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91.
An analysis has been made of the narrow intensity spikes occurring in two cosmic gammaray bursts which were observed with a fast time resolution germanium spectrometer on board the low altitude polar orbiting satellite 1972-076B (Imhofet al., 1974a, 1975; Nakanoet al., 1974a). The bursts on 18 December, 1972 and 21 July, 1973, were also recorded on the Vela satellite system. The durations of three spikes were observed to be 0.06 s with the limits being 0.03 to 0.10 s. Four other narrow spikes were measured to have time width limits between 0.001 and 0.10 s. An additional eight spikes had widths less than 0.9 s. During the spikes, the gamma-ray intensities increased by factors of 2 to 10, with a median value of 3. These and other characteristics of the fast time structure are presented.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
92.
93.
Short-Range Prediction Experiments with Operational Data Assimilation System for the Kuroshio South of Japan 总被引:3,自引:3,他引:3
Masafumi Kamachi Tsurane Kuragano Satoshi Sugimoto Kumi Yoshita Toshiyuki Sakurai Toshiya Nakano Norihisa Usui Francesco Uboldi 《Journal of Oceanography》2004,60(2):269-282
The short-range (one month) variability of the Kuroshio path was predicted in 84 experiments (90-day predictions) using a
model in an operational data assimilation system based on data from 1993 to 1999. The predictions started from an initial
condition or members of a set of initial conditions, obtained in a reanalysis experiment. The predictions represent the transition
from straight to meander of the Kuroshio path, and the results have been analyzed according to previously proposed mechanisms
of the transition with eddy propagation and interaction acting as a trigger of the meander and self-sustained oscillation.
The reanalysis shows that the meander evolves due to eddy activity. Simulation (no assimilation) shows no meander state, even
with the same atmospheric forcing as the prediction. It is suggested therefore that the initial condition contains information
on the meander and the system can represent the evolution. Mean (standard deviation) values of the axis error for all 84 cases
are 13, 17, and 20 (10, 10, and 12) km, in 138.5°E, in the 30-, 60-, and 90-day predictions respectively. The observed mean
deviation from seasonal variation is 30 km. The predictive limit of the system is thus about 80 days. The time scale of the
limit depends on which stage in the transition is adopted as the initial condition. The gradual decrease of the amplitude
in a stage from meander to straight paths is also predicted. The predictive limit is about 20 days, which is shorter than
the prediction of the opposite transition.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
94.
Solar wind speeds (SWSs) estimated by interplanetary scintillation (IPS) observations during Carrington rotation 1753 are projected onto the so-called source-surface of 2.5 solar radii along magnetic field lines in interplanetary space. The following two working hypotheses are examined from different points of view: (1) The SWS is a weighted mean along the line of sight to a radio source; the weight for the SWS depends on the distance from theP-point, the closest approach to the Sun on the line of sight. (2) The weighting function has a very sharp peak at theP-point, so that the SWS shows a real solar wind speed at theP-point. In both the two cases, the SWSs projected onto the source surface are further projected onto the photosphere along magnetic field lines in the corona. Footpoints of these field lines are inferred as photospheric source regions of the solar wind. The intensity of the Hei (1083 nm) absorption line (HEI) in the chromosphere corresponding to these photospheric sources is interpolated from observational data. The weighted mean of the HEI is calculated in case 1. The HEI corresponding to theP-point is used in case 2. The SWS is compared with the HEI in both the two cases. It is found that the correlation between the SWS and the HEI is better in case 2 than in case 1. It is further inferred by correlation analysis between the SWS and the HEI that the solar wind is accelerated within 27 solar radii on average. Although the data examined in this paper were limited to just one solar rotation, these results suggest that the SWS estimated by the IPS technique corresponds to the solar wind speed near theP-point and the weighting function along the line of sight may have a very sharp peak near theP-point. 相似文献
95.
Ayako Shinozaki Hiroyuki Kagi Hisako Hirai Hiroaki Ohfuji Taku Okada Satoshi Nakano Takehiko Yagi 《Physics and Chemistry of Minerals》2016,43(4):277-285
Stability and phase relations of coexisting enstatite and H2 fluid were investigated in the pressure and temperature regions of 3.1–13.9 GPa and 1500–2000 K using laser-heated diamond-anvil cells. XRD measurements showed decomposition of enstatite upon heating to form forsterite, periclase, and coesite/stishovite. In the recovered samples, SiO2 grains were found at the margin of the heating hot spot, suggesting that the SiO2 component dissolved in the H2 fluid during heating, then precipitated when its solubility decreased with decreasing temperature. Raman and infrared spectra of the coexisting fluid phase revealed that SiH4 and H2O molecules formed through the reaction between dissolved SiO2 and H2. In contrast, forsterite and periclase crystals were found within the hot spot, which were assumed to have replaced the initial orthoenstatite crystals without dissolution. Preferential dissolution of SiO2 components of enstatite in H2 fluid, as well as that observed in the forsterite H2 system and the quartz H2 system, implies that H2-rich fluid enhances Mg/Si fractionation between the fluid and solid phases of mantle minerals. 相似文献
96.
