Box-counting dimension of solution curves for a class of two-dimensional nonautonomous linear differential systems

A class of two-dimensional linear differential systems is considered. The box-counting dimension of the graphs of solution curves is calculated. Criteria to obtain the box-counting dimension of spirals are also established.Comment: 20 pages, 6 figure

Evasion characteristics of Plecoglossus altivelis altivelis in fish school against air bubbles in open-channel flows

The 12th International Symposium on Particle Image Velocimetery, 2017, June 18–22, Busan, Kore

Effects of spanwise width of expansion area in open-channel flow on resting characteristics of oikawa, Zacco platypus

The 12th International Symposium on Particle Image Velocimetery, 2017, June 18–22, Busan, Kore

Effects of instillation locations of boulders at bottom of pool-and-weir fishway on migration rate of Zacco platypus

It is important to keep suitable area by boulders in pooland- weir fishway to make the migration rate of fish high. In this study, migrating behaviors of Zacco platypus in pooland- weir fishway were compared with locations of boulders placed on the bottom of pool-and-weir fishway changed. Migration behaviors of Zacco platypus were obtained with the aid of two digital video cameras. It was found that Zacco platypus migrates remarkably uses the space between boulders when boulders were placed on the upper bottom in the pool. It is because the velocity of space between boulders is low compared to other space.The 11th Pacific Symposium on Flow Visualization and Image Processing, 2017, 1-3 December, Kumamoto, Japa

Effects of slopes and spaces of protrusions in fish ladder for eels on migration rate of Anguilla japonica

In recent year, populations of Anguilla japonica have been decreasing sharply. This decrease is partly because it is estimated to be overfishing of Anguilla japonica, the deterioration of the river environment and so on. Migrating fishes are impeded by weirs and dams in the river. Fishways have been constructed to swimming fish like Plecoglossus altivelis altivelis in order to solve this problem. On the other hand, it is thought that special fishway is necessary for demersal fish like eels. Furthermore, studies on fish ladder for eels haven’t been conducted. In the present study, an investigation on migration rate of Anguilla japonica was conducted under the condition that slope of fish ladder for eels and spaces of protrusions are changed. It was found that migration rates decreased with the increase of slopes and spaces of protrusions. Besides, Anguilla japonica migrated while using protrusions by serpentine movement.The 11th Pacific Symposium on Flow Visualization and Image Processing, 2017, 1-3 December, Kumamoto, Japa

Strength improvement of lime-treated clay with sodium chloride

Lime stabilisation of organic clay has often been studied in the past. However, there is some evidence in the literature that the presence of high concentrations of organic matter in clay soil can lessen the chemical reaction between lime and clay minerals and can have detrimental effects on the engineering properties of soil. Hence, in this paper, the stress–strain behaviour and strength properties of organic soil treated with lime and sodium chloride (NaCl) are analysed. A soil mixture, prepared with 5% lime content and 1·5% humic acid, was stabilised with varying quantities of sodium chloride (0·5, 2·0 and 5·0%). Consolidated undrained and drained triaxial tests were carried out on specimens at curing periods of 7 and 28 d with applied confining pressures of 50 and 100 kPa. Scanning electron microscopy and X-ray diffraction analysis were used to observe the microstructural changes resulting from cementation materials. It was found that the introduction of sodium chloride improved considerably the strength properties of the lime-treated organic clay. The microstructural analysis also confirmed the presence of calcium silicate hydrate in a salt-treated organic clay, which was the main contributing factor to the enhanced engineering properties of the clay