Open clusters in dense fields: the importance of field-star decontamination for NGC 5715, Lyngå 4, Lyngå 9, Trumpler 23, Trumpler 26 and Czernik 37     

C. Bonatto  E. Bica 《Monthly notices of the Royal Astronomical Society》2007,377(3):1301-1323

  相似文献   

WEP的安全技术分析及AES的解决方案     

谢荣清  郝玉洁 《成都信息工程学院学报》2006,21(1):38-42

在深入分析IEEE 802.11标准的有线等价私密（WEP）安全漏洞的基础上,提出了用高级加密算法AES代替RC4,AES提供了比RC4更高的加密性能和更加强大的安全保护,因此AES方案必将成为新一代的加密标准.  相似文献   

基于BF533的基4 FFT算法的DSP实现     

史贤勇  陈子为 《成都信息工程学院学报》2006,21(Z1):43-47

首先介绍了基4时域抽取FFT算法的快速高效的原理及实现方法, 然后用MATLAB对该算法进行了仿真,分析了对其优化的几个方向,并提出了一种利用单一倒序表进行多点数位倒序的新方法.最后给出了在ADSP-BF533 DSP 上采用C语言实现FFT 的软件设计方法,并在ADSP-BF533 KZ-KIT LiteTM评估板上成功实现,经过实验验证, 结果正确,各项指标均达到了设计要求.该实现方法具有可移植性好、速度快等优点,具有很好的参考价值和应用前景.  相似文献   

Vertical Migrations and Feeding Rhythms of Acartia clausi and Pseudodiaptomus hessei (Copepoda: Calanoida) in a Tropical Lagoon (Ebrié, Côte d'Ivoire)     

Acartia clausi 《Estuarine, Coastal and Shelf Science》2001,52(6):715

Diel changes in vertical distribution and gut pigment contents of Acartia clausi andPseudodiaptomus hessei were studied during several 24-h time series performed between 1993 and 1997 in four sites of the Ebrié Lagoon (Côte d'Ivoire). The sites differed by their morphology and their hydrological structure and by the vertical distribution of chlorophyll biomass. Both species showed classical diel vertical migrations (DVM). Copepodites and adult stages of P. hessei were almost benthic during the day and evenly distributed through the water column at night. The amplitude of DVM of A. clausi increased from copepodites I–III to adults. Copepodites and adults of A. clausi increased significantly their gut fluorescence at night, whereas those of P. hessei showed no clear diel feeding rhythm (DFR). These results suggest that A. clausi feed mostly at night on phytoplanktonic particles and P. hessei feed mostly on benthic algal particles during the day and on sestonic particles at night. No relationship was observed between DFR and DVM because both patterns occurred when food was either vertically homogeneous or vertically stratified. The daily average gut fluorescence of A. clausi increased with ambient chlorophyll concentration until around 12–15 μg l⁻¹, whereas no relationship was found for P. hessei. The implication of these patterns on the adaptation capacities and the behaviour of the two species are discussed. The DVM of P. hessei should explain its rarity in the estuarine area. The comparison of our results with previous ones suggests an evolution of A. clausi DFR between 1981–1982 and 1996–1997, in relation to an intensification of eutrophication.  相似文献   

Orbital parameters of the high‐mass X‐ray binary 4U 2206+54     

K. A. Stoyanov  R. K. Zamanov  G. Y. Latev  A. Y. Abedin  N. A. Tomov 《Astronomische Nachrichten》2014,335(10):1060-1063

We present new radial velocities of the high‐mass X‐ray binary star 4U 2206+54 based on optical spectra obtained with the Coudé spectrograph at the 2 m RCC telescope of the Rozhen National Astronomical Observatory, Bulgaria in the period November 2011–July 2013. The radial velocity curve of the He I δ6678 Å line is modeled with an orbital period P_orb = 9.568 d and an eccentricity of e = 0.3. These new measurements of the radial velocity resolve the disagreements of the orbital period discussions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4C 21.35的γ射线光变特征及其与射电光变的相关性     

王钧陶  白金明  刘洪涛  王放  廖能惠  范绪亮 《天文学进展》2014,(4)

利用从2008年8月5日到2013年10月23日Fermi-LAT的观测数据,对4C 21.35的100 MeV到300 GeV的γ射线数据进行了分析,总结了1天bin情况下的光变特征,并在3小时bin的基础上详细研究了所选的11个大的爆发,得到了5.4 h的最短光变时标。先用对射电光变曲线减去一个线性增长,再通过相关分析得到100 MeVE300 GeV的γ射线光变领先于15 GHz射电光变351.2_(38.0)~(13.8)d,并用γ射线辐射区对于射电辐射是光学厚对其加以解释,从而在辐射区匀速运动的假设下得到,这样的时延对应着γ射线辐射区到射电光学薄区域的距离为△r≈44.4 pc。通过与VLBA观测得到的15 GHz射电核的半径相比较,得到辐射区向外运动过程中可能存在减速的结论。  相似文献   

Discussing the physical meaning of the absorption feature at 2.1 keV in 4U 1538–52     

J. J. Rodes‐Roca  J. M. Torrejn  S. Martínez‐Nuez  A. Gimnez‐García  G. Bernabu 《Astronomische Nachrichten》2014,335(8):804-811

