Microscopic observation and contact stress analysis of granite under compression     

Y. S. Seo  G. C. Jeong  J. S. Kim  Y. Ichikawa 《Engineering Geology》2002,63(3-4):259-275

To study the damage process of microscale to macroscale in coarse-grained granite specimen under uniaxial compressive stress, we have observed micro-damage localization and propagation by using a newly developed experimental system that allows us to observe the damaging process continuously.

The results showed that pre-existing microcracks lead to macroscopic shear fracture through the damage development process. The mechanism of micro-damage initiation in a granite specimen under uniaxial compressive stress may be considered for two cases. One is that two grains such as quartz and feldspar contact each other in the same direction as the axial stress, and the other is that a biotite grain inclined to the axial stress direction is surrounded by feldspar grains. The homogenization theory was applied to verify numerically the micromechanics of stress-induced damage in the mineral contacts. Local stress distribution in the periodic-micro structure was also calculated by the homogenization theory. It is shown that this analysis, which takes into account the initial state of the specimen, is well adapted to the behavior of two grains for which microcracking is the fundamental mechanism of damage.  相似文献   

The skill of atmospheric linear inverse models in hindcasting the Madden–Julian Oscillation     

Nicholas R. Cavanaugh  Teddy Allen  Aneesh Subramanian  Brian Mapes  Hyodae Seo  Arthur J. Miller 《Climate Dynamics》2015,44(3-4):897-906

A suite of statistical atmosphere-only linear inverse models of varying complexity are used to hindcast recent MJO events from the Year of Tropical Convection and the Cooperative Indian Ocean Experiment on Intraseasonal Variability/Dynamics of the Madden–Julian Oscillation mission periods, as well as over the 2000–2009 time period. Skill exists for over two weeks, competitive with the skill of some numerical models in both bivariate correlation and root-mean-squared-error scores during both observational mission periods. Skill is higher during mature Madden–Julian Oscillation conditions, as opposed to during growth phases, suggesting that growth dynamics may be more complex or non-linear since they are not as well captured by a linear model. There is little prediction skill gained by including non-leading modes of variability.  相似文献   

A comparative study of toxicity identification using Daphnia magna and Tigriopus japonicus: implications of establishing effluent discharge limits in Korea     

Kang SW  Seo J  Han J  Lee JS  Jung J 《Marine pollution bulletin》2011,63(5-12):370-375

In Korea, the new permission criteria for industrial effluents based on Daphnia magna acute toxicity tests will be gradually implemented starting from 2011. Thus, in this study, toxicity assessment and identification using a marine species (Tigriopus japonicus) and the freshwater species (D. magna) was comparatively investigated. Effluent from an acid mine drainage treatment plant showed acute toxicity toward both organisms due to low pH, which was removed by neutralization of the effluent. Additionally, evaluation of the effluent of an electronics company revealed that Cu was attributable to the observed toxicity, and the effluent was more toxic toward T. japonicus than D. magna. Moreover, effluents from a metal plating factory were acutely toxic toward D. magna (6.50 TU), while they were not toxic against T. japonicus. Toxicity identification revealed that the high level of Cl- (12,841 mg L(-1)) was the cause of toxicity. Thus, the effluents had no effect on the marine species, T. japonicus. These findings suggest that a marine species rather than a freshwater species is more desirable for toxicity assessment of industrial effluent discharged into the saltwater, and thus should be considered in the legislation of toxicity-based discharge limits in Korea.  相似文献   

The solubility of copper in high-temperature magmatic vapors: A quest for the significance of various chloride and sulfide complexes   总被引：5，自引：0，他引：5  

Zoltán Zajacz  Jung Hun Seo  Philip M. Piccoli 《Geochimica et cosmochimica acta》2011,75(10):2811-2827

