• Economic and Environmental Geology
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• v.7 no.1
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• pp.1-21
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• 1974

From the point of view of geological history, the land of South Korea is regarded as the subject of processes of the changes in formations of several geological blocks such as Kyonggi massif, Yeongnam massif, Taebaegsan basin, Kyungsang basin and so on. Through the long period of geological chronology, the present topography and geotectonics have been formed by the complicate interactions of epirogenetic movements, magmatism, orogenesis, differential vertical movements, metamorphism and sedimentation. The reason of the crust movements mentioned above, is suppossed that the Pacific and West Pacific plate have subducted directly or indirectly into the East Asia plate. This fact can be endorsed by the results of the studies on the heat flow, gravity anomaly, absolute age dating, tectonic lineation, lithofacies and the temperature of hot spring in South Korea. The formations of metal ore deposits as well as other geological processes can be determined by the mechanical control of the plates and be divided into several systematic patterns. The investigation of about 110 metal mines in South Korea shows the following results. (1) Plate boundary volcanic type is about 28% (2) Plate boundary plutonic type is about 44% (3) Intraplate sedimentary type is about 26% (4) Intraplate magmatic type is about 2%.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.11
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• pp.989-995
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• 2015

In the literature, various stochastic anomaly detection methods, such as limit checking and PCA-based approaches, have been applied to weld defect detection. However, it is still a challenge to identify meaningful defect patterns from very limited sensor signals of laser welding, characterized by intermittent, discontinuous, very short, and non-stationary random signals. In order to effectively analyze the physical characteristics of laser weld signals: plasma intensity, weld pool temperature, and back reflection, we first transform the raw data of laser weld signals into the form of event logs. This is done by multidimensional discretization and event-codification, after which the event logs are decoded to extract weld defect patterns by $Na{\ddot{i}}ve$ Bayes classifier. The performance of the proposed method is examined in comparison with the commercial solution of PRECITEC's LWM$^{TM}$ and the most recent PCA-based detection method. The results show higher performance of the proposed method in terms of sensitivity (1.00) and specificity (0.98).

• Journal of Magnetics
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• v.17 no.3
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• pp.168-171
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• 2012

Irreversible magnetization between the zero-field-cooled (ZFC) and field-cooled (FC) states in $Y_{1-x}Sr_xMnO_3$ (x=0 and 0.2) was investigated. $YMnO_3$ and $Y_{0.8}Sr_{0.2}MnO_3$ have a hexagonal structure and the lattice parameter a decreases from 7.4408 ${\AA}$ to 7.4327 ${\AA}$ while c increases from 12.2244 ${\AA}$ to 12.2287 ${\AA}$ for $YMnO_3$ and $Y_{0.8}Sr_{0.2}MnO_3$, respectively. An anomaly is observed at around 74 K in ZFC and FC magnetization measurements for $YMnO_3$, whereas in $Y_{0.8}Sr_{0.2}MnO_3$ the ${\sigma}_{ZFC}$ and ${\sigma}_{FC}$ are split at low temperature, indicating glass-like behavior.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3164-3182
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• 2023

The CRUD on the fuel cladding under the pressurized water reactor (PWR) operating condition causes several issues. The CRUD can act as thermal resistance and increases the local cladding temperature which accelerate the corrosion process. The hideout of boron inside the CRUD results in axial offset anomaly and reduces the plant's shutdown margin. Recently, there are efforts to revise the acceptance criteria of emergency core cooling systems (ECCS), and additionally require the modeling of the thermal resistance effect of the CRUD during the performance analysis. There is an urgent need for the evaluation of the effect of the CRUD deposition on the cladding heat transfer under PWR operating conditions, but the experimental database is very limited. The experimental facility called DISNY was designed and constructed to analyze the CRUD-related multi-physical phenomena, and the performance analysis of the constructed DISNY facility was conducted. The thermal-hydraulic and water chemistry conditions to simulate the CRUD growth under PWR operating conditions were established. The design characteristics and feasibility of the DISNY facility were validated by the MARS-KS code analysis and separate performance tests. In the current study, detailed design features, design validation results, and future utilization plans of the proposed DISNY facility are presented.

• International Journal of Computer Science & Network Security
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• v.24 no.6
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• pp.67-76
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• 2024

The Internet of Things (IoT) has revolutionized communication and device operation, but it has also brought significant security challenges. IoT networks are structured into four levels: devices, networks, applications, and services, each with specific security considerations. Personal Area Networks (PANs), Local Area Networks (LANs), and Wide Area Networks (WANs) are the three types of IoT networks, each with unique security requirements. Communication protocols such as Wi-Fi and Bluetooth, commonly used in IoT networks, are susceptible to vulnerabilities and require additional security measures. Apart from physical security, authentication, encryption, software vulnerabilities, DoS attacks, data privacy, and supply chain security pose significant challenges. Ensuring the security of IoT devices and the data they exchange is crucial. This paper utilizes the Random Forest Algorithm from machine learning to detect anomalous data in IoT devices. The dataset consists of environmental data (temperature and humidity) collected from IoT sensors in Oman. The Random Forest Algorithm is implemented and trained using Python, and the accuracy and results of the model are discussed, demonstrating the effectiveness of Random Forest for detecting IoT device data anomalies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.6
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• pp.557-565
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• 1984

