BP神经网络的训练样本集容量

本文试图解释用ＢＰ神经网络解界面反问题时效果不佳的原因。文中首先从信息量的角度提出了ＢＰ神经网络训练本集容量的概念，给出了它的定义及组织训练样本集时应遵循的原则和方法。对于如何用ＢＰ神经网络解界面反问题，给出了其基本步骤，并根据上述训练样本集容量的概念及界面反总理的特殊性，给出了组织界面反问题训练样本集的方法。     

Approaches for modeling longitudinal dispersion in pore-networks

The purpose of this study is to quantify the dispersivity in the longitudinal direction by upscaling pore scale mixing over a network domain and to verify the dispersivity with that obtained through the more rigorous upscaling technique, the Brownian particle tracking model (BPTM). We model a porous medium with a network of pore-units that are comprised of pore bodies and bonds of finite volume. Such a pore-unit is assumed to be a mixing cell with the steady state flow condition for a single fluid. Dispersivity can be obtained by solving the mixing cell model (MCM) for the concentration in each pore-unit and by averaging the concentrations for a large number of pore units (as a function of time and space). A minimal size of network that ascertains an asymptotic value of dispersivity was determined and verified with large size pore networks. This numerically computed dispersivity is compared with the results from the BPTM for the same porous medium and flow conditions. We show that the dispersivity obtained from the MCM is equally reliable for the heterogeneous pore-networks and can be estimated as a function of pore size heterogeneity. For homogeneous networks with the MCM, the iteration time step plays an important role. On the other hand, for networks with the BPTM, the assumption of intra-bond velocity profile affects the results.     

红层（盆）与金矿化关系的探讨

红层（盆）内外存在着工业金矿化现象，与红层（盆）有关的金矿化包括：次火山岩型、卡林型、穆龙套型、不整合脉型、风化壳型、热泉型以及砂金等众多类型。它们的形成过程及分布与红层（盆）关系密切。本文总结了与红层（盆）有关金矿化的成矿模式及找矿方向。     

Inversion of near-field waveform data for earthquake source rupture process (Ⅱ): Inversion of Chi Chi earthquake source, 20 September, 1999, Taiwan

The Chi Chi earthquake (Mw7.6) occurred at 17:47 UTC on Sept. 20,1999 (01:47 September 21, 1999, local time) in central Taiwan. CWB located the epi- center at (120.82°E; 23.85°N) and the focal depth 8 km. Chi Chi earthquake is the best documented earth- quake ever recorded. The abundance and quality of its near-source observations present an unparalleled op- portunity for studying the rupture history from a close distance. More than 400 free field digital accelerome- ters with 3-compon…     

Raman spectral analysis and genetic mechanism of pseudotachylyte in Xiaoqinling detachment fault

Veins and clasts of pseudotachylyte developed in the microbreccias of the detachment fault along the boundary of the Xiaoqinling metamorphic core complex. The Raman spectral analysis shows that there are three kinds of textures in the matrices of the pseudotachylyte, i.e. ultracataclastic fine-grained texture, cryptocrystalline texture and both of them with minute quantity of glass. The three different textures are the results of different degrees of ultracataclasis. This demonstrates that ultracataclasis-comminution-melting is the genetic mechanism of the pseudotachylytes in the Xiaoqinling detachment fault and the ultracataclasis-comminution dominates in their formation. Project supported by the National Natural Science Foundation of China (Grant No. 49472142).     

黄河流域分布式水文模型初步研究与进展

结合国家重点基础研究规划项目"黄河流域水资源演化规律与可再生性维持机理"的研究,综述了黄河流域分布式水文模型研究的主要进展,包括分布式水文模型的特点和基本结构、分布式水文模型中的数字高程模型(DEM)和水文学基础、地理信息系统(GIS)和遥感(RS)在分布式水文模拟中的应用等方面的内容,对未来分布式水文模型的研究提出几点认识。     

A layered model of the upper crust in the Aigion region of Greece,inferred from arrival times of the 2001 earthquake sequence

The western part of the Gulf of Corinth attracts attention due to its seismically active fault system and considerable seismic hazard. Detailed studies of the seismic activity of the region have been carried out especially as part of the so-called Corinth Rift Laboratory (CRL) Project. For standard earthquake locations, the CRL uses the HYPO algorithm and a special structural model that is composed of homogeneous layers (Rigo et al., 1996). This model was derived from a passive seismic experiment in a broader area around the western part of the Gulf. A significant part of the seismic activity is concentrated close to the town of Aigion, which was damaged by a strong earthquake in 1995. A sequence of smaller earthquakes occurred to the south of this town in the year 2001. In the present paper, we have used this sequence to derive an improved structural model for the region in the vicinity of the town of Aigion. This new model is based on the minimization of travel-time residuals. In particular, we used arrival times from a subset of 88 events recorded by at least 5 stations of the southern part of the CRL network, had magnitudes of over 2.3, and were recorded at the nearest station (station code AIO). A variant of the method of conjugate gradients has been used for this purpose. In comparison with the model derived by Rigo et al. (1996), the new model is characterized by a higher ν_P/ν_S velocity ratio and by higher velocities to a depth of about 7 km. The new model was derived with the aim to get more accurate locations of future events in the vicinity of the town of Aigion.