The size distribution of urban blocks is important for the characterisation of urban block patterns and is known to follow several parametric statistical distributions. However, it has not previously been analysed on the basis of a normative plane tessellation and in terms of urban block density and mean road width. In this article, we formulate the size distribution of Voronoi cells using the gamma distribution estimated by urban block density and mean road width. We found that (1) both log-normal and gamma distributions can be good candidates for the size distribution of urban blocks at the scale of a region that consists of regular urban blocks and that has a uniform road width; and (2) the size distribution of urban blocks depends on the balance between pattern and width improvement effects. Based on one study region in Tokyo, if the pattern improvement effect is more prominent than the width improvement effect, the mode of urban block sizes tends to be larger than if it is not. These findings are expected to provide scientific support for urban planning (e.g. land readjustment projects). 相似文献
The reversibility of the temperature effect on the chemical composition of interstitial waters of three deep-sea sediment samples was examined between 2 and 25°C for Cl, Na, K, Mg, Ca, Si, B, Mn and alkalinity. When the temperature of sediment samples was returned from 25°C to the initial value of 2°C, most chemical species gave nearly their initial concentrations. However, for alkalinity and in one case for magnesium, it took another three to four hours to reach their initial concentrations. 相似文献
Three High Frequency (HF) ocean radar stations were installed around the Soya/La Perouse Strait in the Sea of Okhotsk in order
to monitor the Soya Warm Current (SWC). The frequency of the HF radar is 13.9 MHz, and the range and azimuth resolutions are
3 km and 5 deg., respectively. The radar covers a range of approximately 70 km from the coast. The surface current velocity
observed by the HF radars was compared with data from drifting buoys and shipboard Acoustic Doppler Current Profilers (ADCPs).
The current velocity derived from the HF radars shows good agreement with that observed using the drifting buoys. The root-mean-square
(rms) differences were found to be less than 20 cm s−1 for the zonal and meridional components in the buoy comparison. The observed current velocity was also found to exhibit reasonable
agreement with the shipboard ADCP data. It was shown that the HF radars clearly capture seasonal and short-term variations
of the SWC. The velocity of the Soya Warm Current reaches its maximum, approximately 1 m s−1, in summer and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately
40 km. The surface transport by the SWC shows a significant correlation with the sea level difference along the strait, as
derived from coastal tide gauge records at Wakkanai and Abashiri.
Deceased. 相似文献
Vertical distributions of sulfate, hydrogen sulfide, and iron (II) concentrations in interstitial waters and of sulfur content in sediment have been studied in a sediment core (73 cm long) from a meromictic lake, Lake Suigetsu, which changed from fresh-water to brackish conditions in 1664 A.D. The diatom assemblage of the sediment has also been analyzed. A boundary between high (>1.5%) and low (<0.2%) sulfur contents is found at a depth of 52 cm in the core. In the high sulfur layer (above 52 cm), the maximum sulfur content is 6.8% at 35 to 37 cm. The diatom assemblage, however, indicates that the boundary between fresh-water and brackish sediments lies at 40 cm. The hydrogen sulfide and iron (II) profiles in the interstitial waters indicate a sink for these chemical species near a depth of 40 cm. The discrepancy between the chemically-defined boundary at 52 cm and the paleontologically-defined boundary at 40 cm seems to be due to the downward migration of hydrogen sulfide and deposition of iron sulfide after the lake became brackish. 相似文献
Vertical profiles of manganese concentration in interstitial waters and of manganese and iron contents in five chemically-separated fractions of sediments have been studied in a sediment core (73 cm long) from a meromictic lake, Lake Suigetsu, which changed from freshwater to brackish conditions in 1664 A.D. The interstitial waters show a minimum manganese concentration of 0.13 ppm near a depth of 10 cm and a maximum of 26 ppm near 65 cm in the core. A predominant amount of manganese, up to 0.17%, is found in the hydrogen peroxide-soluble fraction of sediments in layers above a depth of 52 cm. It is suggested that the manganese is included in stable iron sulfides such as pyrite. Manganese, which diffuses upward from the lower layer, is thought to be deposited along with stable iron sulfide during diagenetic formation of the latter near a depth of 10 cm in the core. 相似文献
To understand the behavior of manganese in diagenetic processes in sediments of an enclosed bay which is similar to those
of an estuary, chemical analyses have been carried out on both sediment and interstitial water of a core sample collected
from Tokyo Bay. The results suggest that redistribution of manganese takes place within the sediment as a result of the dissolution
of buried manganese oxides and hydroxides under reducing condition, the downward diffusion of Mn2+ through the interstitial water toward lower layers and then the precipitation of carbonate. The carbonate formed in the sediment
contains managanese carbonate probably as a solid solution between calcitic calcium carbonate and manganese carbonate. 相似文献
The vertical structure of the Soya Warm Current (SWC) was observed by a bottom-mounted acoustic Doppler current profiler (ADCP)
in the region of the SWC axis near the Soya Strait during a 1-year period from May 2004. The ADCP data revealed a marked seasonal
variability in the vertical structure, with positive (negative) vertical shear in summer and fall (winter and spring). The
volume transport of the SWC is estimated on the basis of both the vertical structure observed by the ADCP and horizontal structure
observed by the ocean radars near the strait. The transport estimates have a minimum in winter and a maximum in fall, with
the yearly-averaged values in the range of 0.94–1.04 Sv (1 Sv = 106 m3 s−1). These lie within a reasonable range in comparison to those through other straits in the Japan Sea. 相似文献
Recently much attention is focussed on the problems of global warming due to greenhouse effect gases, notably carbon dioxide and methane. Because these gases cause important problems to the global environment, their generation from landfill sites containing solid wastes has drawn attention and their environmental impact is causing concern.
