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301.
Complex resistivity of mineral rocks in the context of the generalised effective‐medium theory of the induced polarisation effect
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This paper develops the generalised effective‐medium theory of induced polarisation for rock models with elliptical grains and applies this theory to studying the complex resistivity of typical mineral rocks. We first demonstrate that the developed generalised effective‐medium theory of induced polarisation model can correctly represent the induced polarisation phenomenon in multiphase artificial rock samples manufactured using pyrite and magnetite particles. We have also collected representative rock samples from the Cu–Au deposit in Mongolia and subjected them to mineralogical analysis using Quantitative Evaluation of Minerals by Scanning Electron Microscopy technology. The electrical properties of the same samples were determined using laboratory complex resistivity measurements. As a result, we have established relationships between the mineral composition of the rocks, determined using Quantitative Evaluation of Minerals by Scanning Electron Microscopy analysis, and the parameters of the generalised effective‐medium theory of induced polarisation model defined from the laboratory measurements of the electrical properties of the rocks. These relationships open the possibility for remote estimation of types of mineralisation and for mineral discrimination using spectral induced polarization data. 相似文献
302.
To understand the sedimentary development of the Boso Forearc Basin, central Japan, since ~ 3 Ma, we investigated paleothermal structure and consolidation trends in the central and eastern parts of the forearc basin through vitrinite reflectance measurements and consolidation tests. Vitrinite reflectance (Rm) was in the range 0.33 % to 0.61 % for the Miura Group in the central part of the forearc basin and 0.34 % to 0.41 % for the Miura and Kazusa Groups in the eastern. These values suggest a roughly uniform vitrinite reflectance for the Miura Group from the central to eastern parts. No significant vitrinite reflectance difference is observed across the ~ 3 Ma Kurotaki Unconformity in the eastern part of the basin. The consolidation yield stress (pc) was calculated as 27.5 MPa and 32.2 MPa for the Kiyosumi and Amatsu Formations of the Miura Group in the eastern part, respectively. Both the pc values are consistent quantitatively with represent the trend of the maximum overburden pressure estimated from the thickness and density of overlying sediments, and the difference in pc is expected by the maximum burial depths of the strata at the sampling localities. Values of pc in the eastern part of the basin increase with thickness of overlying sediment, showing no break across the Kurotaki Unconformity. Considering the eroded thickness of the Miura Group, the continuous trends in vitrinite reflectance and consolidation between the Miura and Kazusa Groups in the eastern part reflect the greater deposition of the eastern part of the Boso Forearc Basin since ~ 2.3 Ma. 相似文献
303.
We developed an ageing methodology and examined age composition of three flatfish stocks inhabiting the Seto Inland Sea, Japan. Ages were difficult to determine for three-lined tongue sole (Cynoglossus abbreviates) and ridged-eye flounder (Pleuronichthys cornutus) because the first year annulus ring was often indistinct; therefore, we used directional change in otolith growth to distinguish it. Sectioning and etching methods were powerful tools for identifying annual checks for red tongue sole (Cynoglossus joyneri). Using these ageing methods, we determined age–length relationships and growth curves. The age composition of the populations studied and of the landings showed that a large proportion of the latter consisted of individuals under the mean age of sexual maturity, thereby reducing the percent spawning potential ratio (%SPR) to ≈ 20% for all species. These findings suggest that fishing pressure on immature fish is leading to overfishing of these flatfish stocks. 相似文献
304.
