Optical dating of hydromagmatic volcanoes on the southwestern coast of Jeju Island, Korea     

C.S. Cheong  J.H. Choi  Y.K. Sohn  J.C. Kim  G.Y. Jeong 《Quaternary Geochronology》2007,2(1-4):266-271

Jeju Island, the largest Quaternary volcanic island in Korea, has formed mostly since the early Pleistocene, but its latest chronology of volcanism and sedimentation is still poorly constrained. Here we report optically stimulated luminescence (OSL) ages for two hydromagmatic volcanoes on the southwestern coast of Jeju Island, i.e., the Songaksan and Suwolbong tuff rings. The basaltic tuffs of these volcanoes contain abundant quartz sands from underlying marine sedimentary sequences. Two samples collected from the middle part of the Songaksan Tuff yielded highly reproducible quartz single-aliquot regenerative-dose (SAR) OSL ages of 7.0±0.3 ka, providing the first direct age estimate of Holocene volcanism in Jeju Island. The quartz OSL age estimate of 5.1±0.3 ka for the younger reworked basaltic tuff (the Hamori Formation) is comparable with previous radiocarbon and U-series disequilibrium dating of fossil mollusk shells. Two samples from the Suwolbong Tuff show quartz OSL age estimates of 18.3±0.7 and 18.6±0.9 ka, which are identical within error ranges and younger than the quartz OSL age estimate of 23.2±1.0 ka for the underlying Gosan Formation. This study confirms that volcanism and attendant sedimentation were active in Jeju Island until very recently.  相似文献   

Maps as Knowledge Aggregators: from Renaissance Italy Fra Mauro to Web Search Engines     

Andrea Nanetti  Angelo Cattaneo  Siew Ann Cheong  Chin-Yew Lin 《The Cartographic journal》2013,50(2):159-167

Abstract

For many years geological students have been graduating from universities with little knowledge of how to use the cartographic language of line, letter, symbol and tone by which the distribution and spatial arrangement of earth science data can be best expressed. The author discusses the development of the teaching of geological cartography in the Department of Earth Sciences at the University of Leeds. Details of this innovation are set against the background of data obtained from a recent questionnaire on the practice of cartography as a discipline in departments of geology in British universities.  相似文献   

Groundwater nitrate contamination and risk assessment in an agricultural area,South Korea   总被引：2，自引：1，他引：1  

Jae-Yeol Cheong  Se-Yeong Hamm  Jeong-Hwan Lee  Kwang-Sik Lee  Nam-Chil Woo 《Environmental Earth Sciences》2012,66(4):1127-1136

The nitrate of groundwater in the Gimpo agricultural area, South Korea, was characterized by means of nitrate concentration, nitrogen-isotope analysis, and the risk assessment of nitrogen. The groundwaters belonging to Ca–(Cl + NO₃) and Na–(Cl + NO₃) types displayed a higher average NO₃ ⁻ concentration (79.4 mg/L), exceeding the Korean drinking water standard (<44.3 mg/L NO₃ ⁻). The relationship between δ¹⁸O–NO₃ ⁻ values and δ¹⁵N–NO₃ ⁻ values revealed that nearly all groundwater samples with δ¹⁵N–NO₃ ⁻ of +7.57 to +13.5‰ were affected by nitrate from manure/sewage as well as microbial nitrification and negligible denitrification. The risk assessment of nitrate for groundwater in the study area was carried out using the risk-based corrective action model since it was recognized that there is a necessity of a quantitative assessment of health hazard, as well as a simple estimation of nitrate concentration. All the groundwaters of higher nitrate concentration than the Korean drinking water standard (<44.3 mg/L NO₃ ⁻) belonged to the domain of the hazard index <1, indicating no health hazard by nitrate in groundwater in the study area. Further, the human exposure to the nitrate-contaminated soil was below the critical limit of non-carcinogenic risk.  相似文献   

Fourier-series representation and projection of spherical harmonic functions   总被引：1，自引：1，他引：0  

Hyeong-Bin Cheong  Ja-Rin Park  Hyun-Gyu Kang 《Journal of Geodesy》2012,86(11):975-990