We conducted experiments to determine the effect of various chemical components (NaCl, KCl, HCl, FeCl₂, H₂S, SO₂) on the solubility of Cu in single phase aqueous vapors at 1000 °C and 150 MPa. The experiments were conducted in Au₉₇Cu₃ alloy capsules buffering Cu activities at 0.01. The volatile phase was sampled at run conditions by the entrapment of synthetic fluid inclusions in quartz. To test if the volatile phase had reached equilibrium before the isolation of the inclusions by fracture healing, we trapped two inclusion generations, one in an initially prefractured chip and another in a quartz chip that was fractured in situ during the experiments. The synthetic fluid inclusions were subsequently analyzed by laser ablation inductively coupled plasma mass spectrometry. In pure water, the apparent solubility of Cu is below the limits of detection of 6 μg/g, showing the low stability of hydroxy Cu complexes at our experimental conditions. The presence of alkali chlorides supports modest Cu solubility likely in the form of NaCuCl₂ and KCuCl₂ complexes. In the H₂O-H₂S (+SiO₂ and Au₉₇Cu₃) system at an fH₂S of 10.4 MPa the apparent solubility of Cu is lower by a factor of ∼5 than that in a S-free 0.5 m NaCl solution, showing that copper hydrosulfide complexes are only moderately stable at these conditions. Addition of 4.7 mol% of sulfur to the H₂O-NaCl system at an fO₂ of 0.4 log units below the Ni-NiO buffer, yielding dominantly H₂S species, results in only a moderate increase in apparent Cu solubility, which diminishes in the presence of HCl. The addition of KCl results in a strong increase of apparent Cu solubility in the presence of H₂S. The solubility of Cu increases with the fugacity of oxygen in both the H₂O-NaCl and the H₂O-S-NaCl system following an approximately fourth root relationship as expected based on the stoichiometry of the involved redox reactions. Replacement of NaCl by FeCl₂ exerted only a minor effect on the Cu solubility.Results of our experiments, combined with thermochemical data obtained by ab initio quantum chemical calculations, suggest dissolution of Cu dominantly as Na(/K)CuCl₂, Na(/K)Cu(HS)_2, H₂SCuHS, and Na(/K)ClCuHS, the relative abundance of which are dictated by the H₂S/total chloride and HCl/alkali chloride ratios.  相似文献   

An essay on the impact of climate change on US agriculture: weather fluctuations, climatic shifts, and adaptation strategies     

S. Niggol Seo 《Climatic change》2013,121(2):115-124

The impact of climate change on US agriculture has been debated for more than two decades, but the estimates ranged from no damage at the lower end to 80 % losses of grain yields at the higher end. This essay aims to help understand such divergent predictions by clarifying the concepts of weather and climate. First, the widely-read panel fixed effects models capture only the impacts of weather fluctuations but not of climate normals. Random weather fluctuations and climatic shifts are two different meteorological events and they have distinct implications on farming decisions. The former is perceived as random while the latter is perceived as non-random by the farmers. Using the historical corn yield data in the US, I explain the differences between the impact of random weather and that of climate change. Second, adaptation strategies to climatic changes and increased climate risks cannot be accounted for by the panel fixed effects models. Using the farm household data collected in sub-Saharan Africa and Latin America, I discuss quantitative significance of modeling adaptation strategies in the estimates of climate damage. Distinction between random weather fluctuations and climatic shifts is critical in modeling farming decisions, as they are fundamental to climate science, but is poorly understood by the impact researchers.  相似文献   

Surface albedo from the geostationary Communication,Ocean and Meteorological Satellite (COMS)/Meteorological Imager (MI) observation system     

Chang Suk Lee  Jong-Min Yeom  Kyeong-sang Lee  Minji Seo  Jinkyu Hong 《地理信息系统科学与遥感》2018,55(1):38-62

The surface albedo is an essential climate variable that is considered in many applications used for predicting climate and understanding the mechanisms of climate change. In this study, surface albedo was estimated using a bidirectional reflectance distribution function model based on Communication, Ocean and Meteorological Satellite/Meteorological Imager data. Geostationary orbiting satellite data are suitable for a level 2 product like albedo, which requires a synthetic process to estimate. The authors modified established methods to consider the geometry of the solar-surface-sensor of COMS/MI. Of note, the viewing zenith angle term was removed from the kernel integration used for estimating spectral albedo. Finally, the spectral (narrow) albedo was converted into the broadband albedo with shortwave length (approximately 0.3–2.5 μm). This study determined conversion coefficients using only one spectral albedo of visible channel. The estimated albedo had a relatively high correlation with Satellite Pour l’Observation de la Terre/Vegetation and low unweighted error values specific for land types or times. The validation results show that estimated albedo has a root mean square error of 0.0134 at Jeju flux site that indicates accuracy similar to that of other satellite-based products.  相似文献   

