Accuracy of quantized Voronoi diagrams     

Yukio Sadahiro  Takashi Tominaga 《International journal of geographical information science》2013,27(10):1173-1189

Quantization of spatial objects, which usually means vector‐to‐raster conversion in GIS and remote sensing, is a basic operation used for handling spatial data from data creation to visualization. Since quantization is an approximation of spatial objects, it inevitably yields errors in measuring their properties such as area, perimeter, diameter, and so forth. This paper discusses the accuracy of a quantized Voronoi diagram, a spatial tessellation generated from a set of points. A measure is proposed to evaluate the accuracy of the area of Voronoi regions calculated after quantization. In one‐dimensional space the measure is expressed as an explicit function of the expected number of generators in a cell. In two‐dimensional space, on the other hand, the measure is defined by an implicit function, whose approximation is derived in an explicit form. These functions permit us to evaluate the accuracy of quantization in relation to the size of lattice cells and the density of Voronoi generators. This leads to an appropriate choice of a lattice to keep the quality of a quantized Voronoi diagram at a desirable level.  相似文献   

Case story: time-lapse seismic crosswell monitoring of CO₂ injected in an onshore sandstone aquifer     

Jesper Spetzler  Ziqiu Xue  Hideki Saito  Osamu Nishizawa 《Geophysical Journal International》2008,172(1):214-225

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Optical photometry and spectroscopy of the Type Ibn supernova SN 2006jc until the onset of dust formation     

G. C. Anupama  D. K. Sahu  U. K. Gurugubelli  T. P. Prabhu  N. Tominaga  M. Tanaka  K. Nomoto 《Monthly notices of the Royal Astronomical Society》2009,392(2):894-903

We present optical UBVRI photometric and spectroscopic data of the Type Ibn supernova SN 2006jc, until the onset of the dust-forming phase. The optical spectrum shows a blue continuum and is dominated by the presence of moderately narrow (velocity ∼2500 km s⁻¹) He  i emission lines superimposed over a relatively weak supernova spectrum. The helium lines are produced in a pre-existing He-rich circumstellar shell. The observed helium line fluxes indicate the circumstellar shell is dense, with a density of  ∼10⁹–10¹⁰ cm⁻³  . The helium mass in this shell is estimated to be  ≲0.07 M_⊙  . The optical light curves show a clear signature of dust formation, indicated by a sharp decrease in the magnitudes around day 50, accompanied by a reddening of the colours. The evolution of the optical light curves during the early phase and that of the uvoir bolometric light curve at all phases is reasonably similar to normal Ib/c supernovae.  相似文献   

A model for the hydrogen coma of a comet     

Yoshimi Kitamura  Osamu Ashihara  Tetsuo Yamamoto 《Icarus》1985,61(2):278-295

A model for the hydrogen coma of a comet on the basis of the Monte Carlo method is presented. In this model isotropic ejections of H atoms produced by photodissociation of H₂O and OH, thermalization of the H atoms due to collisions with ambient H₂O molecules, and the solar radiation pressure have been taken into account. A production spectrum of H atoms from OH is evaluated by using the predissociation rates and the level populations of OH, confirming that the spectrum has a sharp peak around 8.0 km sec^?1 with the standard deviation of 0.1 km sec^?1. Including the above effects, velocity distribution functions of the H atoms at various positions in the coma for the first time, as well as their density and outflow velocity profiles, have been calculated. It is pointed out that the collisional thermalization process in the inner coma is an important factor at small heliocentric distances in determining the density profiles and the velocity distributions. It is shown that thermalization leads to an increase in the H density in the inner coma larger than those expected from other models such as the vectorial model, in which collision is not taken into account. Lyman α isophotes and its line profiles in the optically thin region are computed by using the velocity distribution function.  相似文献   

Morphology of intergranular pores and wetting angles in pelitic schists studied by transmission electron microscopy   总被引：2，自引：0，他引：2  

Takehiko Hiraga  Osamu Nishikawa  Toshiro Nagase  Mizuhiko Akizuki 《Contributions to Mineralogy and Petrology》2001,141(5):613-622

In pelitic schists composed mainly of quartz and albite grains, the morphology of intergranular pores, which were filled with water, was studied by transmission electron microscopy (TEM). Although some pores are defined by crystallographic planes (F-face), most of their form has an ideal shape determined by interface tensions between grains and fluid. High-resolution TEM observations demonstrate that pore-free regions at grain boundaries are tight even at the nanometer scale, showing that the wetting angle is larger than 0° in this rock. The pore distribution in two-grain junctions can be compared to a "necklace microstructure" developed by instability of a fluid film along the boundary induced by microcracking. Wetting angles for pores located at grain edges of quartz and albite decrease in the order albite/albite, quartz/quartz, and quartz/albite. The quartz/quartz wetting angle in a calcite-free sample is smaller than that in a calcite-containing sample. This angle also changes due to grain misorientation. Our results confirm that solid-solid and solid-fluid interfacial energies control the geometry of intergranular fluid in natural rocks.  相似文献   

A Study Of The Atmospheric Boundary Layer Using Radon And Air Pollutants As Tracers     

Toshio Kataoka  Eiji Yunoki  Mitsuo Shimizu  Tadashige Mori  Osamu Tsukamoto  Yukitaka Ohashi  Ken Sahashi  Toshihiko Maitani  Koh’ichi Miyashita  Toru Iwata  Yoko Fujikawa  Akira Kudo  Roger H. Shaw 《Boundary-Layer Meteorology》2001,101(2):131-156

