of ∼19 km s−1 in the local standard of rest. The flow is coming from the direction of the gas and dust ring formed where the Loop I supernova
remnant merges into the LB. Optical polarization data suggest that the local interstellar magnetic field lines are draped
over the heliosphere. A longstanding discrepancy between the high thermal pressure of plasma filling the LB and low thermal
pressures in the embedded Local Fluff cloudlets is partially mitigated when the ram pressure component parallel to the cloudlet
flow direction is included. 相似文献
5.
Aya Bamba Hiroya Yamaguchi Katsuji Koyama Junko S. Hiraga Steve Holt John P. Hughes Hideaki Katagiri Jun Kataoka Satoru Katsuda Shunji Kitamoto Motohide Kokubun Hironori Matsumoto Emi Miyata Koji Mori Hiroshi Nakajima Masanobu Ozaki Rob Petre Akiko Sekiguchi Tadayuki Takahashi Takaaki Tanaka Yukikatsu Terada Hiroshi Tomida Yohko Tsuboi Masahiro Tsujimoto Hiroshi Tsunemi Yasunobu Uchiyama Masaru Ueno Shin Watanabe 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(3):411-415
SN 1006 is one of the supernova remnants (SNRs) with relatively low-temperature electrons, considering the young age of just 1000 years. We carried out SN 1006 mapping observations with the X-ray Imaging Spectrometers (XIS) and the Hard X-ray Detector (HXD) onboard Suzaku, the fifth Japanese X-ray satellite. Thanks to the excellent spectral resolution of XIS in the soft X-ray band, H-like and He-like oxygen emission lines were clearly detected, and we could make a map of the line intensity, and as well as a flux and the photon index of nonthermal component. We found that these parameters have spatial dependences from region to region in the SNR; the north region is bright in nonthermal, while dim in thermal; the east region is bright in both nonthermal and thermal; the inner region shows dim nonthermal and bright thermal emission. The photon index is the smallest in the north region. 相似文献
6.
H.J. Völk E.G. Berezhko L.T. Ksenofontov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(3):473-476
For the case of Tycho’s supernova remnant (SNR), we present the relation between the blast wave and contact discontinuity radii calculated within the nonlinear kinetic theory of cosmic ray (CR) acceleration in SNRs. It is demonstrated that these radii are confirmed by recently published Chandra measurements which show that the observed contact discontinuity radius is very close to the shock radius. Therefore a consistent explanation of these observations can be given in terms of efficient CR acceleration which makes the medium more compressible. 相似文献
7.
Examination of the spatial distribution of CO intensity of Comet Halley indicates that a large fraction of CO originates from
the refractory organic component in the coma, rather than directly from the volatiles in the nucleus. Based on the fluffy
aggregate interstellar dust comet model, we have estimated the upper limits of the total amount of CO provided by coma dust.
The implications from the comparison of the predicted results with the observed value have been discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(5):1503-1517
The increased number of potential threat modes under multi-constellation advanced receiver autonomy integrity monitoring (ARAIM) requires an increase in the number of subsets and a correspondingly high computational load. A new satellite selection method based on integrity support message (ISM) parameters is proposed and compared with GDOP-based selection. The performance was tested on five days of data measurements from 21 multi-global navigation satellite system experiment (MGEX) stations distributed around the world, as well as simulation using the broadcast ephemeris. The results show that the proposed ISM-based satellite selection method is highly compatible with the baseline ARAIM. This method could reduce the computational times by about 60–70% quickly, with minimising vertical protection level (VPL) loss, which was consistently within 1 m, even a reduced VPL value in some epochs, and resulting in an improved availability. The simulation results were similar to the MGEX data. It appears that the application of ISM-based satellite selection can effectively reduce computational burden with a minimal impact on availability. 相似文献