The Spatial and Temporal Characteristics of Pc3 Geomagnetic Activity over Canada in 2000, as a Guide to Planning the Times of Aeromagnetic Surveys

Geomagnetic activity affects aeromagnetic surveys. Geomagnetic variations are quite complex and can be quantified in different ways. A measure of geomagnetic activity that is useful for planning aeromagnetic surveys is the Pc3 pulsation index developed by the Australian Space Weather Agency. Purposeful to developing guidelines for planning aeromagnetic surveys in Canada, we study the variations in Pc3 index amplitude over Canada in 2000. This study shows distinct patterns associated with the sub-auroral zone, the auroral zone, and the polar cap. Average Pc3 index activity is higher during the months of February, July, September, and November in the auroral and sub-auroral zones. The station in the polar cap exhibits maximum activity near midday during the summer months. Detailed analysis of a magnetic storm shows that Pc3 index amplitude during the beginning of the solar storm is least important at the polar cap. The mean Pc3 index also relates to solar wind parameters such as the solar wind velocity and the vertical polarity of the interplanetary magnetic field. Analysis of the morning maximum of the Pc3 index observed in the auroral zone can be used to develop guidelines for planning aeromagnetic surveys in Canada and other areas of the world affected by auroral zones.     

建筑抗震构件中屈曲约束支撑结构研究新进展

详细介绍了近年来中国学者在屈曲约束支撑研究方面取得的研究成果，着重讨论了屈曲约束支撑构件（核心单元、约束机构、无黏结构造层）和整体抗震性能以及设计方法的研究现状。结果表明：屈曲约束支撑以其良好的耗能性能具有很好的发展潜力，屈曲约束支撑的适用范围不断拓展，结构形式更趋多样化，设计方法不断优化。     

滇西北香格里拉市红牛—红山铜矿勘查系统模型

滇西北红牛—红山铜矿床是义敦—沙鲁里岛弧上与晚白垩纪中酸性侵入体有关的典型的斑岩-矽卡岩-热液型铜矿床。本文通过对其成矿地质背景、矿床地质特征、矿化富集规律及成矿模式、矿床地球物理和地球化学特征的综合研究，建立了红牛—红山铜矿床的"大比例尺地质填图和综合研究+重力+激电和高精度磁测+土壤化探测+工程验证"组合勘查技术方法、"燕山晚期石英二长斑岩+接触带矽卡岩和层间破碎带矽卡岩+重力低异常+高磁异常+高视极化率和低视电阻率异常+Cu-Mo-Pb-Zn-Ag-Au等元素综合异常"组合勘查模型。地质调查研究确定矿床成矿地质体和找矿地质体、矿化类型及其空间分布规律，建立矿床"四位一体"的成矿模式和区域-矿区地质找矿模型。区域中小比例尺的土壤化探测量确定区域找矿靶区，大比例尺土壤化探测量进一步缩小找矿靶区，逼近矿体赋存部位。矿区处于1∶5万土壤测量圈定的Cu-Pb-Zn-Mo-Au-Ag元素综合高异常区，1∶2.5万土壤测量圈出Cu-Pb-Zn-Ag-W元素综合异常面积较大、强度高、浓集中心明显、元素套合好，与矿区铜（铁）矿体赋存区域异常相对应。区域重力低异常区和正磁异常强度高区域是重要的找矿靶区，矿区大比例尺磁异常和激电异常区确定了矿体的空间位置和产状；矿区铜（铁）矿体赋存区为低视电阻率、高视极化率异常区，高精度磁测表现为正负磁异常相伴。矿区地质-地球化学-地球物理综合勘查模型对矿区深边部找矿起到重要的指导作用。     

DO WE NEED TO MODEL PLATES AT ALL?

The historical method of obtaining equatorial coordinates for stars observed via astronomical photography has been to convert the measured coordinates to equatorial coordinates with the aid of a plate model which corrects for a variety of effects. However, we now have at our disposal novel smoothing techniques, of considerable generality, which in conjunction with modern star catalogues can reproduce the essence of the plate model while dramatically minimizing both the fortuitous and systematic errors of observation. In this paper we demonstrate that, with this technique and extant catalogues, one can obtain, with at least the same precision and better accuracy, the information necessary to transform the measured coordinates successfully into standard coordinates by a process that involves no sophisticated model for the plate. Using external checks we estimate the increase in accuracy to be of the order of 25 per cent.     

