Development of a numerical model for nitrates in groundwater in the reservoir area of the Komesu subsurface dam, Okinawa, Japan   总被引：1，自引：0，他引：1  

Shuhei Yoshimoto  Takeo Tsuchihara  Satoshi Ishida  Masayuki Imaizumi 《Environmental Earth Sciences》2013,70(5):2061-2077

A numerical model consisting of simplified equations was developed to simulate nitrate concentrations in groundwater in a reservoir area of a subsurface dam in a Quaternary limestone region. The model was composed of a water balance sub-model and a nitrogen balance sub-model; the water balance sub-model was built from tank models which can express the quick dilution near caves and the effect of dam construction; and the nitrogen balance sub-model was made to represent changes in nitrogen forms and movement of nitrogen in the soil and aquifer zones. The model was calibrated and verified by observed data before and after the dam construction and then applied to a predictive simulation under a simple assumption that rainfall descends gradually. The model seemed applicable to long-term prediction of changes in NO₃-N in the reservoir area.  相似文献   

Mineral chemistry of MUSES‐C Regio inferred from analysis of dust particles collected from the first‐ and second‐touchdown sites on asteroid Itokawa     

Tomoki Nakamura  Aiko Nakato  Hatsumi Ishida  Shigeru Wakita  Takaaki Noguchi  Michael E. Zolensky  Masahiko Tanaka  Makoto Kimura  Akira Tshuchiyama  Toshihiro Ogami  Takahito Hashimoto  Mitsuru Konno  Masayuki Uesugi  Toru Yada  Kei Shirai  Akio Fujimura  Ryuji Okazaki  Scott. A. Sandford  Yukihiro Ishibashi  Masanao Abe  Tatsuaki Okada  Munetaka Ueno  Junichiro Kawaguchi 《Meteoritics & planetary science》2014,49(2):215-227

The mineralogy and mineral chemistry of Itokawa dust particles captured during the first and second touchdowns on the MUSES‐C Regio were characterized by synchrotron‐radiation X‐ray diffraction and field‐emission electron microprobe analysis. Olivine and low‐ and high‐Ca pyroxene, plagioclase, and merrillite compositions of the first‐touchdown particles are similar to those of the second‐touchdown particles. The two touchdown sites are separated by approximately 100 meters and therefore the similarity suggests that MUSES‐C Regio is covered with dust particles of uniform mineral chemistry of LL chondrites. Quantitative compositional properties of 48 dust particles, including both first‐ and second‐touchdown samples, indicate that dust particles of MUSES‐C Regio have experienced prolonged thermal metamorphism, but they are not fully equilibrated in terms of chemical composition. This suggests that MUSES‐C particles were heated in a single asteroid at different temperatures. During slow cooling from a peak temperature of approximately 800 °C, chemical compositions of plagioclase and K‐feldspar seem to have been modified: Ab and Or contents changed during cooling, but An did not. This compositional modification is reproduced by a numerical simulation that modeled the cooling process of a 50 km sized Itokawa parent asteroid. After cooling, some particles have been heavily impacted and heated, which resulted in heterogeneous distributions of Na and K within plagioclase crystals. Impact‐induced chemical modification of plagioclase was verified by a comparison to a shock vein in the Kilabo LL6 ordinary chondrite where Na‐K distributions of plagioclase have been disturbed.  相似文献   

Space weathered rims found on the surfaces of the Itokawa dust particles     

Takaaki Noguchi  Makoto Kimura  Takahito Hashimoto  Mitsuru Konno  Tomoki Nakamura  Michael E. Zolensky  Ryuji Okazaki  Masahiko Tanaka  Akira Tsuchiyama  Aiko Nakato  Toshinori Ogami  Hatsumi Ishida  Ryosuke Sagae  Shinichi Tsujimoto  Toru Matsumoto  Junya Matsuno  Akio Fujimura  Masanao Abe  Toru Yada  Toshifumi Mukai  Munetaka Ueno  Tatsuaki Okada  Kei Shirai  Yukihiro Ishibashi 《Meteoritics & planetary science》2014,49(2):188-214

