浙江670地区断裂构造频率与铀矿化的关系

本文利用数理统计的方法对670地区断裂构造进行地质统计。发现富铀矿的产出，不仅与断裂构造的性质、规模、形态、发育程度、组合形式、复合特征及力学性质有关，而且与断裂构造的频率有密切关系。即某一频率出规范围有利于铀矿（床）化点的产出。为指导该地区近矿找矿提供信息。     

The star formation histories of galaxies in the Sloan Digital Sky Survey

We present the results of a moped analysis of  ∼3 × 10⁵  galaxy spectra from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3), with a number of improvements in data, modelling and analysis compared with our previous analysis of DR1. The improvements include: modelling the galaxies with theoretical models at a higher spectral resolution of 3 Å, better calibrated data, an extended list of excluded emission lines and a wider range of dust models. We present new estimates of the cosmic star formation rate (SFR), the evolution of stellar mass density and the stellar mass function from the fossil record. In contrast to our earlier work the results show no conclusive peak in the SFR out to a redshift around 2 but continue to show conclusive evidence for 'downsizing' in the SDSS fossil record. The star formation history is now in good agreement with more traditional instantaneous measures. The galaxy stellar mass function is determined over five decades of mass, and an updated estimate of the current stellar mass density is presented. We also investigate the systematic effects of changes in the stellar population modelling, the spectral resolution, dust modelling, sky lines, spectral resolution and the change of data set. We find that the main changes in the results are due to the improvements in the calibration of the SDSS data, changes in the initial mass function and the theoretical models used.