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1.
Eiichiro Kokubo Keiko Yoshinaga & Junichiro Makino 《Monthly notices of the Royal Astronomical Society》1998,297(4):1067-1072
We describe a P(EC) n Hermite scheme for planetary N -body simulation. The fourth-order implicit Hermite scheme is a time-symmetric integrator that has no secular energy error for the integration of periodic orbits with time-symmetric time-steps. In general N -body problems, however, this advantage is of little practical significance, since it is difficult to achieve time-symmetry with individual variable time-steps. However, we can easily enjoy the benefit of the time-symmetric Hermite integrator in planetary N -body systems, where all bodies spend most of the time on nearly circular orbits. These orbits are integrated with almost constant time-steps even if we adopt the individual time-step scheme. The P(EC) n Hermite scheme and almost constant time-steps reduce the integration error greatly. For example, the energy error of the P(EC)2 Hermite scheme is two orders of magnitude smaller than that of the standard PEC Hermite scheme in the case of an N = 100, m = 1025 g planetesimal system with the rms eccentricity 〈 e 2 〉1/2 ≲0.03. 相似文献
2.
Microbial biomass response to different quantities and sources of organic matter in Brazilian coastal sediments 
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下载免费PDF全文 Cintia O. Quintana Paula C. de Moraes Marcos Y. Yoshinaga Stuart G. Wakeham Paulo Y. G. Sumida 《Marine Ecology》2015,36(3):766-779
This study investigates the benthic microbial responses to organic matter (OM) variations in quantity and sources in two shallow water bays (Fortaleza and Ubatuba Bays) on the SE coast of Brazil on six occasions during the year. The pelagic and benthic compartments of the bays were evaluated by: (i) nutrients and chlorophyll a (Chl a) in the water column; (ii) quantity and sources of OM in the sediment (Chl a, total organic carbon and total nitrogen and lipid biomarker composition); and (iii) microbial biomass in sediments as an indicator of active benthic response. Although there were changes in water‐column nutrients during the year, Chl a was fairly constant, suggesting a regular supply of microalgae‐derived OM to the sea bottom. Based on the composition of lipid biomarkers in sediments, OM sources were classified as mostly marine and with high contributions of labile (microalgae‐derived) OM. Labile OM composition varied from diatoms in the summer to phytoflagellates in the winter and tended to accumulate in areas protected by physical disturbances in one of the bays. Microbial biomass followed this trend and was 160% higher in protected than in exposed areas. This study suggests that the coupling between labile OM and benthic microbial biomass occurs primarily in protected areas, irrespective of the time of the year. Since meio‐ and macrofaunal assemblages depend upon secondary microbial production within the sediments, this coupling may have an important role for the benthic food‐web. 相似文献
3.
Design and Long-Term Monitoring of Tokyo International Airport Extension Project Constructed on Super-Soft Ground 总被引：1，自引：0，他引：1
K. Morohoshi K. Yoshinaga M. Miyata I. Sasaki H. Saitoh M. Tokoro N. Fukuda T. Fujii K. Yamada M. Ishikawa 《Geotechnical and Geological Engineering》2010,28(3):223-232
To meet the increasing demand for air transportation, Ministry of Land, Infrastructure and Transport had carried out the offshore
extension project at Tokyo International Airport (Haneda Airport). The airport should be constructed to be perfectly level,
but the ground conditions with very thick layers of super soft dredged soils and need for reclamation made the task very difficult.
Because of large amount of consolidation settlement, ground improvement by combined vertical drain method was applied to decrease
residual and differential settlement after opening of new airport. This paper is aimed to introduce the design concept and
method of ground improvement for this project. In addition the result of ground improvement is keeping satisfactory performance
for operating airport confirmed by long-term monitoring for airport facilities. 相似文献
4.
5.
