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41.
We studied the particle growth in a protoplanetary disk in a high-ionization environment and found that icy planet formation is inactive for a disk with an ionization rate 100 times higher than that of the present Solar System. In particular, in the case of M 10~(-7.4)M_☉yr~(-1), only rocky planet formation occurs. In such a case, all the solid materials in the disk drift inward, eventually reach the inner MRI front,and accumulate there. They form a dense, thin sub-disk of solid particles, which undergoes gravitational instability to form rocky planetesimals. The planetesimals rapidly grow into a planet through pebble accretion. Consequently, rocky planets tend to be much larger than planets formed through other regimes(tandem planet formation regime and dispersed planet formation regime), in which icy planet formation actively takes place. These rocky planets may evolve into hot Jupiters if they grow fast enough to the critical core mass of the runaway gas accretion before the dispersal of the disk gas, or they may evolve into super-Earths if the gas dispersed sufficiently early. 相似文献
42.
Yusuke Yachi Hiroshi Kitagawa Tak Kunihiro Eizo Nakamura 《Geostandards and Geoanalytical Research》2014,38(1):95-102
Software designed for analytical laboratories to guarantee traceability and accessibility of rocks with their geochemical properties has been developed. The software documents the sample origin, current sample location and the location of any sample subsets (e.g., thin sections, solutions, etc.), and archives all associated geochemical data sets. The software can be installed on a personal computer so is available for use in any laboratory and allows curation before and after publication. The software will be of use in integrating and sharing geological reference materials within and among institutes. In this article, the system design and implementation are detailed. All source codes for the software are available at http://dream.misasa.okayama-u.ac.jp/ . 相似文献
43.
44.
In integrated systems for accurate positioning, which consist of GNSS, INS, and other sensors, the GNSS positioning accuracy has a decisive influence on the performance of the entire system and thus is very important. However, GNSS usually exhibits poor positioning results in urban canyon environments due to pseudorange measurement errors caused by multipath creation, which leads to performance degradation of the entire positioning system. For this reason, in order to maintain the accuracy of an integrated positioning system, it is necessary to determine when the GNSS positioning is accurate and which satellites can have their pseudorange measured accurately without multipath errors. Thus, the objective of our work is to detect the multipath errors in the satellite signals and exclude these signals to improve the positioning accuracy of GNSS, especially in an urban canyon environment. One of the previous technologies for tackling this problem is RAIM, which checks the residual of the least square and identifies the suspicious satellites. However, it presumes a Gaussian measurement error that is more common in an open-sky environment than in the urban canyon environment. On the other hand, our proposed method can estimate the size of the pseudorange error directly from the information of altitude positioning error, which is available with an altitude map. This method can estimate even the size of non-Gaussian error due to multipath in the urban canyon environment. Then, the estimated pseudorange error is utilized to weight satellite signals and improve the positioning accuracy. The proposed method was tested with a low-cost GNSS receiver mounted on a test vehicle in a test drive in Nagoya, Japan, which is a typical urban canyon environment. The experimental result shows that the estimated pseudorange error is accurate enough to exclude erroneous satellites and improve the GNSS positioning accuracy. 相似文献
45.
A general constitutive equation for viscoelastic behaviour of rocks and minerals with fractional-order derivative is investigated. This constitutive law is derived based on differential geometry and thermodynamics of rheology, and the fractional order of derivative represents the degree of time delay. Analyzing some laboratory experimental data of high temperature deformation of rocks and minerals such as halite, marble and orthopyroxene, we propose how to determine the orders of fractional derivative for viscoelastic behaviours of rocks and minerals. The order is related to the exponents for the temporal scaling in the relaxation modulus and the stress power-law of strain rate, i.e., the non-Newtonian flow law, and considered as an indicator representing the macroscopic behaviour and microscopic dynamics of rocks. 相似文献
46.
Yoshinori Takano Jonathan James Tyler Hisaya Kojima Yusuke Yokoyama Yukiko Tanabe Takaharu Sato Nanako O. Ogawa Naohiko Ohkouchi Manabu Fukui 《Applied Geochemistry》2012
The paleolimnology of two lakes which were isolated as a result of the crustal uplift during the late Holocene along the Soya Coast, Lützow-Holm Bay, East Antarctica were studied. The focus was on temporal variations in the biogeochemical composition of sediment cores recovered from Lake Skallen at Skallen and Lake Oyako at Skarvsnes. Both sets of lake sediments record environmental changes associated with a transition from marine to lacustrine settings, as indicated by analyses of C and N contents, nitrogen isotopic compositions (δ15N), and major element concentrations. Changes in the dominant primary producers during the marine–lacustrine transition (marine diatom to cyanobacteria) at L. Skallen was clearly revealed by biogenic opal-A, diatom assemblages, and molecular signature from denaturing gradient gel electrophoresis (DGGE) with 16S ribosomal RNA (rRNA) gene analysis. Radiocarbon dating of acid-insoluble organic C suggested that the environmental transition from marine to fresh water occurred at 2940 ± 100 cal yr BP at L. Skallen and 1060 ± 90 cal yr BP at L. Oyako. Based on these data, a mean crustal uplift rate of 3.2 mm yr−1 is inferred for the history of marine–lacustrine transition via brackish conditions. The geological setting causing glacio-isostatic uplift was the primary factor in controlling the transition event in sedimentary and biological facies. 相似文献
47.
