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排序方式: 共有583条查询结果,搜索用时 31 毫秒
31.
Hiroaki Sasaki Akihiko Tanaka Mitsunori Iwataki Yasuharu Touke Eko Siswanto Chun Knee Tan Joji Ishizaka 《Journal of Oceanography》2008,64(4):511-523
Remote sensing reflectance [R
rs(λ)] and absorption coefficients of red tides were measured in Isahaya Bay, southwestern Japan, to investigate differences in
the optical properties of red tide and non-red tide waters. We defined colored areas of the sea surface, visualized from shipboard,
as “red tides”. Peaks of the R
rs(λ) spectra of non-red tide waters were at 565 nm, while those of red tides shifted to longer wavelengths (589 nm). The spectral
shape of R
rs(λ) was close to that of the reciprocal of the total absorption coefficient [1/a(λ)], implying that the R
rs(λ) peak is determined by absorption. Absorption coefficients of phytoplankton [a
ph(λ)], non-pigment particles and colored dissolved organic matter increased with increasing chlorophyll a concentration (Chl a), and those coefficients were correlated with Chl a for both red tide and non-red tide waters. Using these relationships between absorption coefficients and Chl a, variation in the spectrum of 1/a(λ) as a function of Chl a was calculated. The peak of 1/a(λ) shifted to longer wavelengths with increasing Chl a. Furthermore, the relative contribution of a
ph(λ) to the total absorption in red tide water was significantly higher than in non-red tide water in the wavelength range 550–600
nm, including the peak. Our results show that the variation of a
ph(λ) with Chl a dominates the behavior of the R
rs(λ) peak, and utilization of R
rs(λ) peaks at 589 and 565 nm may be useful to discriminate between red tide and non-red tide waters by remote sensing. 相似文献
32.
Nguyen Ba Thuy Katsutoshi Tanimoto Norio Tanaka Kenji Harada Kosuke Iimura 《Ocean Engineering》2009,36(15-16):1258-1269
The objective of this study is to investigate the effects of an open gap, such as a road, in a coastal forest on tsunami run-up. A numerical model based on two-dimensional nonlinear long-wave equations was developed to account for the effects of drag and turbulence induced shear forces due to the presence of vegetation. Experiments were conducted on a forest simulated with vertical cylinders by changing the gap width. The numerical model was validated in good agreement with the experimental results. The numerical model was then applied to a wide forest of Pandanus odoratissimus, a tree species that is a dominant coastal vegetation on a sand dune in South and Southeast Asia. The effect of vertical stand characteristics of P. odoratissimus with aerial roots was considered on the drag resistance. A straight open gap perpendicular to the shoreline was used to investigate the effect of gap width. As the gap width increases, the flow velocity at the end of the open gap first increases, reaches a maximum, and then decreases, while the run-up height increases monotonously. The maximum velocity in the present condition is 1.7 times the maximum velocity without a coastal forest. The effects of different gap arrangements in the forest on tsunami run-up were also investigated in this paper. The flow velocity at the end of an open gap can be reduced by a staggered arrangement. 相似文献
33.
Tadashi Akamatsu Kiyoshi Fujino Mineo Kumazawa Akio Fujimura Manabu Kato Hiroshi Sawamoto Takamitsu Yamanaka 《Physics and Chemistry of Minerals》1988,16(2):105-113
Synthetic (Mg0.51, Mn0.49)2SiO4 olivine samples are heat-treated at three different pressures; 0, 8 and 12 GPa, all at the same temperature (~500° C). X-ray structure analyses on these single crystals are made in order to see the pressure effect on cation distribution. The intersite distribution coefficient of Mg and Mn in M1 and M2 sites, K D = (Mn/Mg) M1/(Mn/Mg) M2, of these samples are 0.192 (0 GPa), 0.246 (8 GPa) and 0.281 (12 GPa), indicating cationic disordering with pressure. The small differences of cell dimensions between these samples are determined by powder X-ray diffraction. Cell dimensions b and c decrease, whereas a increases with pressure of equilibration. Cell volume decreases with pressure as a result of a large contraction of the b cell dimension. The effect of pressure on the free energy of the cation exchange reaction is evaluated by the observed relation between the cell volume and the site occupancy numbers. The magnitude of the pressure effect on cation distribution is only a fifth of that predicted from the observed change in volume combined with thermodynamic theory. This phenomenon is attributed to nonideality in this solid solution, and nonideal parameters are required to describe cation distribution determined in the present and previous experiments. We use a five-parameter equation to specify the cationic equilibrium on the basic of thermodynamic theory. It includes one energy parameter of ideal mixing, two parameters for nonideal effects, one volume parameter, and one thermal parameter originated from the lattice vibrational energy. The present data combined with some of the existing data are used to determine the five parameters, and the cation distribution in Mg-Mn olivine is described as a function of temperature, pressure, and composition. The basic framework of describing the cationic behavior in olivine-type mineral is worked out, although the result is preliminary: each of the determined parameters is not accurate enough to enable us to make a reliable prediction. 相似文献
34.