Stable isotope exchange processes between solid and liquid phases of a natural melting snowpack are investigated in detail by separating the liquid water from snow grains at different depths of the snowpack and collecting the bottom discharge using a lysimeter. In the melting–freezing mass exchange process between the two phases, the theoretical slope of the δD? δ18O line for newly refrozen ice is calculated to be nearly that of pore water. However, based on observations of the isotopic evolution and snow grain coarsening of the snowpack, it is demonstrated that the slope of the δD? δ18O line for newly refrozen ice is equal to that of the original ice. This is proved to be due to preferential water flow in the snowpack, which leads to relatively more deuterium and less oxygen‐18 in the mobile water than the immobile water because of the kinetic effect. Higher mass exchange rate in the mobile water region results in excess deuterium in the bulk refrozen ice, compared with the fractionation of uniform fractionation factors and exchange rate. This effect, which is termed the ‘preferential exchange rate effect of isotopic fractionation’, is shown to be larger in the lower part than the upper part of the snowpack. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
97.
Akiko Nakano Kiyoshi Kurosawa Uddin Md. Shamim Masakazu Tani 《Environmental Earth Sciences》2014,72(9):3269-3280
Arsenic contamination of well water is a serious issue in the Nawalparasi District of the Terai region in Nepal. A local investigation was carried out on 137 tube wells in 24 communities of the district in December 2011. The investigation revealed that the average arsenic concentration in the tube wells was 350 μg/L, and that nearly 98 % of the wells exceeded the WHO guideline arsenic level limit of 10 μg/L. Highly contaminated well water, with more than 400 μg/L of arsenic, was found within the limited depth ranges of 18–22 and 50–80 m. High arsenic levels exceeding 500 μg/L were detected in shallower wells at Patkhauli, Mahuawa, Thulokunwar, and Goini located between 27.517° and 27.543°N and between 83.648° and 83.748°E. Boring sampling at five communities of Kashiya, Goini, Sanokunwar, Thulokunwar, and Mahuawa revealed two aquifers located at the two depths around 14–22 and 41–50 m in each community. Dark gray or black-colored peaty clay layers rich in organic matter were distributed at depths of 18–21 m beside the upper aquifers with high arsenic concentration in each community. Positive correlations were shown between iron and arsenic in the sediments from the five communities. It can be inferred that these results were caused by dissolution of iron-oxyhydroxide molecules with arsenic from solid phases. Microbial metabolisms have a great potential to induce the dissolution and release arsenic attached on the solid phases into aqueous phases depending on the level of redox potential and pH. 相似文献
98.
Masaya Masayoshi Saito Kiyotaka Tanikawa 《Celestial Mechanics and Dynamical Astronomy》2007,98(2):95-120
The dynamical structure of phase space of gravitational Newtonian three bodies which lie on a line (rectilinear three-body
system) is studied. We take an initial value plane and classify the points on the plane according to the fate of the orbits
starting from the points, using symbol sequences. The structure appearing on the initial value plane with this classification
was well studied for the equal-mass case (Tanikawa and Mikkola 2000, Chaos 10, 649–657). In this paper, we follow and clarify the changes of this structure with the mass ratio of three particles. 相似文献
99.
Masayoshi Oka 《Transactions in GIS》2011,15(1):109-123
This article demonstrates a way to model the urban microclimate using a combination of statistical analysis and a geographic information system (GIS). Field measurements of ambient temperature and relative humidity were collected in various urban settings at ground level over two surface materials and at two different times of the day. A panel autoregressive (PAR) model was created to conduct a regression analysis capable of accounting for the spatial autocorrelation. With the PAR analyses, selected urban street characteristics showed varying effects over the different surface materials and at different times of the day. The overall influences were consistent with previous findings. PAR models were then applied in GIS to create thermal prediction maps for the study area to determine the hot and cool spots. Since GIS is the most commonly used technology among a wide range of researchers and professionals, this article provides a means to improve the synthesis, integration, and sharing of information to understand the relationship between the heat‐vulnerable population and heat stress within the urban environment. This methodology will be useful in the effort to reduce the heat‐related morbidity and mortality, which are expected to increase with projected global warming. 相似文献
100.
The formation factor, the dimensionless electric resistivity of porous rock/sediment saturated with conductive fluid, is an important quantity in geophysical exploration for petroleum reservoirs and groundwater aquifers. The renormalization technique is a promising approximation method for the quick estimation of the formation factors from large three-dimensional images of porous geo-materials obtained by X-ray microtomography. In the present study, we applied the renormalization technique to various pore-scale image sets of real geo-materials (sandstones, pumice, lava, and sandy sediments). The purpose is to explore the factors controlling the estimation accuracy of the formation factor. The results revealed that the accuracy increases with increasing (i) porosity, (ii) degree of the pore elongation along the direction of the applied electric field, and (iii) size of the initial subsystem with which the renormalization step starts and with decreasing (iv) pore or grain size. Most importantly, a high degree of elongation of the pore structure along the applied field ensures good accuracy even if the porosity is low, the initial subsystem is small, and the pore or grain size is large. 相似文献