Chaos in cosmic ray air showers     

Takashi Kitamura  Soji Ohara  Takeharu Konishi  Katsufumi Tsuji  Michiyuki Chikawa  Wasaburo Unno  Isao Masaki  Kenji Urata  Yukihiro Kato 《Astroparticle Physics》1997,6(3-4):279-291

Unexpected chaotic features are found in time series of arrival time intervals of successive air showers with (E > 3 × 10¹⁴ eV). Over 99 % of air shower arrival time intervals obey the Poisson distribution law representing stochastic behaviors, but occasionally there are air showers showing real chaotic behaviors as distinguished from both random and colored noises. With two systems of the Kinki university installations, we found 13 cases showing chaotic time series in 3.36 yr with the system-1 and the 1.37 yr with the system-2. Five out of 10 chaotic air showers of the Kinki installation are detected during the same time zone also by the Osaka City university installation which is at 115 km distance from the Kinki one. In a remarkable example of September 19, 1991, the correlation dimension was observed to have dropped from about 4 to the minimum of 1.3 and recovered smoothly in about 38 h. The chaos structure in this case is detected in nearly the same time zone at the Ohya station of the Institute for Cosmic Ray Research, University of Tokyo, which is separated from the Kinki one by 460 km. Formation of chaos structure due to energetic cosmic ray dust particles is suggested. Progress of cosmic ray physics may be expected with the study of air showers marked with chaos.  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   

Application of the Dugdale crack model to the stress-strain relations and bulk moduli of a granite     

Hitoshi Oda  Isao Suzuki  Kiyoshi Seya 《Tectonophysics》1984,110(3-4):297-315

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Light utilization efficiency of phytoplankton in the Western Subarctic Gyre of the North Pacific during summer     

Yuichi Nosaka  Tomonori Isada  Isao Kudo  Hiroaki Saito  Hiroshi Hattori  Atsushi Tsuda  Koji Suzuki 《Journal of Oceanography》2014,70(1):91-103

We investigated the water-column light utilization efficiency (Ψ) of phytoplankton photosynthesis in the Western Subarctic Gyre (WSG) of the North Pacific during summer 2008. The Ψ values (0.64–1.86 g C [g Chl a]^?1 [mol photon]^?1 m²) obtained were observed to increase significantly with decreasing daily photosynthetic available radiation (PAR) and were generally higher than those of previous studies, not only from the subarctic Pacific but also from the world’s oceans. To examine the effect of iron availability on Ψ in the WSG, Ψ values were estimated from the data of two in situ iron fertilization experiments: the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study I (SEEDS-I) and II (SEEDS-II). We found that iron availability did not affect Ψ values. Overall, this study revealed that Ψ values changed remarkably in the WSG during the summer, and that higher values were found at the stations where moderate PAR levels (ca. 10–30 mol photons m^?2 day^?1) were observed and where autotrophic flagellates predominated in the phytoplankton assemblages.  相似文献   

Environmental Factors Affecting the Occurrence and Production of the Spring Phytoplankton Bloom in Funka Bay, Japan     

Isao Kudo  Katsuhiko Matsunaga 《Journal of Oceanography》1999,55(4):505-513

The concentration of nutrients was measured during the spring phytoplankton bloom in Funka Bay over a 5-year period (1988–92). During the winter mixing period, nutrient concentrations were similar in every year except in 1990 when a high concentration of silicate was observed. There was interannual variation in the onset of the bloom, presumably depending on the stability of the water column. The bloom developed in early March when the Oyashio water (OW), which has a lower density than the existing winter water, flowed into the bay and the pycnocline formed near the bottom of the euphotic zone. In this case, high chl a was found only in the euphotic zone and nutrient utilization was limited to this zone. In the year when the inflow of OW was not observed by April, the bloom took place at the end of March without strong stratification and high chl a was found in the whole water column, accompanied by a decrease in nutrients. Interannual differences were found not only at the beginning of the decrease, but also in the thickness of the layer which showed a decrease in nutrients. Primary production from the beginning to the end of the spring bloom was estimated from the nutrient budget before and after the spring bloom. The integrated production over the spring bloom period ranged from 25 to 73 g C m^-2, which accounts for 19–56% of the annual production in this bay. We found that the timing of the bloom was strongly dependent on the inflow of OW, but the amount of production was not clearly related to this timing.  相似文献   

Vertical profiles of nitrous oxide and dissolved oxygen in marine sediments     

Toshihiro Usui  Isao Koike  Norio Ogura   《Marine Chemistry》1998,59(3-4)

The whole core squeezing method was used to simultaneously obtain profiles of nitrous oxide (N₂O), nitrogenous nutrients, and dissolved oxygen in sediments of Koaziro Bay, Japan (coastal water), the East China Sea (marginal sea), and the central Pacific Ocean (open ocean). In the spring of Koaziro Bay, subsurface peaks of interstitial N₂O (0.5–3.5 cm depth) were observed, at which concentrations were higher than in the overlying water. This was also true for nitrate (NO₃⁻) and nitrite (NO₂⁻) profiles, suggesting that the transport of oxic overlying water to the depth through faunal burrows induced in situ N₂O production depending on nitrification. In the summer of Koaziro Bay, sediment concentrations of N₂O, NO₃⁻ and NO₂⁻ were lower than in the overlying water. In most East China Sea sediments, both N₂O and NO₃⁻ decreased sharply in the top 0.5–2 cm oxic layer (oxygen: 15–130 μM), which may have indicated N₂O and NO₃⁻ consumption by denitrification at anoxic microsites. N₂O peaks at subsurface depth (0.5–6.5 cm) implied in situ production of N₂O and/or its supply from the overlying water through faunal burrows. However, the occurrence of the latter process was not confirmed by the profiles of other constituents. In the central Pacific Ocean, the accumulation of N₂O and NO₃⁻ in the sediments likely resulted from nitrification. Nitrous oxide fluxes from the sediments, calculated using its gradient at the sediment–water interface and the molecular diffusion coefficient, were −45 to 6.9 nmolN m⁻² h⁻¹ in Koaziro Bay in the spring, −29 to −21 nmolN m⁻² h⁻¹ in the summer, −46 to 37 nmolN m⁻² h⁻¹ in the East China Sea, 0.17 to 0.23 nmolN m⁻² h⁻¹ in the equatorial Pacific, and <±0.2 nmolN m⁻² h⁻¹ in the subtropical North Pacific, respectively.  相似文献