A dense seismic network was installed in the capital region of China in recent years,which makes it possible to resolve the focal mechanisms of small earthquakes. We gathered large earthquake focal mechanisms from the...A dense seismic network was installed in the capital region of China in recent years,which makes it possible to resolve the focal mechanisms of small earthquakes. We gathered large earthquake focal mechanisms from the last fifty years and moderate or small earthquake focal mechanisms from between 2002 and 2004,and calculated the present tectonic stress field of the capital region by the grid search method, which weighs different sized earthquakes and can improve the accuracy of the stress field inversion. The analysis of inversion results of different sub-regions shows that the azinuth of the maximum principal compressive stress axis is NE43°- 86° in the Beijing-Zhangjiakou-Datong area,NE38°-86° in the Tangshan area,and NE79°- 81° in the Xingtai area. Inversion results of this paper are similar to previous results,which proves the correctness of the approach. As revealed by the results,the stress field of the capital region is characterized by overall consistency and sub-regional differences. This study provides reference for earthquake mechanism explanation and geodynamics research.展开更多
When senors transmit their data to the sink via multi-hop communication, the sensors closer to the sink are burdened with heavy relay traffic and tend to die early. On the contrary, if all sensors transmit datas to th...When senors transmit their data to the sink via multi-hop communication, the sensors closer to the sink are burdened with heavy relay traffic and tend to die early. On the contrary, if all sensors transmit datas to the sink via single-hop communication, the sensors further from the sink will die much more quickly than those closer to the sink. In this paper, we first develop an analytical model to derive the optimal cluster radius. Then we propose a mixed communication method on grid-based where the sensors can transmit data to the sink in either single-hop or multi-hop. Finally, we conduct extensive experiments and show that our method outperforms LEACH and HEED in terms of network lifetime by balancing energy consumption.展开更多
The study on seepage flow passing through single fractures is essential and critical for understanding of the law of seepage flow passing through fracture networks and the coupling mechanisms of seepage field and stre...The study on seepage flow passing through single fractures is essential and critical for understanding of the law of seepage flow passing through fracture networks and the coupling mechanisms of seepage field and stress field in rock masses.By using the fractal interpolation to reconstruct a natural coarse fracture,as well as taking into account the microstructure of the fracture,the numerical simulation of seepage flow passing through the coarse fractures with two distinct vertical scaling factors is conducted based on the MRT-LBM model of the lattice Boltzmann method.Then,after obtaining the length of the preferential flow pathway,the permeability of the two kinds of fractures is estimated respectively.In view of difficulties in locating the preferential flow pathway of natural fracture networks,by numerical tests a transect permeability weighted algorithm for estimating the fracture network permeability is proposed.The algorithm is not specific to one or more particular preferential flow pathways,but considers the contribution of each section to hinder the fluid passing through the medium.In order to apply the new algorithm,by capturing the structure of fracture networks based on the image-processing technique,the numerical simulations of seepage flow passing through two groups of natural fracture networks is carried out,the permeability is forecasted and the partial flows are reproduced for both cases.It is found that the preferential flow pathway emerges at the beginning of evolution,then is strengthened subsequently,and finally reaches a steady status.Furthermore,by using the proposed method some details on local flow can be clearly observed such as backflows and vortices at local branches can exist simultaneously and so forth,suggesting the validness of the proposed method for multiscale simulations of seepage flow.展开更多
Surface remeshing is widely required in modeling, animation, simulation, and many other computer graphics applications. Improving the elements' quality is a challenging task in surface remeshing. Existing methods ...Surface remeshing is widely required in modeling, animation, simulation, and many other computer graphics applications. Improving the elements' quality is a challenging task in surface remeshing. Existing methods often fail to efficiently remove poor-quality elements especially in regions with sharp features. In this paper, we propose and use a robust segmentation method followed by remeshing the segmented mesh. Mesh segmentation is initiated using an existing Live-wire interaction approach and is further refined using local mesh operations. The refined segmented mesh is finally sent to the remeshing pipeline, in which each mesh segment is remeshed independently. An experimental study compares our mesh segmentation method as well as remeshing results with representative existing methods. We demonstrate that the proposed segmentation method is robust and suitable for remeshing.展开更多
基金sponsored by the Special Fund of Fundamental Scientific Research Operating Expenses for Higher School of Central Government(Projects for creation teams ZY20110101)the Special Fund for the Earthquake Scientific Research of China(201208009)National Natural Science Foundation of China(41074072)
文摘A dense seismic network was installed in the capital region of China in recent years,which makes it possible to resolve the focal mechanisms of small earthquakes. We gathered large earthquake focal mechanisms from the last fifty years and moderate or small earthquake focal mechanisms from between 2002 and 2004,and calculated the present tectonic stress field of the capital region by the grid search method, which weighs different sized earthquakes and can improve the accuracy of the stress field inversion. The analysis of inversion results of different sub-regions shows that the azinuth of the maximum principal compressive stress axis is NE43°- 86° in the Beijing-Zhangjiakou-Datong area,NE38°-86° in the Tangshan area,and NE79°- 81° in the Xingtai area. Inversion results of this paper are similar to previous results,which proves the correctness of the approach. As revealed by the results,the stress field of the capital region is characterized by overall consistency and sub-regional differences. This study provides reference for earthquake mechanism explanation and geodynamics research.
