The stellar mass spectrum of the open cluster NGC 3293     

Robert W. Slawson  Zoran Ninkov  Elliott P. Horch 《Astrophysics and Space Science》2007,312(3-4):171-187

We have obtained and analyzed UBVRI CCD frames of the young, 4–10 Myr, open cluster NGC 3293 and the surrounding field in order to study its stellar content and determine the cluster’s IMF. We found significantly fewer lower mass stars, M≤2.5M _⊙, than expected. This is particularly so if a single age for the cluster of 4.6 Myr is adopted as derived from fitting evolutionary models to the upper main sequence. Some intermediate-mass stars near the main sequence in the HR diagram imply an age for the cluster of about 10 Myr. When compared with the Scalo (The stellar initial mass function. ASP conference series, vol. 24, p. 201, 1998) IMF scaled to the cluster IMF in the intermediate mass range, 2.5≤M/M _⊙≤8.0 where there is good agreement, the high mass stars have a distinctly flatter IMF, indicating an over abundance of these stars, and there is a sharp turnover in the distribution at lower masses. The radial density distribution of cluster stars in the massive and intermediate mass regimes indicate that these stars are more concentrated to the cluster core whereas the lower-mass stars show little concentration. We suggest that this is evidence supporting the formation of massive stars through accretion and/or coagulation processes in denser cluster cores at the expense of the lower mass proto-stars. R.W. Slawson and E.P. Horch are guest investigators at the University of Toronto Southern Observatory, Las Campanas, Chile.  相似文献   

Late Tertiary tectonic evolution of northern Iran: A case for simple crustal folding     

Bernard Guest  Alice Guest  Gary Axen   《Global and Planetary Change》2007,58(1-4):435

Here we present a crustal folding or buckling mechanism to explain the rootless 3–5 km high Alborz Mountains in northern Iran as well as  10 km of Late Miocene to recent subsidence in the south Caspian basin and  3–6 km of subsidence in the central Iranian basin in the context of the middle Miocene to recent Arabia–Eurasia collision. A key element of the mechanism is the presence of lateral and vertical lithospheric strength contrasts between the north Iranian continental and south Caspian oceanic crusts: when compression from the collision is applied across the region, the strong south Caspian oceanic crust, buried under > 10 km of premiddle Miocene sediment, interacts with the bottom of the mechanically strong continental upper crust of northern Iran, resulting in upward buckling of the continental crust and downward buckling of the oceanic crust. We test this mechanism using a finite-element numerical model with a Maxwell rheology and obtain results that are consistent with the geological and geophysical observations. The observations compiled here and the model results demonstrate the potential for using this region as a natural laboratory for studying the early stages of continent–oceanic collision, including processes like basin inversion, fault localization and, potentially, subduction initiation.  相似文献   

高轨空间碎片的观测模拟     

杨远贵  冯和生  郭锐  张云成 《天文研究与技术》2004,1(1):69-74

对高轨空间碎片进行了观测模拟。在观测模拟中，分别选取南京和云南两个观测站；采用2种跟踪方式：跟踪恒星和跟踪卫星；对于同一地理经度上的同步卫星进行了观测；提供了发现新目标的方法；并给出了新目标的初轨。这为我国空间碎片的数据库的建立作了有益的尝试，对于卫星和航天器的飞行安全具有特别重要的意义。  相似文献   

Solution of the propagation of the waves in open channels by the transfer matrix method     

R. Daneshfaraz  B. Kaya   《Ocean Engineering》2008,35(11-12):1075-1079

Many problems in mechanics can be solved by the use of the transfer matrix method. The use of this method in hydraulics engineering is not widespread and only limited studies are available. In this study, linearized St. Venant equations were used and the use of transfer matrix in ocean engineering was investigated for long waves in open channels, and numerical application was carried out. The results obtained through the transfer matrix method, which is quite easy to use, program and comprehend, showed similar results obtained from the characteristics method and finite differences method.  相似文献   

封闭系统中CaCO_3在天然水中溶解或沉淀的水化学后果     

钱会  李雨新 《地球科学与环境学报》1994,(2)

文章在计算水溶液化学组份平衡分布及其ｐＨ值的基础上，分析和讨论了封闭系统中ＣａＣＯ３溶解或沉淀所引起的水化学后果，并依据计算数据和借助作图的办法得出了如下结论，即ＣａＣＯ３溶解会使水溶液ｐＨ值增大，Ｈ２ＣＯ３含量减少；相反，ＣａＣＯ３沉淀会使水溶液ｐＨ值减小，Ｈ２ＣＯ３含量增多。  相似文献   

