Two extraterrestrial dust horizons found in the Dome Fuji ice core,East Antarctica     

Keiji Misawa  Mika Kohno  Takayuki Tomiyama  Takaaki Noguchi  Tomoki Nakamura  Keisuke Nagao  Takashi Mikouchi  Kunihiko Nishiizumi 《Earth and Planetary Science Letters》2010,289(1-2):287-297

Two silicate-rich dust layers were found in the Dome Fuji ice core in East Antarctica, at Marine Isotope Stages 12 and 13. Morphologies, textures, and chemical compositions of constituent particles reveal that they are high-temperature melting products and are of extraterrestrial origin. Because similar layers were found ～ 2000 km east of Dome Fuji, at EPICA (European Project for Ice Coring in Antarctica)-Dome C, particles must have rained down over a wide area 434 and 481 ka. The strewn fields occurred over an area of at least 3 × 10⁶ km². Chemical compositions of constituent phases and oxygen isotopic composition of olivines suggest that the upper dust layer was produced by a high-temperature interaction between silicate-rich melt and water vapor due to an impact explosion or an aerial burst of a chondritic meteoroid on the inland East Antarctic ice sheet. An estimated total mass of the impactor, on the basis of particle flux and distribution area, is at least 3 × 10⁹ kg. A possible parent material of the lower dust layer is a fragment of friable primitive asteroid or comet. A hypervelocity impact of asteroidal/cometary material on the upper atmosphere and an explosion might have produced aggregates of sub-μm to μm-sized spherules. Total mass of the parent material of the lower layer must exceed 1 × 10⁹ kg. The two extraterrestrial horizons, each a few millimeters in thickness, represent regional or global meteoritic events not identified previously in the Southern Hemisphere.  相似文献   

Effects of Earth's curvature and radial heterogeneity in dislocation studies:Case studies of the 2008 Wenchuan earthquake and the 2004 Sumatra earthquake          下载免费PDF全文

Guangyu Fu  Wenke Sun  Yoichi Fukuda  Shanghua Gao  Takashi Hasegawa 《地震科学（英文版）》2010,23(4):301-308

Recently,effects of Earth's curvature and radial heterogeneity on coseismic deformations are often investigated based on the 2004 Sumatra earthquake.However,such effects are strongly related to earthquake types.As a low dip angle event,the 2004 Sumatra earthquake is not a good seismic case for such a topic since the effects for moderate dip angle events are much bigger.In this study,the half-space and spherical dislocation theories are used,respectively,to calculate coseismic displacements caused by the 2008 Wenchuan earthquake and the 2004 Sumatra earthquake.Effects of Earth's curvature and stratification are investigated through the discrepancies of results calculated using the two dislocation theories.Results show that the effects of Earth's curvature and stratification for the 2008 Wenchuan earthquake are much larger than those for the 2004 Sumatra earthquake.Ignoring the effects will cause errors up to 100%-200% in far field displacements for a moderate dip angle event like the 2008 Wenchuan earthquake.Such great effects are much bigger than those conclusions of previous studies.Besides,comparison with observations verifies that spherical dislocation theories yield better results than half-space ones in far fields.  相似文献   

On the use of JMA intensity in earthquake early warning systems     

Vladimir Sokolov  Takashi Furumura  Friedemann Wenzel 《Bulletin of Earthquake Engineering》2010,8(4):767-786

The estimation of strength of shaking at a site from the initial P-wave portion of ground motion is the key problems for shortening the alert time of the earthquake Early Warning (EEW). The most of the techniques proposed for the purpose utilize (a) ground motion models based on the estimated magnitude and hypocentral distance, or (b) the interim proxies, such as initial vertical displacement P _d . We suggest the instrumental Japan Meteorological Agency (JMA) intensity (JMA_I) as a characteristic for fast estimation of damage potential in the EEW systems. We investigated the scaling relations between JMA_I measured using the whole earthquake recordings (overall intensity) and using particular time intervals of various duration (2.0–8.0 s) starting from the P-wave arrival (preliminary intensity). The dataset included 3,660 records (K-NET and the KiK-net networks) from 55 events (M _W 4.1–7.4) occurred in 1999–2008 in Japan. We showed that the time interval of 4–5 s from the P-wave arrival can be used for reliable estimations of the overall intensity with the average standard error of about 0.5 JMA units. The uncertainty in the prediction may be reduced by consideration of local site conditions or by development of the station-specific models.  相似文献   