文摘When senors transmit their data to the sink via multi-hop communication, the sensors closer to the sink are burdened with heavy relay traffic and tend to die early. On the contrary, if all sensors transmit datas to the sink via single-hop communication, the sensors further from the sink will die much more quickly than those closer to the sink. In this paper, we first develop an analytical model to derive the optimal cluster radius. Then we propose a mixed communication method on grid-based where the sensors can transmit data to the sink in either single-hop or multi-hop. Finally, we conduct extensive experiments and show that our method outperforms LEACH and HEED in terms of network lifetime by balancing energy consumption.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2011CB013505)the National Natural Science Funds for Distinguished Young Scholar(Grant No.50925933)
文摘The study on seepage flow passing through single fractures is essential and critical for understanding of the law of seepage flow passing through fracture networks and the coupling mechanisms of seepage field and stress field in rock masses.By using the fractal interpolation to reconstruct a natural coarse fracture,as well as taking into account the microstructure of the fracture,the numerical simulation of seepage flow passing through the coarse fractures with two distinct vertical scaling factors is conducted based on the MRT-LBM model of the lattice Boltzmann method.Then,after obtaining the length of the preferential flow pathway,the permeability of the two kinds of fractures is estimated respectively.In view of difficulties in locating the preferential flow pathway of natural fracture networks,by numerical tests a transect permeability weighted algorithm for estimating the fracture network permeability is proposed.The algorithm is not specific to one or more particular preferential flow pathways,but considers the contribution of each section to hinder the fluid passing through the medium.In order to apply the new algorithm,by capturing the structure of fracture networks based on the image-processing technique,the numerical simulations of seepage flow passing through two groups of natural fracture networks is carried out,the permeability is forecasted and the partial flows are reproduced for both cases.It is found that the preferential flow pathway emerges at the beginning of evolution,then is strengthened subsequently,and finally reaches a steady status.Furthermore,by using the proposed method some details on local flow can be clearly observed such as backflows and vortices at local branches can exist simultaneously and so forth,suggesting the validness of the proposed method for multiscale simulations of seepage flow.
基金the National Natural Science Foundation of China(Nos.61772523,61372168,61620106003,and 61331018)supported by a Chinese Government Scholarship
文摘Surface remeshing is widely required in modeling, animation, simulation, and many other computer graphics applications. Improving the elements' quality is a challenging task in surface remeshing. Existing methods often fail to efficiently remove poor-quality elements especially in regions with sharp features. In this paper, we propose and use a robust segmentation method followed by remeshing the segmented mesh. Mesh segmentation is initiated using an existing Live-wire interaction approach and is further refined using local mesh operations. The refined segmented mesh is finally sent to the remeshing pipeline, in which each mesh segment is remeshed independently. An experimental study compares our mesh segmentation method as well as remeshing results with representative existing methods. We demonstrate that the proposed segmentation method is robust and suitable for remeshing.