Dynamic Characteristics of Marine Risers Conveying Fluid

The lateral vibration differential equation for a marine riser conveying fluid is derived by useof the small deflection theory.and the effect of internal flow velocity and top tension on the natural fre-quency of the riser is studied by use of FEM.At the same time,the preliminary relationship between thenatural frequency and riser span under different internal flow velocities is obtained,the effect of riser sup-ports on the vibration frequency is computed.It is found that the natural frequency of the marine riser in-creases with the increase of top tension.however decreases with the increase of internal flow velocity.In ad-dition,the frequency decreases drastically with the increase of riser span.     

新疆北山裂谷带铁染蚀变特征及其找矿意义

新疆北山裂谷带气候恶劣、地形复杂,为改善人工找矿效率低下的情况,研究利用遥感技术构建了控矿地质条件和蚀变异常信息的找矿模型.首先使用主成分分析法和波段比值法提取经过处理的新疆北山裂谷带遥感影像内的铁染蚀变异常信息.综合遥感信息和铁染蚀变特征,筛选出铁染蚀变异常套合较优的区域,圈定找矿有利区.最终圈定了3个白洼地有利找矿...