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

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.     

Paleoenvironmental reconstruction of quaternary sedimentation in eastern Sri Lanka: An ichnological study

Quaternary sediment deposits are well exposed along the eastern coastal margin of Sri Lanka. Systematic trace fossil studies along with sediment characteristics have been carried out for the first time to interpret the paleoenvironment that prevailed during Quaternary sedimentation in eastern Sri Lanka. The trace fossils Thalassinoides, Skolithos and Polykladichnus have been recognized about 5m above the present mean sea level. Features of the major trace fossil, Thalassinoides, indicate that it was formed by Thalassinidean shrimp Calianassa. Isolated, vertical to steeply inclined, cylindrical to sub cylindrical tubes with thin internal wall lining and inner wall striations of Skolithos and Polykladichnus show that they were formed by polychaetes. The typical characteristic of Polykladichnus isY-shaped branching with slight enlargement at junctions. Morphology and association of burrows as well as mineralogy, grain size and roundness of sediments indicate that the environment prevailed was marine soft grounds of the intertidal zone. Presence of preserved fine-scale features of burrows indicate that the bioturbated sandy tidal flat was suddenly exposed to the tropical environment due to sea level regression in Quaternary periods. Due to the microbial activities of wall linings, burrows were preserved and it was supported by other microbial activities that produced secondary iron bearing minerals that suffered subsequent oxidation. The bio-origination of red sediments of eastern coastal area of the present study can be used to interpret the debatable origin of the red beds found in northwestern and southeastern coastal areas of the island.     

Present environment of Dam Lake Sambe,southwestern Japan: a geochemical study of bottom sediments

Geochemical analyses of lakebed and core sediments from Lake Sambe on the outskirts of Oda City in Shimane prefecture in southwestern Japan were carried out in order to assess the water quality and the concentration and distribution patterns of sixteen elements. The lake water showed a stratified condition with respect to dissolved O₂, and As, Fe, and Mn concentrations in the bottom layers which increased in the summer. The chemical composition of the sediments, as measured by X-ray fluorescence, included major and trace elements (P, Ca, Sc, Ti, V, Cr, Fe, Ni, Cu, Zn, As, Sr, Zr, Pb, and Th), and total sulfur (TS). Elevated values of As, Zn, V, Fe, P, and TS were present in several layers of the upper cores (from 0 to 5 cm) and other surface sediments. Increases in the abundances of these metals in lake sediments are probably related to the reducing condition of the sediments, fine-grained organic rich sediments, and post-depositional diagenetic remobilization. Moreover, correlations between the concentrations of trace metals and iron in the sediments suggest their adsorption onto Fe (oxy)hydroxides, whereas correlations with sulfur indicate that they were precipitated as Fe-sulfides. The average abundances of As, Pb, Zn, and Cu exceeded the lowest effect level and Interim Sediment Quality Guideline values that the New York State Department of Environmental Conservation and the Canadian Council of Ministers of the Environment determined to have moderate impact on aquatic organisms. In addition, concentrations of As and Zn exceeded the Coastal Ocean Sediment Database threshold value, indicating potentially toxic levels. Therefore, the presence of trace metals in the lake sediments may result in adverse effects on biota health.     

Understandings of Relationships between Agriculture and Biodiversity in Kunisaki GIAHS

<正>1 Characteristics of Kunisaki GIAS and aims of this research Kunisaki GIAHS in the Kunisaki peninsula and Usa area,Oita,Japan,is a system where forestry,agricultural production,and fisheries are sustained by the strong connection between Sawtooth Oak forest,multiple interlinked irriga tion ponds,and Seto Inland Sea(Vafadari 2013a;2013b;Hayashi 2013).This area receive around 1,500 mm of annual precipitation with a     

Inland penetration of the sea breeze over the suburban area of Tokyo

Observational results of the structure of the sea breeze over the urban and suburban areas of Tokyo for four summer days are presented.On two of these days, the inland penetration of the sea breeze front could be clearly traced. In one case, the sea breeze was first observed along the shores of Tokyo Bay around 0900 JST, and propagated in three hours through the Tokyo City area, the width of which is about 20 km. It then advanced inland at a rate of 16 km h^–1. Prior to the arrival of the sea breeze at the suburban site, the mixing height had remained at about 600 m for four hours. With the arrival of the sea breeze front, accompanied by an abrupt change in wind speed and direction, the mixing height increased sharply to 1700 m. It is suggested that this behavior and the structure of the front are intensified due to the urban effect, or the difference in the thermal characteristics between the urban and rural areas.On the days without a sea breeze front, the land breeze system during the early morning was less intense, allowing the sea breeze to develop simultaneously with the inland valley wind and easily form a large-scale local wind system during the morning hours. In both cases, the vertical motion accompanying the local wind system works as a feedback mechanism to control the local winds by modifying the thermal and pressure fields.     