Sea ice thickness is highly spatially variable and can cause uneven ocean heat and salt flux on subgrid scales in climate models.Previous studies have demonstrated improvements in ocean mixing simulation using parameterization schemes that distribute brine rejection directly in the upper ocean mixed layer.In this study,idealized ocean model experiments were conducted to examine modeled ocean mixing errors as a function of the lead fraction in a climate model grid.When the lead is resolved by the grid,the added salt at the sea surface will sink to the base of the mixed layer and then spread horizontally.When averaged at a climate-model grid size,this vertical distribution of added salt is lead-fraction dependent.When the lead is unresolved,the model errors were systematic leading to greater surface salinity and deeper mixed-layer depth(MLD).An empirical function was developed to revise the added-salt-related parameter n from being fixed to lead-fraction dependent.Application of this new scheme in a climate model showed significant improvement in modeled wintertime salinity and MLD as compared to series of CTD data sets in 1997/1998 and 2006/2007.The results showed the most evident improvement in modeled MLD in the Arctic Basin,similar to that using a fixed n=5,as recommended by the previous Arctic regional model study,in which the parameter n obtained is close to 5 due to the small lead fraction in the Arctic Basin in winter. 相似文献
48.
Assessing flood disaster impacts in agriculture under climate change in the river basins of Southeast Asia 总被引:1,自引:0,他引:1
Shrestha Badri Bhakta Perera Edangodage Duminda Pradeep Kudo Shun Miyamoto Mamoru Yamazaki Yusuke Kuribayashi Daisuke Sawano Hisaya Sayama Takahiro Magome Jun Hasegawa Akira Ushiyama Tomoki Iwami Yoichi Tokunaga Yoshio 《Natural Hazards》2019,97(1):157-192
Natural Hazards - This study focused on flood damage assessment for future floods under the impact of climate change. Four river basins of Southeast Asia were selected for the study. They included... 相似文献
49.
We present a new united theory of planet formation,which includes magneto-rotational instability(MRl) and porous aggregation of solid particles in a consistent way.We show that the "tandem planet formation" regime is likely to result in solar system-like planetary systems.In the tandem planet formation regime,planetesimals form at two distinct sites:the outer and inner edges of the MRl suppressed region.The former is likely to be the source of the outer gas giants,and the latter is the source for the inner volatile-free rocky planets.Our study spans disks with a various range of accretion rates,and we find that tandem planet formation can occur for M = 10~(7.3)- 10~(-6.9)M_⊙yr~(-1).The rocky planets form between 0.4-2 AU,while the icy planets form between 6-30 All;no planets form in 2—6 AU region for any accretion rate.This is consistent with the gap in the solid component distribution in the solar system,which has only a relatively small Mars and a very small amount of material in the main asteroid belt from 2-6 AU.The tandem regime is consistent with the idea that the Earth was initially formed as a completely volatile-free planet.Water and other volatile elements came later through the accretion of icy material by occasional inward scattering from the outer regions.Reactions between reductive minerals,such as schreibersite(Fe-jP),and water are essential to supply energy and nutrients for primitive life on Earth. 相似文献
50.
Tsuyoshi Komiya Shinji Yamamoto Shogo Aoki Keiko Koshida Masanori Shimojo Yusuke Sawaki Kazumasa Aoki Shuhei Sakata Takaomi D. Yokoyama Kenshi Maki Akira Ishikawa Takafumi Hirata Kenneth D. Collerson 《地学前缘(英文版)》2017,8(2):355-385
The Archean continental crusts account for ca.20% of the present volume,but the thermal history of the Earths' mantle suggests much more continental crusts were formed in the early Archean.Because the Archean continental crust underwent severe metamorphism,it is important to avoid influence by the later thermal events.We carried out a comprehensive geochronological work of Cathodoluminescence(CL) observation and U-Pb dating of zircons from orthogneisses and supracrustal rocks over the Saglek Block to obtain their protolith ages.The zircons were classified into three domains of core,mantle and rims,and the cores were further classified into three groups of inherited,altered and zoned cores based on the zonation on the CL images.We estimated the protolith ages from Pb-Pb ages of the zoned-cores of zircons with low U contents.We made a detailed sketch of a small outcrop in St.John's Harbour South(SJHS) area,and classified the orthogneisses and mafic enclaves into seven generations based on the geologic occurrence.The first and second generations comprise mafic rocks and lack magmatic zircons.We conducted CL imaging and U-Pb dating of zircons from the third,sixth and seventh generation of the orthogneisses to estimate the protolith ages at 3902 L 25,3892 ± 33 and 3897 ± 33 Ma for each,supporting the presence of the over 3.9 Ca Iqaluk Gneiss.The geological occurrence that the mafic rocks occur as enclaves within the 3.9 Ga Iqaluk Gneiss indicates that they are the oldest supracrustal rocks in the world.Our geochronological and geological studies show the Uivak Gneiss is quite varied in lithology and age from 3.6 to 3.9 Ga,and tentatively classified into six groups based on their ages.The oldest Uivak Gneiss components including the Iqaluk Gneiss are present around the SJHS area,and the orthogneisses become young as it is away.The lines of evidence of overprinting of younger granitoid on older granitoid in small outcrops and geological-map scale as well as presence of inherited zircons even in the oldest suite suggests that crustal reworking played an important role on erasing the ancient crusts. 相似文献