Numerical instabilities of a local transmitting boundary

A local transmitting boundary is presented in a compact form, which can be directly incorporated into finite elements. The accuracy of the boundary is studied thoroughly for a one-dimensional model in order to clarify numerical instabilities introduced by the boundary. Discretization of the model and reflection from the boundary are rigorously considered in the study, and the mechanism of the instability is then illuminated in the frequency domain by the amplification of reflection from the boundary and the multi-reflection of wave motion in a finite computational region. Typical characteristics of the instability in the time domain are illustrated by numerical results of the simple model and explained completely by the mechanism. On the basis of this understanding of the mechanism, a modified transmitting boundary is devised and its stability criterion is given for the one-dimensional model.     

金川—过铝多阶段花岗岩体演化特征及其与成矿关系

可尔因岩体自前锋石英闪长岩-二长花岗岩-钾长花岗岩-二云母花岗岩-花岗伟晶岩,分布于同一复式背斜内,并具有时空的、多阶段的、连续系列演化特点。在岩石化学等方面是过铝、高碱质、富挥发组分F和稀有元素Li,Be等,并向晚阶段岩石富集。含矿岩体位于“岩浆树”顶端-二云母花岗岩-花岗伟晶岩带。伟晶岩围绕主岩体成群、带状分布。岩体成生于印支末期(206Ma)。     

贺兰山东麓冲沟裂点溯源迁移速率及其形成年龄的讨论

本文通过对洪积扇断层崖上升盘冲沟裂点位置的实测和研究,讨论了贺兰山东麓地区影响裂点溯源迁移速率的主要因素,建立了这一地区裂点位置与形成年龄关系的公式。据此确定贺兰山东麓断层全新世以来至少发生过三次类似1739年平罗大地震的古地震事件,强震的重复间隔时间大约在2500年至3500年     

烟熏记录地震仪的技术改造：ARA放大器的应用之二

对六十年代生产的烟熏记录地震仪进行技术改造:保留烟熏记录,保留65摆(或DD—1摆)以ARA积分放大器代替线性放大器,以线性笔头代替积分记录笔,增配电子报警器及交直流自动切换电源,组成新的地震观测仪器系统。技术改造方案在广东地震台网实施、两年来仪器运行正常、效果很好。     

A regional spectral nested multilevel primitive equation model

By means of vertical normal modes a regional nested multilevel primitive equation model can be reduced to sev-eral sets of shallow water equations characterized by various equivalent depths. Therefore, time integration of the model in spectral form can be performed in the manner similar to those used in the spectral nested shallow water equation model case.     

论永平铜矿区“层状矽卡岩”成因及与矿化的关系

永平铜矿产于中石炭统地层中,是一大型的海底火山热液沉积经后期构造、岩浆改造的块状硫化物矿床。矿区产出“层状矽卡岩”,其规模远大于岩浆侵入体,与围岩整合产出。本文的研究表明:“层状矽卡岩”并非侵入体与碳酸岩发生接触交代作用的产物,而是沉积—火山沉积经后期改造形成的。“层状矽卡岩”与矿体在空间上共存,时间上经历了相同的发展阶段,“层状矽卡岩”对矿化起了进一步富集的作用。     

Comparison of the rise of water level in the typical catchments,Three Gorges Reservoir area

Water level is an important index for studying hydrologic processes. Water level rise processes were studied in three catchments (catchment I, II, III in Chen Jiagou watershed in the Three Gorge Reservoir Area) with different areas to provide useful information to inform data extension from a gauged-catchment to an ungauged catchment. The results showed that there are seasonal changes in the dominant driving mode of the rise of the water level. The rise of the water level in March is likely mainly driven by the mode of stored-full runoff, and in September or October, it is mainly driven by Horton-flow. The correlation coefficients of all indexes were significant among the three catchments, suggesting that these catchments have similarities and that water level data extension is likely to be completed successfully between the large catchment (III-Catchment) and the small catchment (I-Catchment). It was confirmed that there is good similarity between the 0.6 km2 and 6 km2 catchments, and the data correlation is good between the catchments with the area differences in the Three Gorges Reservoir Area. In addition, the rise processes of the water level in the catchments were not only different under the same rain conditions, but this difference could also change with the rain condition.     

人类活动对鄱阳湖泥沙收支平衡的影响

以鄱阳湖流域内的赣江、抚河、信江、饶河和修水（五河）和鄱阳湖为研究对象,利用水文控制站的水文资料,分析了各流域内主要河流的入湖泥沙和鄱阳湖出湖泥沙特征,对鄱阳湖泥沙收支平衡进行了分析。结果表明：① 1955~2010年五河总入湖泥沙811.69 Mt,其中赣江（占59.7%）>信江（占13.7%）>修河（占10.2%）>抚河（占9.7%）>饶河（占6.7%）;② 径流量是影响入湖输沙量的最主要因素,入湖泥沙与入湖径流的季节特征一致;③ 水库的蓄水拦沙作用是五河入湖泥沙下降的主要原因,但水库对入湖泥沙的影响强度与水库库容和集水区的植被覆盖状况有关;植被覆盖变化对赣江、抚河、饶河和修河的入湖输沙量的影响明显;④ 1955~2010年,鄱阳湖总出湖泥沙560.10 Mt,其中1955~2000年出湖泥沙量呈降低趋势,但受鄱阳湖采砂影响,2001年以来出湖泥沙显著增加;丰水季长江水对鄱阳湖的顶托和倒灌,使出湖泥沙与出湖径流在时间上不同步;三峡工程的运行改变了（长）江（鄱阳）湖之间的水动力关系,长江倒灌泥沙显著减少;⑤ 受鄱阳湖采砂的影响,鄱阳湖泥沙平衡系统由净沉积转变为净侵蚀,1955~2000年入湖泥沙大于出湖泥沙,年均泥沙沉积约为1.41 mm;2001~2010年出湖泥沙大于入湖泥沙,加上采砂输出沙量,2001~2010年鄱阳湖泥沙净减少2 213.65 Mt。