Antiphase domains (APD's) of pigeonite lamellae in natural and heated augite crystals from the Hakonetoge andesite have been examined by a transmission electron microscope (TEM). Antiphase boundaries (APB's) of the pigeonite lamellae in natural specimens have a sigmoidal shape cutting the c axis in (010) sections. APB's in specimens heated at temperatures above the high-low inversion and then quenched are nearly parallel to the c axis with almost straight boundaries. These observations indicate that the preferred orientation of APB's in (010) sections depends on cooling rate; at fast colling rates the APB's are nearly parallel to the c axis, whereas at slower cooling rates they are inclined to the c axis. The cooling rate of the natural augite specimen from Hakonetoge is estimated to be about 0.01 °C/h from the experimentally determined time-temperature-transformation (TTT) diagram for the APB orientations. APD sizes are large in specimens quenched from above the inversion temperature; they are at a minimum after cooling rates of around 1–0.1 °C/h, and then become larger with slower cooling rates. 相似文献
35.
Detection of anomalous seismic phases by the wavelet transform 总被引:1,自引:0,他引:1
Kiyoshi Yomogida 《Geophysical Journal International》1994,116(1):119-130
36.
The chemical composition of lake water in Laguna Amarga, a small, shallow, saline lake near the Torres del Paine National Park (at 51°S), Chilean Patagonia, was studied in January, 1993. The water was strongly alkaline (pH 9.4) conductivity was 71.4 mS cm–1, and salinity was 77 g L–1. The major ions were sodium and sulphate. 相似文献
37.
Numerical study of the oxidation process of dimethylsulfide in the marine atmosphere 总被引:1,自引:0,他引:1
A box model, involving simple heterogeneous reaction processes associated with the production of non-sea-salt sulfate (nss-SO
4
2–
) particles, is used to investigate the oxidation processes of dimethylsulfide (DMS or CH3SCH3) in the marine atmosphere. The model is applied to chemical reactions in the atmospheric surface mixing layer, at intervals of 15 degrees latitude between 60° N and 60° S. Given that the addition reaction of the hydroxyl radical (OH) to the sulfur atom in the DMS molecule is faster at lower temperature than at higher temperature and that it is the predominant pathway for the production of methanesulfonic acid (MSA or CH3SO3H), the results can well explain both the increasing tendency of the molar ratio of MSA to nss-SO
4
2–
toward higher latitudes and the uniform distribution with latitude of sulfur dioxide (SO2). The predicted production rate of MSA increases with increasing latitude due to the elevated rate constant of the addition reaction at lower temperature. Since latitudinal distributions of OH concentration and DMS reaction rate with OH are opposite, a uniform production rate of SO2 is realized over the globe. The primary sink of DMS in unpolluted air is caused by the reaction with OH. Reaction of DMS with the nitrate radical (NO3) also reduces DMS concentration but it is less important compared with that of OH. Concentrations of SO2, MSA, and nss-SO
4
2–
are almost independent of NO
x
concentration and radiation field. If dimethylsulfoxide (DMSO or CH3S(O)CH3) is produced by the addition reaction and further converted to sulfuric acid (H2SO4) in an aqueous solution of cloud droplets, the oxidation process of DMSO might be important for the production of aerosol particles containing nss-SO
4
2–
at high latitudes. 相似文献
38.
39.
Glenn J. MacPherson Miryam Bar-Matthews Tsuyoshi Tanaka Edward Olsen 《Geochimica et cosmochimica acta》1983,47(4):823-839
Mineralogical and petrographic studies of a wide variety of refractory objects from the Murchison C2 chondrite have revealed for the first time melilite-rich and feldspathoid-bearing inclusions in this meteorite, but none of these is identical to any inclusion yet found in Allende. Blue spinel-hibonite spherules have textures indicating that they were once molten, and thus their SiO2-poor bulk composition requires that they were exposed to higher temperatures (>1550°C) than those deduced so far from any Allende inclusion. Melilite-rich inclusions are similar to Allende compact Type A's, but are more Al-, Ti-rich. One inclusion (MUCH-1) consists of a delicate radial aggregate of hibonite crystals surrounded by alteration products, and probably originated by direct condensation of hibonite from the solar nebular vapor. The sinuous, nodular and layered structures of another group of inclusions, spinel-pyroxene aggregates, suggest that these also originated by direct condensation from the solar nebular gas. Each type of inclusion is characterized by a different suite of alteration products and/or rim layers from all the other types, indicating modification of the inclusions in a wide range of different physico-chemical environments after their primary crystallization. All of these inclusions contain some iron-free rim phases. These could not have formed by reaction of the inclusions with fluids in the Murchison parent body because the latter would presumably have been very rich in oxidized iron. Other rim phases and alteration products could have formed at relatively low temperatures in the parent body, but some inclusions were not in the locations in which they were discovered when this took place. Some of these inclusions are too fragile to have been transported from one region to another in the parent body, indicating that low temperature alteration of these may have occurred in the solar nebula. 相似文献
40.
Kazutaka Yamaoka Yoshihiro Ueda Hajime Inoue Fumiaki Nagase Ken Ebisawa Taro Kotani Yasuo Tanaka 《Astrophysics and Space Science》2001,276(1):19-22
We summarize the ASCA observations of the two Galactic superluminal sources GRO J1655–40 and GRS 1915+105, focusing on theabsorption line features.The high spectroscopic capability of ASCA enabled us to detectiron-K absorption line features from both objects. This is direct evidence for the presence of highly ionized plasma in a non-spherical configuration around a black hole, and is considered to be a unique signature of superluminal jet systems. The candidate of the line-absorber would be a part of an accretion disk at a distance of 109-11 cm from the central X-ray source. 相似文献