Concentrations of radon ²²²Rn andair pollutants, meteorological parametersnear the surface and vertical profiles of meteorological elements were measured atUchio (Okayama City, Okayama Prefecture, Japan) 12 km north from the coast ofthe Inland Sea of Japan. In the nighttime, the ²²²Rn concentration increased in the case of weak winds, but did not increase as much in the case of moderate or strong winds, as had been expected. In the daytime, the ²²²Rn concentrationheld at a slightly higher than average level for the period from sunrise to about 1100 JST. It is considered that this phenomenon is due to a period of morning calm, that is, a transition period from land breeze to sea breeze.NO, which is sensitive to traffic volume,brought information concerning advection.Oxidant concentrations,which reflect the availability of sunlight,acted in the reverse manner to ²²²Rnconcentrations. Thus, a set of ²²²Rn and air pollutants could provide useful information regarding the local conditions of the atmospheric boundary layer.  相似文献   

Rare gas isotopic compositions in natural gases of Japan     

Keisuke Nagao  Nobuo Takaoka  Osamu Matsubayashi 《Earth and Planetary Science Letters》1981,53(2):175-188

Isotopic and elemental compositions of rare gases in various types of gas samples collected in the Japanese Islands were investigated. Excess³He was found in most samples. Many samples showed a regionally uniform high³He/⁴He ratio of about 7 times the atmospheric ratio. The He concentrations varied from 0.6 to 1800 ppm, and they were low in CO₂-rich gases and high in N₂-rich gases. Ne isotopic deviations from the atmospheric Ne were detected in most volcanic gases. The deviations and the elemental abundance patterns in volcanic gases can be explained by a mixing between two components, one is mass fractionated rare gases and the other is isotopically atmospheric and is enriched in heavy rare gas elements. Ar was a mixture of mass fractionated Ar, atmospheric Ar and radiogenic Ar, and the contribution of radiogenic⁴⁰Ar was small in all samples. Except for He, elemental abundance patterns were progressively enriched in the heavier rare gases relative to the atmosphere. Several samples were highly enriched in Kr and Xe relative to the abundance pattern of dissolution equilibrium of atmospheric rare gases in water. The component which is highly enriched in heavy rare gases may be released from sedimentary materials in the crust.  相似文献   

Partition of magnesium and iron between Olivine and spinel,and between pyroxene and spinel     

Osamu Nishizawa  Syun-iti Akimoto 《Contributions to Mineralogy and Petrology》1973,41(3):217-230

Partition of Fe²⁺ and Mg between coexisting (Mg, Fe)₂SiO₄ spinel and (Mg, Fe)SiO₃ pyroxene was investigated at pressures 80 and 90 kbar and at temperatures 840 and 1050° C, using tetrahedral-anvil type of high pressure apparatus. Olivine-spinel solid solution equilibria in the system Mg₂SiO₄-Fe₂SiO₄ were discussed in the light of the partition reaction. Partition of Fe²⁺ and Mg in both olivine-spinel and pyroxene-spinel systems can not be regarded as that between ideal solid solutions. By applying the simple solution model for the partition of Fe²⁺ and Mg, sign of the heat of mixing was estimated to be positive for all olivine, spinel and pyroxene. Relative concentration of Fe²⁺ in spinel in the pyroxene-spinel system is likely to cause some change in the chemical composition of modified spinel () or spinel () in the transition zone of the mantle. A considerable change is also expected in the transition pressure of to ( + ) and ( + ) to .Presented at the symposium Recent Advances in the Studies of Rocks and Minerals at High Pressures and Temperatures held in Montreal, 1972. Jointly sponsored by the International Mineralogical Association and the Commission on Experimental Petrology.  相似文献   

Step-like temperature fluctuations associated with inverted ramps in a stable surface layer   总被引：1，自引：0，他引：1  

Tokio Kikuchi  Osamu Chiba 《Boundary-Layer Meteorology》1985,31(1):51-63

Ensemble averages of temperature before and after step-like temperature fluctuations reveal the presence of inverted ramps in a stable surface layer. Normalized frequency of upward steps increases with increasing stability, whereas normalized magnitude of the temperature step decreases with stability and becomes constant at about R _i = 1. These results suggest that the significance of temperature steps increases as stability increases. In moderate stability, the temperature pattern shows a gradual decrease after an upward step, which can be called a time-inverted ramp. Descending air and large downward heat flux are observed in a time-inverted ramp, suggesting a contribution from an ordered motion in wind. On the other hand, the temperature steps are related to gravity waves in strong stability.  相似文献   

Seasonal cycle of manganese in seawater in Harima Sound     

Takayuki Shiozawa  Akira Hoshika  Osamu Takimura  Terumi Tanimoto 《Journal of Oceanography》1982,38(1):15-20

Vertical and horizontal distributions of manganese in Harima Sound (Harima Nada, Seto Inland Sea) were measured in August and December 1979. High concentrations of dissolved and particulate manganese were found in bottom waters in August, suggesting that the bottom enrichment is probably due to the diffusion of dissolved manganese out of the sediment. From measured distributions, we estimate the annual flux of manganese at the sediment-water interface to be more than 800 tons per year, if Harima Sound is a closed system for manganese.  相似文献