Experiment study on RC frame retrofitted by the external structure     

Chunyang Liu  Junji Shi  Kuramoto Hiroshi  Takashi Taguchi  Takashi Kamiya 《地震工程与工程振动(英文版)》2016,15(3):563-574

A new retrofitting method is proposed herein for reinforced concrete (RC) structures through attachment of an external structure. The external structure consists of a fiber concrete encased steel frame, connection slab and transverse beams. The external structure is connected to the existing structure through a connection slab and transverse beams. Pseudostatic experiments were carried out on one unretrofitted specimen and three retrofitted frame specimens. The characteristics, including failure mode, crack pattern, hysteresis loops behavior, relationship of strain and displacement of the concrete slab, are demonstrated. The results show that the load carrying capacity is obviously increased, and the extension length of the slab and the number of columns within the external frame are important influence factors on the working performance of the existing structure. In addition, the displacement difference between the existing structure and the outer structure was caused mainly by three factors: shear deformation of the slab, extraction of transverse beams, and drift of the conjunction part between the slab and the existing frame. Furthermore, the total deformation determined by the first two factors accounted for approximately 80% of the damage, therefore these factors should be carefully considered in engineering practice to enhance the effects of this new retrofitting method.  相似文献   

Configuring high frequency radar observations in the Southern Chukchi Sea   总被引：1，自引：1，他引：0  

Gleb Panteleev  Max Yaremchuk  Oceana Francis  Takashi Kikuchi 《Polar Science》2013,7(2):72-81

In recent years, monitoring offshore surface circulation in the Arctic Ocean with high frequency radars has become an issue of increasing practical importance. In this study, radar positions are optimized by minimizing the reconstruction errors of the surface currents in the Southeastern Chukchi Sea. By means of an adjoint sensitivity technique it is shown that in the case of a pair of radars, their optimal (i.e. most favorable) location is at Kivalina, a settlement near the strongest outflow of the Alaskan Coastal Current from the monitored domain. The least favorable location is at Shishmaref, a settlement near relatively weak inflow into the region as observed from the coast. However, if two pairs of radars are available, the best locations are Kivalina and Shishmaref. The results are verified using observational system simulation experiments (OSSEs) performed in the framework of a 4-dimensional variational assimilation of simulated radar observations into a numerical model. It is shown that correct specification of the first guess solution is of primary importance for obtaining realistic results from both adjoint sensitivity analysis and OSSEs. This emphasizes the necessity of obtaining accurate high resolution climatologies for future ice-free offshore regions in the Arctic.  相似文献   

Reflection on the development of the tool kits of Bertin’s methods     

Takashi Morita 《制图学和地理信息科学》2013,40(2):140-151

ABSTRACT

Bertin’s first book, Semiology of Graphics, was published in 1967. His second book, Graphics and Graphic Information Processing, was subsequently published in 1977. The word “processing” in the title of the second book is interesting because in those days there were no personal computers with an interactive display system. But in Bertin’s laboratory there were many kinds of tool kits – basically manually developed thematic maps and data analysis. Bertin’s methods were concerned with making a thematic map and data visualization. Maps, and more generally graphics, were represented by sets of cartographic symbols. Thus, they are abstractions that demand both theoretical and technical literacy to represent and understand them. If the representation is systematic, a sort of tool kit might be necessary, because the representation demands consistency based on the theory. Otherwise a cartographer faces the risk of an unstable and unintelligible representation. In this paper, we discuss the discrimination between tool kits intended either for an automated system or a process assisting system. The latter process might be useful and necessary to develop a graphic way of thinking. This investigation refers to Bertin’s books, materials conserved at the National Archives in Paris, and other related software developed later.

Abbreviation: EHESS: Ecole des Hautes Etudes en Sciences Sociales inherited Ecole Pratique des Hautes Etudes since 1975  相似文献   

Practical evaluation of carbon sources of forest soils in Slovenia from stable and radio-carbon isotope measurements     

Ryoko Fujiyoshi  Hikaru Amano  Yousuke Sakuta  Kazumasa Okamoto  Takashi Sumiyoshi  Ivan Kobal  Janja Vaupoti? 《Environmental Earth Sciences》2012,67(1):133-140

