Comparison between iterative solution of symmetric and non‐symmetric forms of Biot's FEM equations using the generalized Jacobi preconditioner     

Kim‐Chuan Toh  Kok‐Kwang Phoon 《国际地质力学数值与分析法杂志》2008,32(9):1131-1146

Finite element discretization of Biot's consolidation equations can produce a symmetric indefinite system (commonly used in geomechanics) or a non‐symmetric system. While this difference appears to be minor, however, it will require the selection of entirely different Krylov subspace solvers with potentially significant impact on solution efficiency. The former is solved using the symmetric quasi‐minimal residual whereas the latter is solved using the popular bi‐conjugate gradient stabilized. This paper presents an extensive comparison of the symmetric and non‐symmetric forms by varying the time step, size of the spatial domain, choice of physical units, and left versus left–right preconditioning. The generalized Jacobi (GJ) preconditioner is able to handle the non‐symmetric version of Biot's finite element method equation, although there are no practical incentives to do so. The convergence behaviour of GJ‐preconditioned systems and its relation to the spectral condition number or the complete spectrum are studied to clarify the concept of ill‐conditioning within the context of iteration solvers. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

基于MODIS影像的2016—2017年东海赤潮高发期水体时空分布及其气象控制因子分析          下载免费PDF全文

李晨映  冯驰  梅琨 《应用海洋学学报》2024,43(1):095-105

近年来，东海区域赤潮灾害频发，对沿海地区的经济发展和海洋生态环境造成了极大的破坏。本研究基于赤潮暴发年2016—2017年夏季MODIS影像数据，采用半经验多光谱识别算法对东海夏季赤潮暴发期的水体类型分布特征进行反演。结果表明，赤潮高发期东海水体类型从近岸向开阔海域呈现浑浊水体 赤潮水体 混合水体 干净水体的时空分布特征。其中，硅藻和甲藻赤潮水体在空间分布上具有相互演替变化的特征。此外，通过对浙江省近岸的大陈站、石浦站和嵊泗站3个站点的气象因子进行主成分分析发现，气温、风速和天空云量对赤潮的生消演替起着积极的促进作用。  相似文献   

Optimizing interferometer experiments for cosmic microwave background B-mode measurements     

Jaiseung Kim 《Monthly notices of the Royal Astronomical Society》2007,375(2):615-624

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Multisite campaign on the open cluster M67 – III. δ Scuti pulsations in the blue stragglers     

H. Bruntt  D. Stello  J. C. Suárez  T. Arentoft  T. R. Bedding  M. Y. Bouzid  Z. Csubry  T. H. Dall  Z. E. Dind  S. Frandsen  R. L. Gilliland  A. P. Jacob  H. R. Jensen  Y. B. Kang  S.-L. Kim  L. L. Kiss  H. Kjeldsen  J.-R. Koo  J.-A. Lee  C.-U. Lee  J. Nuspl  C. Sterken  R. Szabó 《Monthly notices of the Royal Astronomical Society》2007,378(4):1371-1384

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A general solution for tide‐induced groundwater fluctuation in an estuarine‐coastal confined and unconfined aquifer system          下载免费PDF全文

Hsi‐Ting Fang  Yih‐Chi Tan  Mo‐Hsiung Chuang  Kai‐Yuan Ke  Po‐Chia Chen 《水文研究》2018,32(14):2239-2253

This paper presents an analytical solution to tide‐induced head fluctuations in a two‐dimensional estuarine‐coastal aquifer system that consists of an unconfined aquifer and a heterogeneous confined aquifer extending under a tidal river with a semipermeable layer between them. This study considers the joint effects of tidal‐river leakage, inland leakage, dimensionless transmissivity between the tidal‐river and inland confined aquifer, and transmissivity anisotropic ratios. The analytical solution for this model is obtained via the separation of variables method. Three existing solutions related to head fluctuation in one‐ or two‐dimensional leaky confined aquifers are considered as special cases in the present solution. This study shows that there is a threshold of tidal‐river confined aquifer length. When the tidal‐river length is greater than the threshold length, the inland head fluctuations remain sensitive to the leakage effect but become insensitive to the tidal‐river width and dimensionless transmissivity. Considering leakage and transmissivity anisotropy, this study also demonstrates that at a location farther from the river–inland boundary, head fluctuations increase with increasing leakage and transmissivity anisotropy; the maximum head fluctuation occurs when leakage and transmissivity anisotropy are both at their maximum values. The combined action of the 3 effects of loading, tidal‐river aquifer leakage, and inland aquifer leakage differs significantly according to various aquifer parameters. The analytical solution in this paper can be applied to demonstrate the behaviours of the head fluctuations of an estuarine‐coastal aquifer system, and the head fluctuations can be clearly described when the tidal and hydrogeological parameters are derived from field measurement data or hypothetical cases.  相似文献   

