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Sapporo, Japan

Katagiri K.,Hokkaido University | Yabe K.,Sapporo City University | Nakamura F.,Hokkaido University | Sakurai Y.,Docon Co.

To identify the causes of the rapid expansion of the semi-emergent Phalaris arundinacea L. community in a nutrient-loaded river, we investigated the factors that determine the distribution of the Phalaris and other aquatic macrophyte communities and the shoot growth of P. arundinacea. The Phalaris community was distributed through areas with high organic nitrogen (Org-N), total phosphorus (T-P), PO4-P and suspended solids (SS) concentrations and low dissolved oxygen (DO). P. arundinacea shoots grow better in deep mud and high SS and T-P, all of which were strongly correlated with slower stream currents. Accordingly, although the concentration of total nitrogen constantly increased from 1985 to 1998, the determining nutrient for the expansion of the Phalaris community and P. arundinacea shoot growth stimulation was phosphorus rather than nitrogen. The Phalaris community increased rapidly between 1991 and 1996, when brief but prominent loadings of phosphorus were observed. We concluded that the Phalaris community was restricted due to phosphorus deficiency under nitrogen excess until 1991 and subsequently rapidly expanded over the channel due to the temporary excess phosphorus present during this period. Thereafter, the rapid expansion of the Phalaris community was maintained by the clogging effect of the floating mats formed by shoots and their remains of P. arundinacea, which results in slower currents. A slower current resulted in low DO, the sedimentation of degraded plant remains (high Org-N), and the adsorption of phosphorus by suspended matter (high SS and T-P). The anaerobic conditions caused by low oxygen and the accumulation of decomposable organic matter ensure the continuous development of the Phalaris community through the release of soluble phosphorus from the sediment. © 2010 The Japanese Society of Limnology. Source

Fujii Y.,Hokkaido University | Kumakura S.,Docon Co. | Kaneko K.,H RISE
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014

Post-failure consolidation was carried out on Kimachi sandstone, Toyotomi siliceous mudstone and Inada granite to clarify whether the increased hydraulic conductivity due to failure decreased by post-failure consolidation or not. The hydraulic conductivity of post-failure consolidated rocks were 0.3-0.6 times that before post-failure consolidation and 0.9-1.5 times that before failure for Kimachi sandstone and the ratios were 0.4 times and 0.6 times for Toyotomi siliceous mudstone. On the other hand, the ratio was 0.2 times and 16 times for Inada granite. Namely, the phenomenon in which the increased hydraulic conductivity decreases by post-failure consolidation was obviously confirmed for the clastic rocks and was confirmed at some degree for the crystalline rock. The dominating mechanisms of decrease in hydraulic conductivity due to the post-failure consolidations were considered to be closure of rupture plane by crushing of mineral particles and irrecoverable closure of microcracks and elliptic pores in intact rock matrix due to plastic deformation for Kimachi sandstone, time-dependent closure of rupture plane due to visco-plastic deformation and visco-plastic pore collapse in intact rock matrix for Toyotomi siliceous mudstone, and a little visco-plastic deformation and a few pressure solution at the rupture plane for Inada granite. The different mechanisms were mainly induced by the differences in strength and deformation characteristics of mineral particles and rock matrixes. © 2014 by Japanese Committee for Rock Mechanics. Source

To determine depth dependence of permeability in various geologic deposits, exponential models have often been proposed. However, spatial variability in hydraulic conductivity, K, rarely fits this trend in coarse alluvial aquifers, where complex stratigraphic sequences follow unique trends due to depositional and post-depositional processes. This paper analyzes K of alluvial-fan gravel deposits in several boreholes, and finds exponential decay in K with depth. Relatively undisturbed gravel cores obtained in the Toyohira River alluvial fan, Sapporo, Japan, are categorized by four levels of fine-sediment packing between gravel grains. Grain size is also analyzed in cores from two boreholes in the mid-fan and one in the fan-toe. Profiles of estimated conductivity, K̄, are constructed from profiles of core properties through a well-defined relation between slug-test results and core properties. Errors in K̄ are eliminated by a moving-average method, and regression analysis provides the decay exponents of K̄ with depth. Moving-average results show a similar decreasing trend in only the mid-fan above ∼30-m depth, and the decay exponent is estimated as ≈0.11 m-1, which is 10- to 1,000-fold that in consolidated rocks. A longitudinal cross section is also generated by using the profiles to establish hydrogeologic boundaries in the fan. © 2013 Springer-Verlag Berlin Heidelberg. Source

Otani N.,Tokyo City University | Sugiki N.,Docon Co. | Miyamoto K.,Tokyo City University
Transportation Research Record

Microsimulation models of land use characterize attributes of a household and its location, referred to as microdata in this study. However, methods for evaluating the goodness of fit between estimated and observed sets of agent-based microdata have not been investigated extensively. Although the attributes of a household include various items, such as the relationship with the household head and ages of the members, housing type and spatial location, number of cars owned, and income, the attributes can be classified into general categories. The objective of the present study is to develop a goodness-of-fit evaluation method for agent-based household microdata sets composed of generalized attributes. First, a distance measure between the estimated and observed microdata for each household is defined. In this definition a generalized scheme is introduced, whereby attributes are structured by the household composition, attributes of the member, and attributes of the household as a whole. The goodness of fit is measured on the basis of the minimum sum of distances for all households in the study area. The calculation cannot be carried out with just a conventional algorithm for microdata of a typical size because the number of calculations increases in proportion to the factorial (N!) of the number (N) of agents. Therefore, a genetic algorithm, especially one using symbiotic evolution, is developed to solve the problem. The effectiveness of the method in regard to accuracy and calculation feasibility is confirmed by using person trip survey data for the Sapporo metropolitan area in Japan. Source

Kodama J.-I.,Hokkaido University | Azehara T.,Docon Co. | Fukuda D.,Hokkaido University | Fujii Y.,Hokkaido University
Zairyo/Journal of the Society of Materials Science, Japan

Fracture processes of argillaceous schist and granite subjected to freeze-thaw cycles were investigated based on their deformation behaviors. It was found that argillaceous schist showed apparent anisotropy in deformation. Significant extensile strain was observed in the direction perpendicular to the cleavage plane around -3°C in freezing process on the water-saturated specimen, followed by extensile plastic strain at the end of the cycle. No apparent extension and anisotropy were found on the water-saturated specimen of granite, but decrease in contraction rate was seen at -3°C in freezing process with AE activity. The extensile plastic strain of both rocks gradually increased with the number of freeze-thaw cycles, but magnitude of the plastic strain on argillaceous schist was much greater than that of granite. These results indicate that there might be common mechanism in fracture process between both rocks, but significant differences in deterioration rate. Deterioration of argillaceous schist is much faster because fracture mainly develops by extension of well-developed cleavage in the rock. It was concluded that weak plane such as cleavage strongly affected deterioration of rocks by freeze-thaw cycle. © 2014 The Society of Materials Science, Japan. Source

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