基于开源GIS的地震灾情速报信息收集与处置研究     

王斐斐  韩贞辉  樊华  宋鹏展 《震灾防御技术》2022,17(1):188-196

针对河南省灾情获取效率低的现实问题,设计基于QGIS的微信小程序,实现灾情速报员属性数据空间化,并自动分配拨打电话任务,灾情调查人员及时将通过拨打电话获取的灾情信息快速上报,实时动态展布,并快速统计灾情速报信息,生成地震有感范围图和地震灾情信息汇总报告,为地震抗震救灾指挥部决策提供支持,满足河南及邻区小震、弱震较多地区地震应急、应急演练工作需求,也为其他应急系统建设提供参考。  相似文献   

《北京西山地质志》中、英文本比较研究     

郑豪 《地质论评》2022,68(4):2022072013-2022072013

依据文本对勘的方法,从图片和文字两个方面对《北京西山地质志》中、英文本进行比较研究。图片方面,英文本作了大量的增补和解说,内容更为详实准确。文字方面,中、英文本目录存在明显差异。英文本序言和注释有其独到的价值和意义。中文本正文的细节增补,应是吸收了当时的最新研究成果。中、英文本比较研究为认识《北京西山地质志》的价值与地位提供了准确可靠的学术依据。  相似文献   

对等导航服务网格平台的设计与实现     

李绍俊  钟耳顺  张珣  王少华  李楷 《测绘科学》2015,40(5):148-153

针对网格环境下导航地图数据的共享与管理问题,文章提出以多级分区空间索引目录结构为基础的对等导航服务网格体系结构:分析了对等导航服务网格平台实现的关键技术,并基于Globus Toolkit设计实现了对等导航应用服务网格实验平台,提供了全国范围的地图浏览、定位监控、路径分析等服务。实验结果表明该平台能为位置服务应用提供高效的服务。  相似文献   

The influence of solar activity on the rainfall over India: Cycle-to-cycle variations     

K. M. Hiremath 《Journal of Astrophysics and Astronomy》2006,27(2-3):367-372

We use 130 years data for studying correlative effects due to solar cycle and activity phenomena on the occurrence of rainfall over India. For the period of different solar cycles, we compute the correlation coefficients and significance of correlation coefficients for the seasonal months of Jan–Feb (JF), Mar–May (MAM), June–Sept (JJAS) and Oct–Dec (OND) and,annual mean data. We find that: (i) with a moderate-to-high significance, Indian rainfall is correlated with the sunspot activity and, (ii) there is an overall trend that during the period of low sunspot activity, occurrence of rainfall is high compared to the period of high sunspot activity. We speculate in this study a possible physical connection between the occurrence of the rainfall and the sunspot activities and, the flux of galactic cosmic rays. Some of the negative correlations between the occurrences of the sunspot and rainfall activities obtained for different solar cycle periods are interpreted as effects of aerosols on the rain forming clouds due to either intermittent volcanic eruptions or due to intrusion of interstellar dust particles in the Earth’s atmosphere.  相似文献   

NGC 1624 (OCl 403, Cr 53) – A very young open cluster     

S. Sujatha  G. S. D. Babu 《Astrophysics and Space Science》2006,305(4):399-410

We present the first CCD photometric UBVRI observations of the not-so-well-studied open cluster NGC 1624 (OCl 403, Cr 53; α₂₀₀₀ = 04 h 40 m 36 s; δ₂₀₀₀ = + 50^˚ 27^′ 42″ Trumpler class = I 2 p N). This cluster was observed on 01 February 2004 with the 2 m Himalayan Chandra Telescope at Hanle using a LN2 cooled 2k × 2k CCD. The cluster presents differential reddening with E(B-V) values ranging from 0.70 to 0.90 mag, which could be attributed to the presence of the HII region wherein the cluster is embedded. It is found to be at a distance of 6.025 ± 0.5 kpc and the age of this cluster is estimated to be ∼3.98 × 10⁶ years. In view of these parameters, it can be considered as a young enough cluster located in the direction of the Perseus constellation with the galactic coordinates of l = 155^˚.35 and b = + 02 ^˚.58. Thus it could also be used as a suitable candidate for tracing the Outer Perseus spiral arm of our Galaxy. The initial mass function slope is derived as 1.65 ± 0.25 by applying the corrections for field star contamination and data incompleteness. This is in good agreement with the Salpeter value within the limits of errors.  相似文献