A study on the distribution of total bacteria,bacterial aggregates and heterotrophic bacteria in the sea     

H. Seki  I. Koike  E. Matsumoto  A. Hattori 《Journal of Oceanography》1972,28(3):103-108

The concentrations of total bacteria, bacterial aggregates and so-called heterotrophic bacteria were compared and discussed with special reference to the watermasses that vertically layered at the western North Pacific central region and the subarctic Pacific region.The concentrations of bacterial aggregates, having cells more than 25, were considerably uniform throughout the ocean depths. This was also shown indirectly by the measurements of size spectrum and organic constituents of particles, especially in the subsurface and deep watermasses. The so-called heterotrophic bacteria decreased in their concentration in deeper watermass, and the decrease was not obvious within each watermass but obvious among watermasses.  相似文献   

Extinction coefficients of amorphous carbon grains from 2100 Å to 340 μm     

C. Koike  H. Hasegawa  A. Manabe 《Astrophysics and Space Science》1980,67(2):495-502

Extinction measurements were made for three kinds of amorphous carbon grains in the range 2100 -340 m. Absolute values of extinction coefficients from different sources vary by almost constant factors. Wavelength dependences of extinction curves show a ^–1 or less steep fall off, against a ^–2 or steeper fall off of graphite grains. Small humps are found around 6.3, 8, 13.3 and 90 m, although their origins are not yet clear. The infrared properties of amorphous carbon grains suggest that they could supply a significant amount of far-infrared emission noted in recent astronomical observations.  相似文献   

Magnetotelluric resistivity modeling for 3D characterization of geothermal reservoirs in the Western side of Mt. Aso, SW Japan   总被引：1，自引：1，他引：1  

Hisafumi Asaue  Katsuaki Koike  Toru Yoshinaga  Shinichi Takakura   《Journal of Applied Geophysics》2006,58(4):296

Geothermal reservoirs are usually located at a depth range of 2 to 5 km, so to efficiently utilize such resources an advanced prospecting method is needed to detect these deep geologic structures. This study aimed to three-dimensionally characterize geothermal reservoirs by a combination of Magnetotelluric (MT) survey, inversion analysis of apparent resistivity, and interpolation of the resistivity data obtained. The western side of Mt. Aso crater, southwest Japan, was chosen as the case study area. Three hot springs exist there and a fault is assumed to go in the direction connecting them. A MT survey was carried out at 26 sites and the data processed by a remote reference method to reduce artificial noises. Based on skewness and Mohr circle analyses of the impedance tensor, the local geologic structure at each site could be approximated as horizontally layered and therefore, a one-dimensional inversion analysis was applied to the MT raw data. The resultant resistivity column data were then interpolated by the three-dimensional optimization principle method. The resistivity distributions obtained clarified continuous conductors with especially low resistivity (less than 10 Ω·m) at the hot springs along the fault. Because the resistivity decreases largely with an abundance of clay minerals, the conductors could be considered to correspond with the cap rocks. Thus, two geothermal reservoirs, whose shapes were estimated to be pillar, were detected under the cap rocks in an elevation range of − 1000 to − 3000 m. By comparing the resistivity distributions with the temperature distributions based on fluid-flow calculations at a steady state using FEM, the validity of the location and dimension of the estimated reservoirs were confirmed.  相似文献   

Three-dimensional distribution analysis of phosphorus content of limestone through a combination of geostatistics and artificial neural network   总被引：1，自引：0，他引：1  

Katsuaki Koike  Bin Gu  Michito Ohmi 《Natural Resources Research》1998,7(3):197-210

One of the factors that determines the suitability of limestone for industrial use and its commercial value is phosphorus (P) content, i.e., the weight percentage of phosphorus contained in small quantities of limestone. Because P content changes locally, geostatistical techniques including semivariogram, ordinary kriging, and conditional indicator sequential simulation were used in this study to identify the spatial correlation of P content and to estimate its three-dimensional distribution in an open-pit mine. The P content data at 43,000 points of five different bench levels were analyzed. It was found that the horizontal semivariograms produced by using the data at the same bench level show anisotropic behavior and are represented by the sum of two spherical models with different ranges and sills. The twelve vertical semivariograms were also constructed from P content in boring cores. After these semivariograms were classified into four types, a multilayered neural network was applied to clarify the horizontal distribution of each one. One of the twelve semivariograms was assigned to an arbitrary grid point in the study area by the criterion that its type is the same as the one estimated at the point and the borehole site producing the semivariogram is the nearest to the point. With this technique, ordinary kriging combined with the semivariogram of borehole data provided a proper estimation of P content in the depth direction.  相似文献   

Diurnal and inter-monthly variation of land surface heat fluxes over the central Tibetan Plateau area   总被引：4，自引：1，他引：3  

Y. Ma  S. Fan  H. Ishikawa  O. Tsukamoto  T. Yao  T. Koike  H. Zuo  Z. Hu  Z. Su 《Theoretical and Applied Climatology》2005,80(2-4):259-273

Summary The energy and water cycle over the Tibetan Plateau play an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. Using field observational data observed from the GAME/Tibet (GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Tibetan Plateau) and the CAMP/Tibet (CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau), some results on the local surface energy partitioning (diurnal variation, inter-monthly variation and vertical variation etc.) are presented in this study.The study on the regional surface energy partitioning is of paramount importance over heterogeneous landscape of the Tibetan Plateau and it is also one of the main scientific objectives of the GAME/Tibet and the CAMP/Tibet. Therefore, the regional distributions and their inter-monthly variations of surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) are also derived by combining NOAA-14/AVHRR data with field observations. The derived results were validated by using the ground truth, and it shows that the derived regional distributions and their inter-monthly variations of land surface heat fluxes are reasonable by using the method proposed in this study. Further improvement of the method and its applying field were also discussed.  相似文献   

Extending Multivariate Space-Time Geostatistics for Environmental Data Analysis   总被引：1，自引：0，他引：1  

Chunxue Liu  Katsuaki Koike 《Mathematical Geology》2007,39(3):289-305

Environmental studies require multivariate data such as chemical concentrations with space-time coordinates. There are two general conditions related to such data: the existence of correlations among the coregionalized variables and the differences in numbers of data which occur because of insufficient data caused by measurement error or bad weather conditions. This study proposes geostatistical techniques for space-time multivariate modeling that take into consideration these correlations and data absences. These techniques consist of suitable modeling of semivariograms and cross-semivariograms for quantifying correlation structures among multivariables and of extending standardized ordinary cokriging. The tensor product cubic smoothing surface method is used for space-time semivariogram modeling. These methods are applied to the chemical component data of the Ariake Sea, a typical closed sea in southwest Japan. In order to clarify environmental changes in the Ariake Sea, the concentration data of four nutritive salts (NO₂–N, NO₃–N, NH₄–N, and PO₄–P) at 38 stations over 25 years are used as environmental indicators. For each of the kinds of data, there are spaces and times for which there is no data available. The effectiveness of the modeling of space-time semivariograms and the high estimation capability of the extended cokriging are demonstrated by cross-validation. Compared with ordinary kriging for a single variable, multivariate space-time standardized ordinary cokriging can provide a more detailed concentration map of nutritive salts and while elucidating their temporal changes over sparsely spaced data areas. In the space-time models by ordinary kriging, on the other hand, smooth trends are obvious.  相似文献