On the basis of observations using Cs‐corrected STEM, we identified three types of surface modification probably formed by space weathering on the surfaces of Itokawa particles. They are (1) redeposition rims (2–3 nm), (2) composite rims (30–60 nm), and (3) composite vesicular rims (60–80 nm). These rims are characterized by a combination of three zones. Zone I occupies the outermost part of the surface modification, which contains elements that are not included in the unchanged substrate minerals, suggesting that this zone is composed of sputter deposits and/or impact vapor deposits originating from the surrounding minerals. Redeposition rims are composed only of Zone I and directly attaches to the unchanged minerals (Zone III). Zone I of composite and composite vesicular rims often contains nanophase (Fe,Mg)S. The composite rims and the composite vesicular rims have a two‐layered structure: a combination of Zone I and Zone II, below which Zone III exists. Zone II is the partially amorphized zone. Zone II of ferromagnesian silicates contains abundant nanophase Fe. Radiation‐induced segregation and in situ reduction are the most plausible mechanisms to form nanophase Fe in Zone II. Their lattice fringes indicate that they contain metallic iron, which probably causes the reddening of the reflectance spectra of Itokawa. Zone II of the composite vesicular rims contains vesicles. The vesicles in Zone II were probably formed by segregation of solar wind He implanted in this zone. The textures strongly suggest that solar wind irradiation damage and implantation are the major causes of surface modification and space weathering on Itokawa.  相似文献   

The first confirmed Perseid lunar impact flash     

Masahisa Yanagisawa  Kouji Ohnishi  Hiroshi Masuda  Miyoshi Ida  Masayuki Ishida 《Icarus》2006,182(2):489-495

The first confirmed lunar impact flash due to a non-Leonid meteoroid is reported. The observed Perseid meteoroid impact occurred at 18^h28^m27^s on August 11, 2004 (UT). The selenographic coordinates of the lunar impact flash are 48±1° N and 72±2° E, and the flash had a visual magnitude of ca. 9.5 with duration of about 1/30 s. The mass of the impactor is estimated to have been 12 g based on a nominal model with conversion efficiency from kinetic to optical energy of 2×¹⁰⁻³. Extrapolation of a power law size-frequency distribution fitting the sub-centimeter Perseid meteoric particles to large meteoroids suggests that several flashes should have been observed at this optical efficiency. The detection of only one flash may indicate that the optical efficiency for Perseid lunar impact is much lower, or that the slope of the size distribution differs between large meteoroids and typical sub-centimeter meteoric particles.  相似文献   

Mesoscale spatial and temporal variability of meteorological observations from an array of buoys in JASIN-1978     

Hiroshi Ishida 《Boundary-Layer Meteorology》1986,37(1-2):149-165

Observations of wind speed and direction, air and sea temperatures and solar radiation were obtained from an array of buoys in JASIN-1978 conducted in the area northwest of Scotland in the summer of 1978. The observations were analyzed to show spatial and temporal variability in the mesoscale fields. Spectra of wind speed and air and sea temperatures were computed to illustrate the distribution of variance over periods ranging from 3.5 min to 40 days. When plotted on log-log graphs, the spectral estimates generally decreased with slopes between –3/2 and –2 with increasing frequency. Spectra of air and sea temperatures had a peak at the diurnal period but not the wind speed spectrum. When plotted in variance-preserving form, the spectrum of wind speed was consistent with a spectral gap and was qualitatively similar to other observations of low-frequency spectra. On the basis of auto- and cross-correlation analyses, it appeared that mesoscale eddies propagated through the array of buoys with the mean wind speed except during times of frontal passages. The cross-correlation between wind speed and air temperature showed evidence of horizontal roll vortices or some other forms of organized convection.  相似文献   