Correlation of large displacement drained shear strength of landslide soils measured by direct shear and ring shear devices 总被引：2，自引：0，他引：2
Shriwantha Buddhi Vithana Shinya Nakamura Seiichi Gibo Anshun Yoshinaga Sho Kimura 《Landslides》2012,9(3):305-314
Based on a laboratory study of drained direct shear tests of remoulded, pre-cut and polished specimens and drained ring shear tests of uncut and remoulded specimens of slip surface materials of five landslide soils, significant correlations of the mobilized shear strength parameters, cohesion (c, c r) and internal friction angle (Φ, Φr), are proposed. The investigated soils consisted of the slip surface material belonging to tuffaceous clay, mudstone, loess and siltstone. Most of the previous studies on residual shear strength measured by reversal direct shear and ring shear devices have obtained significantly different results using the two devices, even when pre-cut and polished specimens were used in the direct shear device. In this study, the residual shear strength values of remoulded specimens measured by a ring shear device are shown to significantly correlate with the drained large displacement shear strength values of remoulded specimens, which were measured using pre-cut and polished specimens in a direct shear device. The correlation between the cohesion measured in the two shear devices is expressed by the linear relationship, $ {c_{\text{r}}} = 0.{7394}c - {6}.{6857} $ , while the correlation between the friction angle measured in the two devices is expressed by the linear relationship, $ {\Phi_{\text{r}}} = {1}.0{852}\Phi - {6}.0{247} $ . The proposed linear correlations for effective cohesion (c′) and effective friction angle (Φ′) have yielded significant coefficients of determination within an effective normal stress range of 30–150?kN/m2. 相似文献
6.
随着人们对地下矿产资源的过度开采,地下空间形成了较大区域的采空区。采空区出现后,其上覆岩层平衡条件被破坏,使得上覆岩层产生移动变形,直到破坏、塌落,导致地表建筑物变形、破坏,地表大面积下沉、凹陷,形成大面积的采空塌陷区。采空区的存在使矿山生产面临很大的安全问题。近年来,矿山采空区的危害越来越受到人们的重视,在采空区调查中,各种地球物理方法起到了重要的作用,国内外以往探测实践表明,较为常用的物探测量方法有:高密度电阻率法、瞬变电磁法、CSAMT法、浅层地震反射波法、放射性土壤氡气测量法等,但每种物探方法的应用均具有一定的条件,需要根据岩石物性特征、场地条件、探测深度、环境影响等因素选择合适的地球物理方法。地震反射波法具有抗干扰能力强、分辨率较高等优势,被较多应用于矿山采空区的调查中。该文以临沂市兰陵县某石膏矿采空区为例,采用浅层地震反射波法对该石膏矿采空区进行调查,通过对获得的地震剖面资料进行处理和解释,取得了较好的探测效果,其技术方法可为同类采空区的探测提供借鉴和指导。 相似文献
7.
Michael James Friedel Oderson Ant?nio de Souza Filho Fabio Iwashita Adalene Moreira Silva Sueli Yoshinaga 《Hydrogeology Journal》2012,20(6):1061-1080
It is not possible, using numerical methods, to model groundwater flow and transport in the fractured crystalline rock of northeastern Brazil. As an alternative, the usefulness of self-organizing map (SOM), k-means clustering, and Davies-Bouldin techniques to conceptualize the hydrogeology was evaluated. Also estimated was the well yield and groundwater quality across the Juá region. This process relies on relations in the underlying multivariate density function associated with a sparse local set of hydrogeologic (electrical conductivity, geology, temperature, and well yield) and a complete regional set of airborne geophysical (electromagnetic, magnetic, and radiometric) and satellite spectrometric measurements. Resampling of the regional well yield and electrical conductivity estimates provides sufficient resolution to construct variograms for stochastic modeling of the hydrogeologic variables. The combination of these stochastic maps provides a way to identify potential drilling targets for future groundwater development. The data-driven estimation approach, when applied to available airborne electromagnetic and water-well hydrogeologic measurements, provides a low-cost alternative to numerical groundwater flow modeling. In addition to fractured rock environments, the alternative modeling framework can provide spatial parameter estimates and associated variograms for constraints to improve the traditional calibration of equivalent groundwater-porous-media models. 相似文献
8.