Masateru Ishiguro Ryosuke Nakamura Naru Hirata Etsuko Nemoto Yuta Higuchi Aya Yamamoto Yasuhiro Yokota Tatsuaki Hashimoto 《Icarus》2010,207(2):714-1001
The Hayabusa Spacecraft Asteroid Multi-band Imaging Camera (AMICA) has acquired more than 1400 multispectral and high-resolution images of its target asteroid, 25143 Itokawa, since late August 2005. In this paper, we summarize the design and performance of AMICA. In addition, we describe the calibration methods, assumptions, and models, based on measurements. Major calibration steps include corrections for linearity and modeling and subtraction of bias, dark current, read-out smear, and pixel-to-pixel responsivity variations. AMICA v-band data were calibrated to radiance using in-flight stellar observations. The other band data were calibrated to reflectance by comparing them to ground-based observations to avoid the uncertainty of the solar irradiation in those bands. We found that the AMICA signal was linear with respect to the input signal to an accuracy of ?1% when the signal level was <3800 DN. We verified that the absolute radiance calibration of the AMICA v-band (0.55 μm) was accurate to 4% or less, the accuracy of the disk-integrated spectra with respect to the AMICA v-band was about 1%, and the pixel-to-pixel responsivity (flat-field) variation was 3% or less. The uncertainty in background zero level was 5 DN. From wide-band observations of star clusters, we found that the AMICA optics have an effective focal length of 120.80 ± 0.03 mm, yielding a field-of-view (FOV) of 5.83° × 5.69°. The resulting geometric distortion model was accurate to within a third of a pixel. We demonstrated an image-restoration technique using the point-spread functions of stars, and confirmed that the technique functions well in all loss-less images. An artifact not corrected by this calibration is scattered light associated with bright disks in the FOV. 相似文献
305.
Aya Sakaguchi Masayoshi Yamamoto Junpei Tomita Kenta Mino Keiichi Sasaki Kenji Kashiwaya Takayoshi Kawai 《Quaternary International》2009,205(1-2):65
Uranium and thorium isotopes in an 81-m long sediment core (HDP-04) of Lake Hovsgol, Mongolia, were measured to investigate their downcore distributions and to explore potential linkage to paleoenvironmental changes. Three-dimensional isochron techniques using isotope-ratio diagrams in 238U–234U–230Th–232Th system presented by Ludwig and Titterington were applied to age date the lake sediments at the depths of 11.42, 14.71 and 14.83 m in the HDP-04 section, the estimated ages of these horizons are 66 ± 8, 122 ± 11 and 128 ± 22 ka, respectively. The 238U concentration throughout the entire section fluctuated by a factor of 12, ranging from 19.9 to 232.1 mBq/g with anomalously high 238U peak at 23.8 m in depth, while the 232Th concentration varied only by a factor of about two between 24.3 and 54.0 mBq/g. The discrimination of the bulk 238U into authigenic and terrigenous 238U fractions was attempted, based on the measured 232Th as a correction index for terrigenous materials. In the upper 24 m corresponding to the last 250 ka, the authigenic 238U was higher in interglacials and lower in glacials. This depth profile of authigenic 238U contents was almost identical pattern with that found in a sediment core (VER98-1-6) from the Academician Ridge, Lake Baikal. Further, this profile can be correlated well with that of photosynthetic pigment contents, one of proxies of paleoproductivity, suggesting that the variation of authigenic 238U contents were associated with the environmental change around Lake Hovsgol. 相似文献
306.
The Iwate–Miyagi Nairiku Earthquake in 2008, whose seismic intensity was M. 7.2 in Japan Meteorological Agency (JMA) scale,
induced innumerable landslides on the southern flank of Mt. Kurikoma volcano allocated along the Ou Backbone Range in Northeast
Japan. Most landslides are detected in a hanging wall side of the seismic fault. Those landslides are classified into five
types: deep-seated slide, debris slide, shallow debris slide, secondary shallow debris slide, and debris flow. Most common
landslide types induced by the earthquake are shallow debris slides and subsequent debris flows. They are intensively distributed
along steep gorges incising a volcanic skirt of Mt. Kurikoma, consisting of welded ignimbrite of the Pleistocene age. Debris
flows are also distributed even along gentle river floors in the southern lower flank of the volcano. The area of densely
distributed debris slides, shallow debris slides, and debris flows is concordant with that of severe seismic tremor. Thus,
genetic processes of landslides induced by the Iwate–Miyagi Nairiku Earthquake in 2008 are attributed to multiple causative
factors such as geology, topography, and seismic force. 相似文献
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310.
This paper presents a finite element model for analysing the behaviour of granular material wrapped with polyethylene bags under vertical compression and cyclic shearing. The simple Mohr–Coulomb model is used to represent the soil behaviour. The polyethylene bag is represented by a linear-elastic–perfect-plastic model. The soil-bag interface is modelled with contact constraints. The main purpose of the numerical analysis is to validate the anticipated performance of soilbags under various loading conditions and hence the effectiveness of soilbags as a method of ground improvement. 相似文献