Computations of Fourier coefficients and related integrals of the associated Legendre functions with a new method along with their application to spherical harmonics analysis and synthesis are presented. The method incorporates a stable three-step recursion equation that can be processed separately for each colatitudinal Fourier wavenumber. Recursion equations for the zonal and sectorial modes are derived in explicit single-term formulas to provide accurate initial condition. Stable computations of the Fourier coefficients as well as the integrals needed for the projection of Legendre functions are demonstrated for the ultra-high degree of 10,800 corresponding to the resolution of one arcmin. Fourier coefficients, computed in double precision, are found to be accurate to 15 significant digits, indicating that the normalized error is close to the machine round-off error. The orthonormality, evaluated with Fourier coefficients and related integrals, is shown to be accurate to O(10^?15) for degrees and orders up to 10,800. The Legendre function of degree 10,800 and order 5,000, synthesized from Fourier coefficients, is accurate to the machine round-off error. Further extension of the method to even higher degrees seems to be realizable without significant deterioration of accuracy. The Fourier series is applied to the projection of Legendre functions to the high-resolution global relief data of the National Geophysical Data Center of the National Oceanic and Atmospheric Administration, and the spherical harmonic degree variance (power spectrum) of global relief data is discussed.  相似文献   

First data on the age of rocks from the northern flank of the Olkhon terrane,western Baikal area     

D. P. Gladkochub  T. V. Donskaya  M. Cho  V. S. Fedorovsky  A. M. Mazukabzov  W. Cheong  J. Kim 《Doklady Earth Sciences》2017,476(1):1021-1025

The metamorphic complexes in the northern part of the Olkhon terrane (Zunduk megazone), Central Asian Fold Belt, are studied. It is found that the age of gneiss–granites, which correspond to granites of type I formed within the active continental margin, is 800 ± 11 Ma, whereas the age of the protolith of epidote–muscovite–feldspar–quartz schist, which formed by metamorphic reworking of island-arc volcanic rocks, is 650–630 Ma. New results and those published earlier show that the structure of the Olkhon terrane contains traces of at least three stages of different ages when suprasubduction processes were manifested. The earliest episode (～850?800 Ma) occurred within the Panthalassa, and the subsequent ones (～650?620 and ～500 Ma) occurred in the Paleoasian Ocean. New data give us grounds to consider protoliths of the studied rocks from the northern flank of the Olkhon metamorphic terrane as products of convergence-related processes that took place within the limits of the paleooceans in the Late Precambrian, rather than in the Pleoproterozoic as was supposed earlier.  相似文献   

Rock Magnetic Approaches Used on Deep-sea Sediments in the Northeastern Equatorial Pacific     

Cheong Kee Park  Gun Chang Lee 《Ocean Science Journal》2018,53(2):369-380

Rock magnetic properties of unconsolidated sediments from the Korea Deep Ocean Study area of the northeastern equatorial Pacific were analyzed to trace the time-dependent variations of sedimentary environments. For upper Pleistocene sediments, light-brown sediments predominate, whereas the lower sediments deposited in the late Pliocene are dark brown. Rock magnetic properties also clearly differ among the two distinct color environments. Values of anhysteretic remanent magnetization and low-field magnetic susceptibility are highly responsive to changes in the color of the sediment. For example, comparatively low values denote a dominance of coarse-grained magnetic minerals as observed in the lower dark-brown layers. With respect to the content of magnetic minerals, coarse magnetic grains are highly concentrated in the darker-colored sediment layers. However, both the magnetic mineral dependent parameter (S ratio) and results of the scanning electron microscope observation indicate that magnetic mineral changes did not occur along the core depth, which means that there was no apparent source change. Without distinctive source changes, the variations in the rock magnetic properties likely reflect a process by which the magnetic grains were primarily transported by enhanced wind and bottom currents and affected by diagenetic dissolution as a function of both the time from burial and the extremely low sedimentation rates after deposition.  相似文献   