Carbon sources were estimated by measuring carbon isotope ratios (??¹³C and ??¹⁴C) with accelerator mass spectrometry (AMS) in forest soils of different lithology. Six locations were selected in temperate deciduous and coniferous stands in Slovenia (?irovski vrh, Idrija, Ko?evski Rog, Pohorje, Gori?nica, and Rakitna), where carbonate rocks consisting of limestone and dolomite are abundant as underlying bedrock. Carbon isotope fractionation would not have occurred in two carbonaceous soils, since the values of both ??¹³C and ??¹⁴C changed consistently in these soils after thermal (550°C, 2?h) or chemical (1?M HCl, 24?h) treatments. Organic components were found to be predominant carbon sources (70?C100%) in the uppermost portions (0?C2?cm in depth). In deeper portions at a depth of about 30?C35?cm, soil carbon may be derived completely from underlying carbonate minerals in Idria, western part of Slovenia. The Combination of heat and chemical treatments with AMS provides practical information on soil carbon sources in carbonaceous soils.  相似文献   

Detection and isolation of p-nitrophenol-lowering bacteria from intestine of marine fishes caught in Japanese waters     

Kuda T  Kyoi D  Takahashi H  Obama K  Kimura B 《Marine pollution bulletin》2011,62(8):1622-1627

To determine the existence of p-nitrophenol (PNP)-lowering bacteria in intestine of Japanese coastal fish, the gastro-intestinal contents were incubated in Brain Heart Infusion (BHI) broth and minimal medium (MM) broths containing 1 mmol/L PNP at 30 °C for 7 days. Among 26 samples of 19 fish species, 17 samples showed a decrease in PNP of 0.5-0.8 mmol/L in BHI broth, but no decrease was shown in MM broth. Eighteen PNP-lowering bacterial strains were isolated from four fishes. All of the strains were identified as Lactococcus lactis subsp. lactis. Three L. lactis strains JS1-3 isolated from Japanese seabass Lateolabrax japonicus showed the highest PNP-lowering activity (0.44 mmol/L). Optimum temperature and pH for the growth and PNP decreasing corresponded with the marine environment. These results suggested that marine fishes have PNP decreasing bacteria in their intestine. These bacteria might protect host fish from toxicities of PNP and PNP related compounds.  相似文献   

Numerical analysis on seismic response of Shinkansen bridge-train interaction system under moderate earthquakes     

Mitsuo Kawatani  Toshiro Hayashikawa  Takashi Matsumoto 《地震工程与工程振动(英文版)》2011,10(1):85-97

This study is intended to evaluate the influence of dynamic bridge-train interaction (BTI) on the seismic response of the Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic BTI in seismic design.  相似文献   

Performance of dry-separation processes in the recovery of cenospheres from fly ash and their implementation in a recovery unit     

H.T.B.M. Petrus  Tsuyoshi Hirajima  Yuji Oosako  Moriyasu Nonaka  Keiko Sasaki  Takashi Ando 《International Journal of Mineral Processing》2011,98(1-2):15-23

Cenospheres recovery is one of the coal fly ash beneficiations, providing economic as well as environmental benefits. Current techniques, such as lagoon or other wet-separation processes, consume large amounts of water and add to water pollution due to leaching of toxic materials from fly ash. The other possible disadvantage is the need for a wide operational area, which is unsuitable for densely populated countries. As wet-separation processes have some disadvantages, an improved and/or sustainable alternative recovery technique is required. An air classifier is one of the alternative techniques. In this study, two types of air classifiers, namely a closed-type pneumatic separator and a micron separator, have been investigated. In terms of separation efficiency, it was found that the micron separator has the potential to be applied in cenospheres recovery from coal fly ash, giving a Newton's efficiency of 0.44, as compared to a value of about 0.26 for the closed-type pneumatic separator. The cenospheres recoveries of both pieces of equipment at their optimum Newton's efficiencies were similar at over 60 wt.%. The separation performance was further assessed from the particle distributions of the overflow and underflow products obtained from both pieces of equipment, as well as from SEM images. It was found that the lower Newton's efficiency of the closed-type pneumatic separator was due to the re-concentration of fine particles in the underflow product at air-flow rates higher than 2.2 m/s (the underflow product yield was about 55 wt.%).In order to further confirm the applicability of this technique, the micron separator, which had provided higher separation efficiency and cenospheres recovery, was deployed in a cenospheres recovery unit prior to the use of a wet-separation process (float and sink tank). About 80% of the cenospheres was recovered, with an 87.8% reduction in the total mass of fly ash to be separated in the float and sink tank. Consequently, much less water was needed for the process of cenospheres recovery. Moreover, it was also confirmed that the micron separator could yield higher quality fly ashes, that is, fly ash types I and II, from lower feed quality of fly ash type IV, which is the lowest category in commercial classification of fly ash according to JIS A6201.  相似文献