Generally, the gases associated with a greenhouse effect include carbon dioxide, methane and nitrous oxide. However, there are no general basic data available concerning gases generated from biodegradation of solid wastes in landfill sites. Specifically, no assessment has been made concerning greenhouse effect gases from different landfill types.
This paper proposes a quantitative model for estimating the gasification rate by different landfill types. The model is based on measurement data for a long-term material balance for an aerobic landfill and an anaerobic landfill, obtained with two types of large-scale lysimeters.
This paper will also give an estimate for the amount of greenhouse effect gases by for different types of landfill and propose countermeasures for their reduction. 相似文献
Kyushu Island, Japan, is located at the junction of the Southwest Japan arc and the Ryukyu arc. There are two major late Cenozoic
epithermal gold-silver provinces in Kyushu, which are termed the Northern and Southern provinces. The provinces are characterized
by: 1) Pliocene volcanism dominated by calc-alkaline andesite, followed by Quaternary volcanism including extrusion of both
calc-alkaline and tholeiitic magmas; 2) formation of extensional grabens; 3) Pliocene to Pleistocene mineralization, which
was dominated by abundant low sulfidation (LS) epithermal deposits with a few high sulfidation (HS) examples. The two epithermal
gold-silver provinces have evolved differently since about 5 Ma; the Northern province has exhibited diminished hydrothermal
activity from the Pliocene to Pleistocene, whereas the Southern province has witnessed increased hydrothermal activity mainly
in easterly and northerly directions. Changes of tectonic setting from the Pliocene to Pleistocene account for the variable
trends in epithermal gold deposit formation. Westward oblique subduction of the Philippine Sea plate beneath the Southwest
Japan arc caused development of the Hohi graben and arc-related volcanism at about 6 Ma. This was associated with widespread
LS mineralization in and surrounding the Hohi graben, as is represented by the Bajo and Taio deposits. The subduction of the
relatively buoyant Kyushu-Palau ridge during the early Pliocene strengthened the coupling between the slab and overriding
Ryukyu arc, leading to polygenetic andesite volcanism with associated HS (Kasuga, Iwato, and Akeshi) and LS (Kushikino) mineral
deposits forming in the Southern province. A change of the subduction direction of the Philippine Sea plate, from west to
north-northwest in the early Pliocene, increased the orthogonal convergence rate between the Southwest Japan arc and the Philippine
Sea plate, resulting in a decrease of volcanic and hydrothermal activity in the Hohi graben of the Northern province. The
more northerly subduction of the Philippine Sea plate shifted the locus of the Kyushu-Palau ridge subduction northward, resulting
in underplating of the older (85–60 Ma), negatively buoyant Amami basin oceanic slab in the Southern province, rather than
continued subduction of the young (27–15 Ma), buoyant Shikoku basin slab. This replacement caused steepening of the slab angle
and slab-rollback in the Southern province, which was associated with regional extension, an eastward shift of the Ryukyu
volcanic front, and development of the Kagoshima and Shimabara grabens, as well as the Okinawa trough. Rhyolite and basalt
volcanism, in addition to andesite volcanism, have occurred since 2 Ma in the area of the Ryukyu back arc; coincident LS mineralization
at Hishikari and Ohkuchi was affiliated with the rhyolite volcanism. Another change of the subduction direction of the Philippine
Sea plate to the northwest occurred at 2–1 Ma. The forearc sliver of the Southwest Japan arc shifted westward, in association
with right-lateral strike-slip faulting along the Median tectonic line, due to the increase of the westward convergence rate.
This shift resulted in shortening and cessation of graben development in the Hohi area, restricting the subsequent volcanism
and related hydrothermal activity to the central part of the graben. 相似文献