Evaluating the impact of visualization of risk upon emergency route-planning     

Lisa Cheong  Christoph Kinkeldey  Ingrid Burfurd  Susanne Bleisch 《International journal of geographical information science》2020,34(5):1022-1050

ABSTRACT

This paper reports on a controlled experiment evaluating how different cartographic representations of risk affect participants’ performance on a complex spatial decision task: route planning. The specific experimental scenario used is oriented towards emergency route-planning during flood response. The experiment compared six common abstract and metaphorical graphical symbolizations of risk. The results indicate a pattern of less-preferred graphical symbolizations associated with slower responses and lower-risk route choices. One mechanism that might explain these observed relationships would be that more complex and effortful maps promote closer attention paid by participants and lower levels of risk taking. Such user considerations have important implications for the design of maps and mapping interfaces for emergency planning and response. The data also highlights the importance of the ‘right decision, wrong outcome problem’ inherent in decision-making under uncertainty: in individual instances, more risky decisions do not always lead to worse outcomes.  相似文献   

Tracking source materials of Phanerozoic granitoids in South Korea by zircon Hf isotopes     

Chang‐sik Cheong  Keewook Yi  Namhoon Kim  Tae‐Ho Lee  Seung Ryeol Lee  Jian‐zhen Geng  Huai‐kun Li 《地学学报》2013,25(3):228-235

Phanerozoic granitoids in South Korea are classified into four primary spatiotemporal groups showing geochemical and isotopic diversity. This study presents the first in situ Hf isotope data for zircons extracted from representative outcrops of each granitoid group. The core‐to‐rim variation in ε_Hf values observed in some zircon grains provides evidence for open‐system processes influenced by the input of more primitive melts or interactions with pre‐existing crustal materials. A general core‐to‐rim decrease in Lu/Hf and Th/U ratios indicates a progressive compositional change in the melts during magmatic differentiation. Contrasting evolutionary paths demonstrated by zircon ε_Hf values suggest that the Neoproterozoic to Palaeozoic crust including the Permian granitoids was recycled during the Cretaceous to Palaeogene magmatism in south‐eastern Korea, whereas the Palaeoarchaean to Palaeoproterozoic crust provided major source material for the Triassic to Jurassic granitoids in central Korea.  相似文献   

Structure change of Typhoon Nari (2007) in the weakening stage     

In-Hyuk Kwon  Hyeong-Bin Cheong  Hyun-Gyu Kang  Hyun-Jun Han  Ja-Rin Park 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(3):327-340

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Enabling maps/location searches on mobile devices: constructing a POI database via focused crawling and information extraction     

Hsiu-Min Chuang  Ting-Yao Kao  Chung-Ting Cheng  Ya-Yun Huang  Kuo-Pin Cheong 《International journal of geographical information science》2016,30(7):1405-1425

With the popularity of mobile devices and smartphones, we have witnessed rapid growth in mobile applications and services, especially in location-based services (LBS). According to a mobile marketing survey, maps/location searches are among the most utilized services on smartphones. Points of interest (POIs), such as stores, shops, gas stations, parking lots, and bus stops, are particularly important for maps/location searches. Existing map services such as Google Maps and Wikimapia are constructed manually either professionally or with crowd sourcing. However, manual annotation is costly and limited in current POI search services. With the abundance of information on the Web, many store POIs can be extracted from the Web. In this paper, we focus on automatically constructing a POI database to enable store POI map searches. We propose techniques that are required to construct a POI database, including focused crawling, information extraction, and information retrieval techniques. We first crawl Yellow Page web sites to obtain vocabularies of store names. These vocabularies are then investigated with search engines to obtain sentences containing these store names from search snippets in order to train a store name recognition model. To extract POIs scattered across the Web, we propose a query-based crawler to find address-bearing pages that might be used to extract addresses and store names. We crawled 1.25 million distinct POI pairs scattered across the Web and implemented a POI search service via Apache Lucent’s search platform, called Solr. The experimental results demonstrate that the proposed geographical information retrieval model outperforms Wikimapia and a commercial app called ‘What’s the Number?’  相似文献