Determination of the size distribution of polydisperse submicron aerosols by a response matrix method     

Yukimasa Ikebe 《Pure and Applied Geophysics》1972,98(1):197-212

Summary An analytical method for determining the size distribution of polydisperse submicron aerosols are described. It is shown that we can determine approximately the size distribution function analyzingZ(Q) (dependence of the aerosol concentration at the exit of a diffusion battery upon the flow rate) by a iterative technique using response matrixes. Numerical experiments were carried out to evaluate the practical application and limitations of this technique, and the technique was found to be useful itZ(Q) may be determined within the errors of about ±5 percents. Practical measurements of atmospheric submicron aerosols were made on the university campus and some examples of the size distributions of aerosols determined by this method were shown.  相似文献   

The spectroscopic study of astrometric binaries     

Goro Ishida 《Astrophysics and Space Science》1985,110(1):161-162

The spectroscopic observations of several astrometric binaries, obtained by the author during the past 20 years, are described. Main emphasis is placed on the determination of orbital elements of visual binaries, and the detection of unseen companions.Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846).  相似文献   

The absence of apparent correlations between iras and optical spectral features of late-type stars     

M. Othman  K. Ishida  S. Okamura  S. Nishimura 《Astrophysics and Space Science》1988,148(2):191-198

The spectral signatures of circumstellar dust shells (CS) of late-type stars cannot be tied in a simple manner to their optical spectral features. The spectral indices of featureless low-resolution spectrometer (LRS) spectra of K and early-M (M0-M5) stars are consistent with that of the Rayleigh-Jeans law and those of late-M (M6 and later) stars tend to have lower values showing CS radiation. There is no correlation observed between the optical sub-type and the 10 m emission strength for M stars. The absence of a simple relationship is also evident for C stars where the temperature and abundance indices show no correlation with the 11 m emission strength. The sample is confined to the IRC stars identified with accurate spectra observed by the LRS of IRAS. The IRC stars are the whole sky survey done with the 2 m band, where late-type stars are bright and interstellar extinction is one-tenth of the visual colour band.  相似文献   

Effect of Injected Water on Hydraulic Fracturing Deduced from Acoustic Emission Monitoring     

T. Ishida  Q. Chen  Y. Mizuta 《Pure and Applied Geophysics》1997,150(3-4):627-646

—In order to investigate the effects of injected water in hydraulic fracturing, experiments were conducted on cubic granite specimens, comparing fracturings induced by conventional water injection with those induced by pressurization of a urethane sleeve, thereby realizing "hydraulic fracturing" without the use of fracturing fluid. In both experiments, a shear type mechanism was found to be dominant in fault plane solutions of AE events. However, in the case of water injection, cracks extended rapidly with large drops in hole water pressure and bursts of AE, whereas in pressurization by the urethane sleeve, cracks extended stepwise with no such large drops in hole pressure and no bursts of AE. The difference in crack extension in the two experiments can be analyzed by comparing relations between crack length and stress intensity factor of mode I at a crack tip. The observation and analysis indicate that existence of fracturing fluid like water helps initiated cracks to extend rapidly and widely in hydraulic fracturing in actual HDR fields. Received September 12, 1996, accepted January 24, 1997  相似文献   

The effect of artificial viscosity on a hydrodynamic model of Cepheids     

Takeuti  Ishida  & Tanaka 《Monthly notices of the Royal Astronomical Society》1998,294(2):224-228

The effect of artificial viscosity on a hydrodynamic simulation of stellar radial pulsation is examined for the purpose of studying the dependence of the modal coupling on the sharpness of the shock front. The model used in our study is a 2.5-d first-overtone pulsator in the Cepheid instability strip. By increasing the parameters in the von Neumann–Richtmyer formula of artificial viscosity, we obtained a low growth rate together with a small pulsation amplitude. The time-scale related to pulsation mode-switching is also increased.  相似文献