Electronic Transports for Thermoelectric Applications on IVVI Semiconductors

Seebeck effect, Peltier effect, Thomson effect, electronic thermal conductivity, Hall effect, and Nernst effect are described on the basis of electronic conduction theory, taking account of effective mass anisotropy, nonparabolicity in Ek relation, and temperature dependent band gap. It is shown that the temperature dependence of the band gap does not modify the basic equations for the Seebeck coefficient, thermal conductivity, and Nernst coefficient. In narrow gap semiconductors, existence of minority carriers significantly enhances the electronic thermal conductivity, owing to the multiple carrier transport known as bipolar diffusion. Calibration coefficient £ for the Hall effect (R H ¼ À£=en) is increased by nonparabolicity in the Ek relation. Nernst coefficient gives useful information on scattering properties of the materials

Effects of floodplain structure on the dynamics of riparian forests in a mountainous region of central japan

This study clarified relationships between floodplain structure and riparian vegetation patterns, and examined effects of levee construction on vegetation dynamics in the Kamikochi Valley, central Japan. Development of riparian forests was controlled by the width of the floodplain, which was reduced by alluvial and talus cones from tributary basins. The disturbance regime in riparian forests was influenced by the width of the floodplain. Riparian forest stands were frequently replaced by young stands in river sections with a narrow floodplain, whereas forests were mosaics of different stand ages, including mature trees, in river sections with a wide floodplain. Levee construction on the floodplains altered the disturbance regime, reducing and degrading Chosenia arbutifolia habitats. Such long-term effects of artificial levees should be considered in river management plans

Spatial change in tree utilization on the northeastern slope of mount kenya

Spatial change in tree utilization in the Central Meru District, which is located on the northeastern slopes at the foot of Mt. Kenya was investigated. This paper outlines the distribution and utilization of various indigenous trees. Muringa (Cordia africana) was found to be the most useful tree in this region. Its habitat had the widest range of humidity, and it was used for the widest range of purposes. The diversity of indigenous trees utilized did not increase with humidity. A wider variety of indigenous trees were used on the dry, lower slopes than on the humid, upper slopes. A sacred tree, Mutero (Olea europaes spp. africana) was the second most useful tree. It was used for charcoal and firewood. Most inhabitants held no traditional respect for the sacred tree, suggesting that traditional values and practices with respect to some trees have changed

Influences of bedrock and landforms on forest-line formation on a volcanic mountain in southwestern japan

The structure and causal factors of a forest line, the boundary between mountainous forests and non-forest vegetation, were studied on Mt. Daisen, Japan, to clarify the long-term influences of volcanic evolution on vegetation. A distinct forest line formed at between 1100 and 1300 m elevation, which coincided with the geological boundary of the lava dome and talus deposits. No forest stands were able to develop on the summit lava dome because of poor soil development, and the position of the forest line was controlled not by macroclimatic or topoclimatic conditions but rather by the immature soils on the lava dome that formed during the late Pleistocene to early Holocene

A preliminary study on the effects of pyroclastic fall deposit on the forest ecosystem in southwestern hokkaido, japan

In southwestern Hokkaido, volcanic activities were high during historical times. For examination of their effects on forest ecosystem, we conducted preliminary survey using a dendroecological technique. Tree-ring samples were collected mainly in the southern part of the Ishikari Lowland where some layers of pyroclastic fall were found. The number of tree-rings was counted and tree-ring widths were measured. As a result, we could distinguish from the 1739 tree ring measurements the effect of eruption with its subsequent Ta-a volcanic deposition. This proves that the effect on tree growth changed in proportion to distance from the origin of the pyroclastic fall

Landform effects on tree size in reestablished forests after fires

The spatial heterogeneity of tree size in stands recovered after fires was examined in a 5m×110m belt transect and 150 plots in the Teshio Experiment Forest situated in northern Japan. Tree growth in the reestablished stands was affected by topographic conditions. Canopy height and maximum DBH varied with slope aspect, topographic position, and elevation as well as stand age. They were found to be small 1) on southeast-, south-, southwest-, and west-facing slopes, 2) on ridges, upper parts of slopes, and terrace surfaces, and 3) within high-elevation zones. The effects of ultramafic soil from serpentinized rock on tree size were smaller than those of the topographic conditions. It follows from these findings on reestablished communities that prevailing southwesterly winds are importantly involved in regeneration