排序方式: 共有23条查询结果,搜索用时 18 毫秒
1.
F. Capitanio A. Bazzano P. Ubertini G. De Cesare M. Del Santo A. Tarana A. Joinet 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2816-2819
On March 2003, IBIS, the γ-ray imager on board the INTEGRAL satellite, detected an outburst from a new source, IGR J17464-3213, that turned out to be an HEAO-1 transient, namely H1743-322. The spectral and temporal evolutions of the source were observed by INTEGRAL in different periods. Also RXTE observed the source for the first time on 2003 March 29 during a PCA Galactic bulge scan. The source flux decayed below the RXTE PCA sensitivity limit in November 2003, then in April 2004 it was again detected by INTEGRAL. On July 3, 2004 the source was again detected by RXTE/PCA at a 2–10 keV intensity of 16 mCrab and on July 7, reached 69 mCrab. Recently, a new outburst was observed on August 2005. We briefly summarise here the behaviour of the source observed by INTEGRAL from March 2003 to August 2005. The new outbursts of the source and the analysis of all the data collected (now public) give a global view of the spectral and time behaviour of this X-ray transient. 相似文献
2.
G. Ghirlanda L. NavaG. Ghisellini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Short and long GRBs are thought to be two distinct classes based on their different duration and spectrum. Through the spectral analysis of two similarly selected samples of BATSE short and long GRBs, we show that short GRBs are harder than long events, confirming what found from the comparison of their hardness ratio. However, this spectral diversity seems to be due to a harder low energy spectral component of short GRBs, rather than a (slightly higher) peak energy. Interestingly short GRBs have a spectrum which is similar to the spectrum of the emission of the first 1–2 s of long events. We find evidence that short GRBs are inconsistent with the Epeak–Eiso correlation defined by long bursts while they follow the same Epeak–Liso correlation of long GRBs. These results, coupled to the similar variability timescale of short events and the first seconds of long ones, suggest that a common (or similar) dissipation mechanism could operate in both classes. The difference in the duration would then be due mainly to the central engine lifetime. 相似文献
3.
为了排除某航空发动机DD6镍基单晶高温合金涡轮转子叶片在室温振动试验中发生的裂纹故障,对故障叶片进行了外观检查、断口分析、表面检查、解剖检查、化学成分分析、金相检查、应力分布计算及热模拟试验,确定了故障叶片裂纹的性质和产生原因.结果表明:涡轮转子叶片裂纹为高周疲劳裂纹,叶片局部区域存在异常的γ'筏排组织是导致该叶片产生早期疲劳开裂的主要原因,且附近区域腐蚀过重及结构上处于应力集中区,也促进了疲劳裂纹的萌生及扩展.针对这些故障,建议优化叶片结构并对腐蚀检查进行严格监控,防止出现γ’筏排组织及腐蚀过重现象,从而避免此类故障再次发生. 相似文献
4.
E.G. Berezhko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(3):429-441
We analyse the results of recent measurements of nonthermal emission from individual supernova remnants (SNRs) and their correspondence to the nonlinear kinetic theory of cosmic ray (CR) acceleration in SNRs. It is shown that the theory fits these data in a satisfactory way and provides the strong evidences for the efficient CR production in SNRs accompanied by significant magnetic field amplification. Magnetic field amplification leads to considerable increase of CR maximum energy so that the spectrum of CRs accelerated in SNRs is consistent with the requirements for the formation of Galactic CR spectrum up to the energy ∼1017 eV. 相似文献
5.
TSIEN Pei-hsin 《中国航空学报》2006,19(Z1)
The changes of DC characteristics of SiGe HBT after being submitted to γ-ray irradiation of 700 krad, 7 000 krad and 10 000 krad were compared to those of Si BJT. Generally speaking, Ib and Ib–Ib0 increase with the doses increasing. For SiGe HBT, with the doses increasing, Ic and Ic–Ic0 as well as the related changes of the current gain (β) will decrease at higher Vbe, while for Si BJT, with the doses increasing, after irradiation, Ib and Ic–Ic0 increase; β and its related changes also decrease with their differences, however, tending to be very small at high doses of 7 000 krad and 10 000 krad. Moreover, given the same doses, the decreases of β are much larger than SiGe HBT, which shows that SiGe HBT’s anti-radiation performance proves to be better than Si BJT. Still, in SiGe HBT, some strange phe-nomena were observed: Ic–Ic0 will increase after the radiation of 7 000 krad in less than 0.65 V and as will β in less than 0.75 V. The mechanism of radiation-induced change in DC characteristics was also discussed. 相似文献
6.
7.
基于γ-Re_(θt)转捩模型的低雷诺数翼型数值分析 总被引:2,自引:0,他引:2
通过综合运用Michel转捩判据和γ-Re_(θt)转捩模型的方法实现对低雷诺数翼型的气动分析。首先通过Michel转捩判据和层流分离位置分别估算转捩动量厚度雷诺数,然后分别用Langtry和Tomac提出的经验关系式计算转捩动量厚度雷诺数和转捩区长度,通过UDF(User-Defined Functions)将不同组的3个经验关联值写入Fluent软件对E387翼型(雷诺数为3×10~5)进行数值分析,并与试验值进行了对比。结果表明:基于Michel转捩判据比基于层流分离更能准确预测转捩位置,基于层流分离预测的转捩位置过于靠前,但是2种方法的气动力计算结果与试验值都比较吻合,Langtry和Tomac的经验关系式计算结果之间差别不大,Tomac方法能够计算出分离泡,且与Selig油流试验吻合较好。 相似文献
8.
应用CFD计算软件ANSYS CFX对水力直径为0.4mm的矩形截面微尺度通道中的气体流动进行了数值模拟.采用了3种流动模型,即γ-Reθt转捩模型、层流模型和剪切应力输运(SST)模型,并将模拟结果与实验结果进行了对比.模拟结果表明:层流模型及SST模型不具有预测转捩的能力;γ-Reθt转捩模型捕捉到了临界雷诺数且摩擦因数相对误差在20%以下.在未达到临界雷诺数之前,通道后部已经出现局部湍流区,且局部湍流区随着雷诺数的增大而增大.壁面摩擦因数的最低点对应的流向位置与通道中前后湍流区的交结位置几乎一致. 相似文献
9.
10.
I.V. Arkhangelskaja A.I. ArkhangelskyYu.D. Kotov P.A. KalmykovA.S. Glyanenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The solar flare of January 20, 2005 (X7.1, 06:36–07:26 UT, maximum at 07:01 UT by the GOES soft X-ray data) was the most powerful one in January 2005 series. The AVS-F apparatus onboard CORONAS-F registered γ-emission during soft X-ray rising phase of this flare in two energy ranges of 0.1–20 MeV and 2–140 MeV. The highest γ-ray energy registered during this flare was ∼140 MeV. Six spectral features were registered in energy spectrum of this solar flare: annihilation + αα (0.4–0.6 MeV), 24Mg + 20Ne + 28Si + neutron capture (1.7–2.3 MeV), 21Ne + 22Ne + 16O + 12С (3.2–5.0 MeV), 16O (5.3–6.9 MeV), one from neutral pions decay (25–110 MeV) and one in energy band 15–21 MeV. Four of them contain typical for solar flares lines – annihilation, nuclear de-excitation and neutron capture at 1H. Spectral feature caused by neutral pions decay was registered during several flares too. Some spectral peculiarities in the region of 15–21 MeV were first observed in solar flare energy spectrum. 相似文献