LOCATIONAL CHARACTERISTICS OF FOREIGN EQUITY JOINT VENTURE INVESTMENT IN CHINA, 1979–1985     

Chi Kin Leung 《The Professional geographer》1990,42(4):403-421

An examination of the locational characteristics of intended foreign equity joint venture (EJV) investment in China during the period 1979 to 1985 indicates that foreign EJV investment was highly concentrated in the coastal region, in the more developed areas of the provinces, and in large cities. The locational characteristics, however, differed between economic sectors and between countries of origin of investment. Although foreign EJV investment became spatially more dispersed through time, the impacts on the development of inland regions and backward areas in China remained limited.  相似文献   

The Keylong Serai rock avalanche, NW Indian Himalaya: geomorphology and palaeoseismic implications     

W. A. Mitchell  M. J. McSaveney  A. Zondervan  K. Kim  S. A. Dunning  P. J. Taylor 《Landslides》2007,4(3):245-254

This paper describes the geomorphology of rock avalanche deposits that resulted from a major mountain slope failure at Keylong Serai on the north slope of the Indian High Himalaya, an area of high altitude desert. Cosmogenic ¹⁰Be exposure ages of the widespread deposits indicate their formation 7,510 ± 110 years BP. Proxy records for this region of the Himalaya imply a similar dry climatic regime to the present day at this time, suggesting that precipitation was an unlikely trigger for this rock avalanche. An alternative mechanism associated with rock-wall stress relaxation is also unlikely, given the earlier timing of deglaciation in this area. Given the enormous volume of debris generated by this event, the most likely trigger for this mountain collapse and resultant rock avalanche is high ground acceleration during a great earthquake (M > 8). It is proposed that rock avalanches can be used to extend the limited palaeoseismic record and improve information on the recurrence interval of great earthquakes within the Himalaya arc.  相似文献   

Landslide susceptibility analysis and its verification using likelihood ratio, logistic regression, and artificial neural network models: case study of Youngin, Korea   总被引：8，自引：0，他引：8  

Saro Lee  Joo-Hyung Ryu  Ii-Soo Kim 《Landslides》2007,4(4):327-338

The likelihood ratio, logistic regression, and artificial neural networks models are applied and verified for analysis of landslide susceptibility in Youngin, Korea, using the geographic information system. From a spatial database containing such data as landslide location, topography, soil, forest, geology, and land use, the 14 landslide-related factors were calculated or extracted. Using these factors, landslide susceptibility indexes were calculated by likelihood ratio, logistic regression, and artificial neural network models. Before the calculation, the study area was divided into two sides (west and east) of equal area, for verification of the models. Thus, the west side was used to assess the landslide susceptibility, and the east side was used to verify the derived susceptibility. The results of the landslide susceptibility analysis were verified using success and prediction rates. The verification results showed satisfactory agreement between the susceptibility map and the existing data on landslide locations.  相似文献   

Textural and chemical variation in plagioclase phenocrysts from the 1980 eruptions of Mount St. Helens,USA     

Kim Berlo  Jon Blundy  Simon Turner  Chris Hawkesworth 《Contributions to Mineralogy and Petrology》2007,154(3):291-308

This study presents major- and trace-element chemistry of plagioclase phenocrysts from the 1980 eruptions of Mount St. Helens volcano. Despite the considerable variation in textures and composition of plagioclase phenocrysts, distinct segments have been cross-correlated between crystals. The variation of Sr and Ba concentration in the melt, as calculated from the concentration in the phenocrysts using partition coefficients, suggests the cores and rims crystallised from compositionally different melts offset by the plagioclase crystallisation vector. In both of these melts Sr and Ba are correlated despite the abundance of plagioclase in the 1980 dacites. We propose that rapid crystallisation of plagioclase upon magma ascent caused a shift in melt composition towards lower Sr and higher Ba, as documented in the rims of the phenocrysts. Although the cores of the phenocrysts crystallised at relatively shallow depths, they preserve the Sr and Ba of the deep-seated melts as they ascended from a deeper region. Further magma ascent resulted in microlite nucleation, which is responsible for a similar shift to even lower Sr concentration as observed in the groundmass of post-18 May 1980 samples. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

南极中山锚地与普里兹湾顶地形地貌特征          下载免费PDF全文

冯守珍  迟万清  薛佐 《极地研究》2007,19(2):79-86

本文使用中山锚地选址测绘资料及考察记录,对中山锚地现代地形地貌特征进行了分析。基于中山站附近海湾海底地形复杂多变,水深变化大的特点,将研究区域主要分为水下岸坡、海底峡谷和台地3个大的地貌单元,且对海底冲刷沟槽、水下低丘、洼地等次一级地貌类型发育进行了分析。同时指出位居台地上的中山锚地发育有裂隙带,此裂隙带横跨台地,长约3.8km,宽约80m,可能会在特定条件下,如地震、冰崩等,形成因海底斜坡失稳而向深海滑塌的地质灾害。  相似文献