Distribution of arsenic and other trace elements in the Holocene sediments of the Meghna River Delta, Bangladesh

Geochemical study of the Holocene sediments of the Meghna River Delta, Chandpur, Bangladesh was conducted to investigate the distribution of arsenic and related trace and major elements. The work carried out includes analyses of core sediments and provenance study by rare earth element (REE) analysis. Results showed that the cores pass downward from silty clays and clays into fine to medium sands. The uppermost 3 m of the core sediments are oxidized [average oxidation reduction potential (ORP) + 230 mV], and the ORP values gradually become negative with depths (−45 to −170 mV), indicating anoxic conditions prevail in the Meghna sediments. The REE patterns of all lithotypes in the study areas are similar and are comparable to the average upper continental crust. Arsenic and other trace elements (Pb, Zn, Cu, Ni, and Cr) have greater concentrations in the silts and clays compared to those in the sands. Positive correlation between As and Fe was found in the sediments, indicating As may be adsorbed on Fe oxides in aquifer sediments.     

I–P<Subscript>2</Subscript>O<Subscript>5</Subscript> diagrams as an indicator of depositional environment in marine sediments: preliminary findings (Sri Lanka)

The concentrations of Br and I in marine sediments have been used to categorize the sedimentary environments of different coastal regions of the world with respect to organic matter contents. The present study uses the concentrations of Br, I and P₂O₅ of different marine settings as a new proxy to interpret the depositional environments. A total of 150 coastal lagoon sediment samples (suspended sediments, surface sediments and sediment cores) were analyzed for Br, I and P₂O₅ concentrations by X-ray fluorescence spectrometry. They were compared with the Br, I and P₂O₅ concentrations of the 2004 Indian Ocean tsunami sediments. Sediments from various sources are separately clustered in I–Br plot and a trivial negative correlation is found for the whole plot. A similar correlation pattern exists in the I–P₂O₅ diagram. This correlation is explained by the distribution of marine plants (higher and lower) in different sedimentary environments of the coastal profile. Therefore, the concentration of I and its relation to P₂O₅ can be used as a tool to identify sediment depositional environments in marine settings.     

Thermochronology for the Granitic Pluton Related to Lead-Zinc Mineralization in Tsushima, Japan

Abstract: K–Ar datings and oxygen isotope analyses revealed a cooling history of the Uchiyama granitic pluton, which is genetically related to the Pb-Zn deposits (Taishu mine) in the Tsushima Islands, Japan. The pluton intrudes into the Paleogene Taishu Group to form the biotite-hornfels zone, while the Taishu vein-type Pb–Zn deposits occur in fissures developed in the non-hornfels zone about 1 to 3 km westward from the contact. Amphibole and biotite K-Ar ages of the pluton have a wide range from 19 to 13 Ma. Oxygen isotopes of the biotite and coexisting quartz grains indicate that isotopic exchange reactions have occurred under subsolidus conditions, and that the K-Ar ages are affected by various cooling rates in the pluton. The mineralization age of the Taishu ore deposits is obtained for the first time to be 15.40.8 Ma by a K-Ar age of 2 M ₁–muscovite in a calcite–quartz–muscovite–chlorite veinlet of the Shintomi orebody. Whole rock K-Ar ages of biotite-hornfels near the pluton represent similar ages to the ore deposits. Using blocking temperature calculated from reported diffusivity for argon, the pluton was cooled from 560 to 350C in the period of 17 to 14 Ma. The vein formation took place after the time when temperature in wall rocks of the pluton had dropped below the brittle-plastic transition (about 400C). These results imply that the cooling of the pluton has caused injection of magmatic fluids into meteoric hydrothermal systems, and the Pb-Zn mineralization has occurred due to this mixing at the age of about 15 Ma.     

Micro- and nano-inclusions in a superdeep diamond from São Luiz,Brazil

We report cloudy micro- and nano-inclusions in a superdeep diamond from São-Luiz, Brazil which contains inclusions of ferropericlase (Mg, Fe)O and former bridgmanite (Mg, Fe)SiO₃ and ringwoodite (Mg, Fe)₂SiO₄. Field emission-SEM and TEM observations showed that the cloudy inclusions were composed of euhedral micro-inclusions with grain sizes ranging from tens nanometers to submicrometers. Infrared absorption spectra of the cloudy inclusions showed that water, carbonate, and silicates were not major components of these micro- and nano-inclusions and suggested that the main constituent of the inclusions was infrared-inactive. Some inclusions were suggested to contain material with lower atomic numbers than that of carbon. Mineral phase of nano- and micro-inclusions is unclear at present. Microbeam X-ray fluorescence analysis clarified that the micro-inclusions contained transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn) possibly as metallic or sulfide phases. The cloudy inclusions provide an important information on the growth environment of superdeep diamonds in the transition zone or the lower mantle.     

新疆北部富蕴县沙尔布拉克玻安岩的地球化学特征及构造意义

详细的地球化学研究表明，新疆北部富蕴县沙尔布拉克中泥盆统北塔山组的辉石安山岩具有中等的SiO2含量（52.13%-60.45%)；高MgO(3.91%-9.31%)和相容元素（包括Ni、Cr、Co等）含量，以及高Mg^#和Al2O3／TiO2比值；低TiO2含量（0.21%-0.35%)；同时具有U型稀土元素分布模式；并强烈亏损高场强元素。这些特征均与玻安岩的地球化学特征一致，应属于玻安岩，形成于前弧环境。沙尔布拉克玻安岩的存在表明，古亚洲洋在早－中泥盆世向南发生了洋壳俯冲作用。