Flood risk assessment using regional regression analysis   总被引：2，自引：0，他引：2  

Young-Oh Kim  Seung Beom Seo  Ock-Jae Jang 《Natural Hazards》2012,63(2):1203-1217

This study aimed to create a flood risk map for ungauged regions, which have limited flood damage data and other relevant data. The fact that there is a shortage of data that are critical for the establishment of a flood assessment and mitigation plan is not surprising even in developed countries like South Korea. To address this problem, the regional regression concept in statistical hydrology was introduced to the flood risk assessment field in this study, and it was framed with a series of two regression functions: flood damage and regional coefficients. As the second regression function utilizes the local socioeconomic variables, the resulting flood risk map can reflect the spatial characteristics well. The proposed methodology was applied to create flood risk maps for the three metropolitan areas in South Korea. The comparison of the proposed methodology with the existing methods revealed that only the proposed methodology can produce a statistically meaningful flood risk map based on a recent major flood in 2001.  相似文献   

U–Pb SHRIMP zircon geochronology,petrogenesis, and tectonic setting of the Neoproterozoic Baekdong ultramafic rocks in the Hongseong Collision Belt,South Korea     

C.W. Oh  J. Seo  S.G. Choi  V.J. Rajesh  J.H. Lee 《Lithos》2012

The Hongseong area, located in the western Gyeonggi Massif, South Korea, can be correlated with the northern margin of the South China block (Yangtze Craton). This area experienced Neoproterozoic igneous activity related to subduction before the amalgamation of Rodinia. Several isolated, lenticular, and serpentinized ultramafic–mafic bodies occur in the Hongseong area. The Baekdong body, one of the largest ultramafic bodies, has been highly deformed and metamorphosed to eclogite- and granulite-facies. The petrogenesis and tectonic environment of the Baekdong rocks are assessed using the composition of unaltered cores of spinel and olivine grains, and show that these rocks represent the mantle section of a suprasubduction ophiolite. The rocks originated from oceanic lithosphere that formed during the transition from nascent back-arc to mature island arc, related to subduction roll-back. During the back-arc stage, Al-rich spinel harzburgite formed through melt–rock interaction caused by the intrusion of magma. This magma was produced in small amounts, by less than 10% of partial melting of the wedge mantle. Subsequently, during the mature island arc stage, Cr-rich spinel dunite formed through melt–rock interaction caused by the intrusion of relatively evolved magma that formed by 30–35% partial melting due to a high input of volatiles from the subducted slab and sediments. The Baekdong ultramafic rocks, together with the Bibong ultramafic rocks, indicate that a suprasubduction tectonic setting prevailed before the amalgamation of Rodinia (at 860–890 Ma) in the Hongseong area, which may be an extension of the northern margin of the Yangtze Craton.  相似文献   

GRACE's spatial aliasing error   总被引：2，自引：0，他引：2  

Ki-Weon Seo  Clark R. Wilson  Jianli Chen  Duane E. Waliser 《Geophysical Journal International》2008,172(1):41-48

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Comparative study on the fauna composition of intertidal invertebrates between natural and artificial substrata in the northeastern coast of Jeju Island     

Jae-Hoon Cha  Kwang-Bae Kim  Ji-Na Song  In-Soo Kim  Jeong-Bin Seo  Chul-Hwi Kwoun 《Ocean Science Journal》2013,48(4):319-328

This study was carried out to learn about differences in the sessile macrobenthic fauna communities between the artificial and natural habitats. There were some differences in terms of species composition and dominant species and community structure between two habitat types. The dominant species include Pollicipes mitella and Granuilittorina exigua in natural rocky intertidal zones; Monodonta labio confusa, Ligia exotica, Tetraclita japonica in the artificial rocky intertidal zones. Among all the species, L. exotica and T. japonica occurred only in the artificial rocky intertidal zone. The results of cluster analysis and nMDS analysis showed a distinct difference in community structure between artificial and natural rocky intertidal zones. The fauna in the natural rocky intertidal zones were similar to each other and the fauna in the artificial rocky intertidal zones were divided depending on the slope of the substratum. In the case of a sloping tetrapod, M. labio confusa and P. mitella were dominant, but at the vertical artificial seawall, Cellana nigrolineata, L. exotica T. japonica were dominant. The analysis of the species presented in natural and artificial rocky intertidal areas showed the exclusive presence of 10 species on natural rocks and 12 species on artificial rocks. The species in the natural rocky intertidal area included mobile gastropods and cnidarians (i.e. rock anemones), and the species in the artificial rocky intertidal area mostly included non-mobile attached animals. The artificial novel structure seems to contribute to increasing the heterogeneity of habitats for marine invertebrate species and an increase the species diversity in rocky coastal areas.  相似文献