High resolution X‐ray spectroscopy is a powerful tool for studying the nature of the matter surrounding the neutron star in X‐ray binaries and its interaction between the stellar wind and the compact object. In particular, absorption features in their spectra could reveal the presence of atmospheres of the neutron star or their magnetic field strength. Here we present an investigation of the absorption feature at 2.1 keV in the X‐ray spectrum of the high mass X‐ray binary 4U 1538–52 based on our previous analysis of the XMM‐Newton data. We study various possible origins and discuss the different physical scenarios in order to explain this feature. A likely interpretation is that the feature is associated with atomic transitions in an O/Ne neutron star atmosphere or of hydrogen and helium like Fe or Si ions formed in the stellar wind of the donor. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

南京一次持续性浓雾天气过程的边界层特征及水汽来源分析   总被引：1，自引：0，他引：1  

张礼春  朱彬  耿慧  马国忠 《气象》2013,39(10):1284-1292

本文选取2006年12月24—27日（平流辐射雾）南京大雾的外场观测资料及NCEP的2.5°×2.5° NC再分析资料和GDAS全球1°×1°气象资料,结合天气形势、气象要素、物理量场,并利用轨迹分析方法,对这次浓雾的边界层特征及水汽输送进行分析,探讨这次浓雾形成和持续的主要边界层物理和天气学成因。分析表明：（1）这次浓雾过程期间始终存在深厚的逆温层结,甚至出现多层逆温。浓雾过程中,在中上空不同逆温层顶温度比地面温度高出2~5℃。逆温层厚多在200 m以上,26日08时逆温层厚达500 m。逆温层的存在,使大气层结更加稳定,在雾形成前期利于低层水汽聚集,雾形成后又抑制水汽的扩散,利于雾体的发展和维持,是这次浓雾能持续约64 h,强浓雾时段（能见度＜50 m）持续约37 h的重要因素。（2）这次平流雾过程低层水汽通量散度呈负值,上空持续出现水汽辐合,最强水汽辐合出现在25日02时左右,为-30×10-7 g·s-1·cm-2·hPa-1。低层辐合利于水汽的聚集,雾得以形成和发展,而雾过程后期水汽辐散则加快雾的消亡。贯穿整个雾过程的水汽辐合是这次平流辐射雾长时间维持的重要条件。（3）这次平流辐射雾过程中水汽输送路径是自中国东部沿海抵达南京;雾期间,水汽又来自海上源源不断的输送,最大时南京上空水汽通量达到2 g·s-1·hPa-1·cm-1。水汽的供应和后期补充量,决定了浓雾的持续时间。  相似文献   

Economic consequences of the US withdrawal from the Kyoto/Bonn Protocol     

《Climate Policy》2013,13(4):273-292

Abstract

The US decision not to ratify the Kyoto Protocol and the recent outcomes of the Bonn and Marrakech Conferences of the Parties have important implications for both the effectiveness and the efficiency of future climate policies. Among these implications, those related with technical change and with the functioning of the international market for carbon emissions are particularly relevant, because these variables have the largest impact on the overall abatement cost to be borne by Annex B countries in the short and in the long run. This paper analyses the consequences of the US decision to withdraw from the Kyoto/Bonn Protocol both on technological innovation and on the price of emission permits (and, as a consequence, on abatement costs). In particular, the analysis highlights mechanisms and feedbacks related to technological innovation, technological spillovers and R&D which could be relevant and which modify some policy relevant conclusions. First, we identify two feedback effects which explain why our results lead to a less significant fall in the price of permits than in most empirical analyses recently circulated. We show that the US defection from the Kyoto Protocol, by inducing a decline in the demand and price of emission permits, lowers the incentives to undertake energy-saving R&D. As a consequence, emissions increase and feed back on the demand and supply of permits, thus implying a lower decline in the price of permits than previously estimated. At the same time, as a result of the reduced R&D investments and the augmented emissions, climate change damages intensify and require an increase in investments that are again coupled with a growth of emissions. By thus again increasing the demand for permits and reducing their supply, this effect enhances the previous mechanism. Notwithstanding the lower decline in the price of permits, the paper still identifies a smaller price than would occur with a US participation. Therefore, we emphasise in a second step the crucial role of Russia in climate negotiations due to a large increase in Russia's bargaining power.  相似文献   

Changes of Terrestrial Water Storage in River Basins of China Projected by RegCM4          下载免费PDF全文

ZOU Jing  XIE Zheng-Hui  QIN Pei-Hu  MA Qian  SUN Qin 《大气和海洋科学快报》2013,6(3):154-160

In this study, a historic simulation covering the period from 1951 to 2000 and three projected scenario simulations covering 2001-2050 were conducted employing the regional climate model RegCM4 to detect the changes of terrestrial water storage (TWS) in major river basins of China, using the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES): A1B, A2, and B1. The historic simulation revealed that the variations of TWS, which are dominated by precipitation in the basins, rely highly on their climatic features. Compared with the historic simulation, the changes of TWS in the scenario simulations showed strong regional differences. However, for all scenarios, TWS was found to increase most in Northeast China and surrounding mountains around the Tibetan Plateau, and decrease most in eastern regions of China. Unlike the low seasonal variations of TWS in arid areas, the TWS showed strong seasonal variations in eastern monsoon areas, with the maximum changes usually occurring in summer, when TWS increases most in a year. Among the three scenario simulations, TWS increased most in Songhua River Basin of B1 scenario, and de- creased most in Pearl River Basin of A2 scenario and Hai River Basin of A1B scenario, accompanied by different annual trends and seasonal variations.  相似文献