A 408-MHz variability study of two fields in the region 6h30m, +45°

Variability in 408-MHz flux density, over a 1-yr interval between 1995 and 1996, has been investigated using the DRAO Synthesis Telescope for a complete sample of 322 sources with S _408 MHz > 80 mJy at galactic latitude b  = 15°; four sources are found to show significant flux density variations. These results, taken with those from a similar study at b  = 58°, indicate that 408-MHz variability over a time-scale of 1 yr is more uncommon than has previously been thought; variations at a level >10 per cent could have been detected in a statistically complete sample of about 150 of these sources and none was found. Variability over a period of 18 yr has also been investigated by comparing the DRAO data with those from the B3 catalogue for 182 sources with S _408 MHz > 200 mJy; five variables are found. Large flux density variations over a period of 18 yr are much more common than over 1 yr, with roughly one source in 15 showing variations at the 15 per cent level or greater. The statistics are not good enough to show any conclusive evidence for a dependence of variability on galactic latitude. Roughly half of the variable sources have spectra that are steep at high frequencies and flatten at low frequencies; the other half have flat radio spectra over the entire frequency range. Simultaneous observations at 1420 MHz, also with the DRAO Synthesis Telescope, have been used to investigate variability at this frequency as well, and indicate that over a period of 1 yr roughly half of the flat-spectrum sources vary at the 5 per cent level or greater.     

A ROSAT survey of Wolf–Rayet galaxies — II. The extended sample

We present results from an ongoing X-ray survey of Wolf–Rayet (WR) galaxies, a class of objects believed to be very young starbursts. This paper extends the first X-ray survey of WR galaxies by Stevens &38; Strickland by studying WR galaxies identified subsequent to the original WR galaxy catalogue of Conti.   Out of a sample of 40 new WR galaxies a total of 10 have been observed with the ROSAT PSPC, and of these seven have been detected (NGC 1365, NGC 1569, I Zw 18, NGC 3353, NGC 4449, NGC 5408 and a marginal detection of NGC 2366). Of these, all are dwarf starbursts except for NGC 1365, which is a barred spiral galaxy possibly with an active nucleus. We also report on observations of the related emission-line galaxy IRAS 0833+6517.   The X-ray properties of these galaxies are broadly in line with those found for the original sample; they are X-ray overluminous compared with their blue luminosity and have thermal spectra with typically kT  ∼ 0.4 − 1.0 keV. There are some oddities: NGC 5408 is very overluminous in X-rays, even compared with other WR galaxies; I Zw 18 has a harder X-ray spectrum; NGC 1365, although thought to contain an active nucleus, has X-ray properties that are broadly similar to other WR galaxies, and we suggest that the X-ray emission from NGC 1365 is due to starburst activity.   A good correlation between X-ray and blue luminosity is found for the WR galaxy sample as a whole. However, when just dwarf galaxies are considered there is little evidence of correlation. We discuss the implications of these results on our understanding of the X-ray emission from WR galaxies and suggest that the best explanation for the X-ray activity is starburst activity from a young starburst region.     

区域矿产资源经济研究的发展趋势及值得注意的若干问题

区域矿产资源经济研究的发展趋势是：区域矿产资源经济研究与人口、环境科学汇流,更加注重应用研究,研究目标的多元化,研究地域的扩大化,研究方法的现代化．值得重视的几个问题有：区域矿产资源可持续发展问题;区域矿产资源合理有效利用的客观标准;区域矿产资源的经济和人口承载能力;计算机技术的应用;人工神经网络等现代科学技术的应用;区域矿产资源资产评估的理论与方法;区域矿产资源经济研究模型系统的开发等．     

奉献农业 发展学科——对黄秉维院士农业研究工作的认识

简述了黄秉维院士的农业研究工作的光辉历程,分析了黄秉维农业研究工作的特色,强调学习黄秉维的精神.