Radon concentrations in soil gas,considering radioactive equilibrium conditions with application to estimating fault-zone geometry 总被引：1，自引：0，他引：1
A calculation method for determining the amount of Rn isotopes and daughter products at the start of measurement (CRAS) is
proposed as a more accurate means of estimating the initial Rn concentration in soil gas. The CRAS utilizes the decay law
between 222Rn and 220Rn isotopes and the daughter products 218Po and 216Po, and is applicable to α-scintillation counter measurements. As Rn is both inert and chemically stable, it is useful for
fault investigation based on the soil gas geochemistry. However, the total number of α particles emitted by the decay of Rn
has generally been considered to be proportional to the initial Rn concentration, without considering the gas condition with
respect to radioactive equilibrium. The CRAS method is shown to be effective to derive Rn concentration for soil gases under
both nonequilibrium conditions, in which the total number of decays increases with time, and equilibrium conditions, which
are typical of normal soil under low gas flux. The CRAS method in conjunction with finite difference method simulation is
applied to the analysis of two active fault areas in Japan, and it is demonstrated that this combination could detect the
sharp rises in 222Rn concentrations associated with faults. The method also allows the determination of fault geometry near the surface based
on the asymmetry variation of the Rn concentration distribution when coupled with a numerical simulation of 222Rn transport. The results for the new method as applied to the two case studies are consistent with the data collected from
the geological survey. It implies that the CRAS method is suitable for investigating the fault system and interstitial gas
mobility through fractures. The present analyses have also demonstrated that high Rn concentrations require the recent and
repeated accumulation of 222Rn parents (230Th and 226Ra) in fault gouges through deep gas release during fault movement. 相似文献
9.
Organic matter quality, expressed as the proportion of chlorophyll a (Chl a) to degraded organic material (i.e. phaeopigments), is known to influence the structure of benthic associations and plays an important role in the functioning of the ecosystem. This study investigates the vertical distribution of microbial biomass, meiofauna and macrofauna with respect to organic matter variation in Ubatuba, Brazil, a southeastern, subtropical coastal area. On three occasions, samples were collected in exposed and sheltered stations, at high and low hydrodynamic conditions. We hypothesize that benthic assemblages will have high meio‐ and macrofaunal densities and high microbial biomass at the sediment surface at the sheltered site, and lower and vertically homogeneous microbial biomass and densities of meio‐ and macrofauna are expected at the exposed site. The accumulation of fresh organic matter at the sediment surface was observed at both stations over the three sampling dates, which contributed to the higher densities of meiofauna in the first layers of the sediment column. Macrofauna followed the same trend only at the exposed station, but changes in the number of species, biodiversity and feeding groups were registered for both stations. Microbial biomass increased at the sheltered station over the three sampling dates, whereas at the exposed station, microbial biomass was nearly constant. Physical exposure did not influence organic matter loading at the sites and therefore did not affect overall structure of benthic assemblages, which negates our original hypothesis. Most of the benthic system components reacted to organic matter quality and quantity, but relationships between different‐sized organisms (i.e. competition and/or predation) may explain the unchanged microbial profiles at the exposed site and homogeneous vertical distribution of macrofauna at the sheltered site. In conclusion, the high quality of organic matter was a crucial factor in sustaining and regulating the benthic system, but coupled results showed that interactions between micro‐, meio‐ and macrofauna can be highly complex. 相似文献
10.
LI Guochen FENG Chengyou WANG Ruijiang LI Hongmao ZHOU Anshun MA Shengchao LIU Jiannan XIAO Ye 《地质学报》2012,86(1)
地处东、西昆仑与阿尔金构造带结合处的白干湖是近年在我国西北地区勘查发现的一处具超大型远景规模的钨锡矿田,包括柯可卡尔德、白干湖、巴什尔希和阿瓦尔四个矿床.其中,柯可卡尔德钨锡矿勘查程度最高、规模最大,野外调查发现其含矿石英脉体有沿走向扭动、雁列式排列、产状低缓等特征,热液活动则可明显分为成矿前、成矿期和成矿后三期作用.该矿床流体包裹体主要有汽液两相、含子盐汽液三相、单一液相(包括纯水和纯CO2型)、含CO2汽液三相、同时含CO2和子盐汽液四相等5种类型,成矿前石英以前两种包裹体为主,亦有少量含CO2汽液三相型;成矿期可分为早、晚两个阶段,早阶段是钨锡的主成矿阶段,包含五种类型包裹体,晚阶段表现为弱的硫化物矿化,主要为汽液两相型;成矿后石英包裹体主要为汽液两相型.显微测温与激光拉曼探针分析表明成矿流体主要成分为H2O和CO2,气相含少量CH4和N2;氢、氧同位素研究结果显示三期流体分别主要为变质热液、岩浆热液和大气降水.该矿床系中高温、中低盐度的岩浆热液矿床,流体经历了不混溶作用和混合作用,这可能是促使矿质沉淀的主要因素. 相似文献