Chemical enrichment in the early galaxy

New, precise abundance data for a large number of elements in a growing sample of extremely metal-poor stars are accumulating from the new 8-m telescopes. Combined with theoretical models, these results advance our understanding of the first generations of stars, whose nucleosynthesis products are fossilised in the oldest stars we see today and thus give clues to the earliest phases of evolution in the Galaxy. In particular, the heaviest elements give us insight into the different neutron capture mechanisms and the stellar sites where such elements could be produced. They also afford an independent way to determine the age of the Galaxy, by radioactive chronology. This revised version was published online in August 2006 with corrections to the Cover Date.     

On some observations of the thermal emission of iron flakes produced in a grinding wheel

A report is given of some laboratory experiments on the thermal emission of glowing iron flakes. Clear effects of polarization are found sometimes in flakes of small size, indicating polarization of a kind similar to that appearing in the thermal emission from narrow metallic filaments. Sudden flashes of light appear in the thermal emission from flakes produced in a grinding wheel. At the same time the flake splits into two parts. It is suggested that the flash is due to tribo-thermoluminescence. It seems possible that the infrared radiation of the solar corona may contain a faintly polarized component due to thermal emission from dust particles.Paper dedicated to Professor Hannes. Alfvén on the occasion of his 70th birthday, 30 May, 1978.     

78-Day periodicity in the solar 1–8 Å X-ray index during the ascending branch of cycle 21

In the present paper, the time series of 1–8 Å X-ray index for the time interval between January 1977 to September 1981 has been analyzed by carrying out power spectrum using Discrete Fourier Transform. The 78-day periodicity which is one-half of the period found from various solar parameters of cycles 20 and 21 by various authors, was found. This periodicity is thought to be related to the 152-day periodicity.     

Isotopes of rubidium in the Sun

Photoelectric measurements of photospheric velocity fields have been carried out with the Sacramento Peak Doppler Zeeman Analyzer. Emphasis was given to long periods and low spatial wavenumbers in deep photospheric layers, where the 5-min oscillations are less dominant.Multiple or double peaks cannot be detected in power spectra of the 5-min oscillations, provided that a sufficient number of physically independent points on the solar surface are observed.The most frequent wave-numbers in the spectra of 5-min oscillations (as well as of the low frequency field) agree with those derived from a model assuming statistically independent oscillators of 10 to 20 diameter. These two velocity fields are anti-correlated spatially.Kinetic power in the 20-to-50-min range of periods is closely linked to brightness changes in the same layer, an increase of brightness lagging about 250 sec behind rising motion. Granules can be excluded as a possible source for the appearance of low frequency flow patterns. Different explanations are suggested.On leave from Fraunhofer Institut, Freiburg, Germany.     

盾构机轴线方位角解算原理研究

以德国VMT公司的TMB制导系统SLS-T为例,主要解析了盾构机轴线方位角测量原理,并完整地推导了盾构机姿态参数公式。由于国外导向系统的核心原理不公开,因此本文的研究成果,为隧道施工工程技术人员深入理解激光导向系统原理以及开发国产的自动导向系统提供了理论基础。     

基于FME的DWG数据到ArcGIS转换的应用研究

本文针对工程实践中DWG数据到ArcGIS转换的实际需要,基于转换工具FME,采用FME Workbench构建转换模块对DWG数据转换的方法,研究了利用FME Workbench构建转换模块的关键技术和对转换后GIS数据的检查。通过以阜新腰梅力板的DWG数据为例,实现了对DWG数据到ArcGIS的Geodatabase数据的转换,并对转换后的数据进行检查、整理。结果证明,本文所采用的转换方法良好,节省了工作时间、提高了工作效率。     

长春市地名地址数据采集方案设计与实践

以长春市3.8 km~2实验区为例,介绍了地名地址数据采集的工艺流程、采集要求及实际采集遇到的问题为全面展开市区地名地址数据采集和数据库建立积累了经验,并提供技术支持。     

Splash detachment of sand particles under varying contact stress field of wind-driven raindrop impact

The effects of wind-driven rain (WDR) on sand detachment were studied under various raindrop obliquities. Results suggested a significant reduction in compressive stress on sand surfaces for a two-dimensional experimental set-up in a wind tunnel. During experiments, sand particles in splash cups were exposed to both wind-free rain (WFR) and WDR driven by horizontal winds of 6.4, 8.9 and 12.8 m s⁻¹ and rainfall intensities of 50, 60, 75 and 90-mm h⁻¹ to assess the sand detachment rate (D, in g m⁻² s⁻¹). The effects of sand moisture state (dry and wet) on the detachment of different-sized particles (0.20–0.50 and 0.50–2.00 mm, respectively) were also tested. Factorial analysis of variance showed that shear and compressive stress components evaluated by horizontal and vertical kinetic energy flux terms (KE_x and KE_y, respectively, in J m⁻² s⁻¹) along with their vector sum (KE_r, in J m⁻² s⁻¹) explained the variation in D. Neither sand size nor sand moisture was statistically significant alone although binary interactions of KE_r, KE_x and KE_y with the sand size and three-way interaction of KE_x, sand size and moisture were statistically significant. These results can be explained by size-dependent variation in sand compressibility and surface friction related to the total stress field developed by a given partition of shear and compressive stresses of wind-driven oblique raindrops (KE_x/KE_y). Further analysis of the variation of the unit sand detachment rate (D_u = D/KE_r = g J⁻¹) with rain inclination (α, in degrees) better revealed the effect of WDR obliquity on D_u that further changed with sand size class and moisture state. Finally, the difference in the resulting stress field differentiable by the oblique raindrop trajectories of the experiment over sand surface significantly affected the non-cohesive particle detachment rates, to some extent interacted with size-dependent compressibility and interface shear strength of sand grains.