The year-to-year fluctuations of seasonal variation of sea surface temperatures (SST) in the Korea Strait are studied based on monthly SST data for more than 50 years at Mitsushima ana Okinoshima in the strait. The frequency distribution of SST has two peaks at temperatures below and above the multi-year average, but that of SST anomalies has only one peak at the zero anomaly. More than $95\%$ of the anomalies are in the range of ${\pm}2^{\circ}C$. The harmonic constansts of seasonal SST variation vary from year to year. The standard deviations of annual means, annual amplitudes, ana semi-annual amplitudes are less than $1^{\circ}C$, and those of the annual ana semi-annual phases are about $5^{\circ}$ and less than $50^{\circ}$, respectively. The SST in the Korea Strait have a tendency to decrease their amplitudes as the annual means increase. Physical mechanisms responsible for the analyzed results are discussed in this paper.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.294-298
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• 2008

Snow cover is a potential water resource for later spring and summer seasons as well as a thermal mirror with high reflectivity causing decreases of surface air temperature during cold winter seasons. In this study, current and future changes in Northern Hemisphere snow extent and their potential linkages with atmospheric circulation are examined. The NOAA AVHRR visible snow extent (1967-2006) data as well as observational (NCEP-DOE 1979-2006) and modeled (GFDL 2.1 2081-2100) pressure and surface air temperature data are used. Analyses of observational data demonstrate that the snow extent in meteorological spring (March to April) and summer (June to August) has significantly decreased since the late 1980s. The offset of snow seasons (the timing of snow melt in spring) have also significantly advanced particularly in Europe, East Asia, and northwestern North America. Analyses of pressure fields reveal that the spatial patterns of the earlier snow melt are associated with changes in atmospheric circulation such as the Arctic Oscillation (AO). In the positive winter AO years, multiple positive pressure departure cores in the upper troposphere (200hPa) are observed over the mid-latitude regions from March to mid-April, while a negative pressure departure core (70hPa) prevails over the Arctic Ocean. The reversed anomaly patterns related to later snow melt occur in negative winter AO years. The comparison between current and future thermal spring onsets suggest that snow melt patterns will intensify with larger greenhouse gas emissions, indicating earlier hydrological spring onset.

• Environmental and Resource Economics Review
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• v.25 no.4
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• pp.471-494
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• 2016

This study investigates the effect of remittance and agricultural aid inflows on GDP growth rate volatility in response to climate change shocks in twenty-eight African countries by using system generalized method of moments from 1996 to 2013 with three years grouped data. The climate change shocks are indicated by four variables; natural disasters, rainfall variability, fluctuation in temperature and the weighted anomaly standardized precipitation (WASP) index. Consequently, natural disasters and temperature variability have a significant effect on GDP volatility, while rainfall variability and WASP index have no adverse consequence on stabilization of the economy. On the other hand, in general, remittances and agricultural aid are helpful to stabilize the economy and especially remittances inflows can play a crucial role as insurance when natural disasters occur.

• Journal of the Korean earth science society
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• v.39 no.5
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• pp.403-418
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• 2018

This study conducted synoptic and mesoscale analyses to understand the cause of Japan Tsukuba tornado development, which occurred at 0340 UTC 6 May 2012. Prior to the tornado occurrence, there was a circular jet stream over Japan, and the surface was moist due to overnight precipitation. The circular jet stream brought cold and dry air to the upper-level atmosphere which let strong solar radiation heat the ground with clearing of sky cover. A tornadic supercell developed in the area of potentially unstable atmosphere. Sounding data at Tateno showed a capping inversion at 900 hPa at 0000 UTC 6 May. Strong insolation in early morning hours and removal of the inversion instigated vigorous updraft with rotation due to vertical shear in the upper-level atmosphere. This caused multiple tornadoes to occur from 0220 to 0340 UTC 6 May 2012. When comparing Tateno's climatological temperature and dew-point temperature profile on the day of event, the mid-level atmosphere was moister than typical sounding in the region. This study showed that tornado development in Tsukuba was caused by a combination of (a) topography and potential vorticity anomaly, which increased vorticity over the Kanto Plain; (b) vertical shear, which produced horizontal vortex line; and c) thermal instability, which triggered supercell and tilted the vortex line in the vertical.

• Economic and Environmental Geology
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• v.29 no.5
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• pp.545-559
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• 1996

Rare metal (Nb-Zr-REE) ore deposits are located in the Chungju area. Geotectonically, the rare metal ore deposits are situated in the transitional zone between Kyeonggi massif and Okcheon belt. The rare metal deposits are distributed in Kyemyeongsan Formation which consist of schist and alkaline igneous rocks. Alkali granite has suffered extensive post-magmatic metasomatism and hydrothermal processes. The ore contains mainly Ce-La, Ta-Nb, Y, Y-Nd, Nd-Th group minerals. More than 15 RE and REE minerals are found in the ore deposits. Allanite, one of the Ce-La rich REE minerals belonging to the epidote group, is the most common mineral in the studied area. The allanite- bearing rocks may be devided into seven types by features of occurrence and mineral associations; zircon type (ZT), allanite-vein type (AT), feldspar type (KT), fluorite type (FT), quartz-mica type (QT), iron-oxide type (MT), and amphibole type (HT). The allanite veins (AT) and zircon rich rocks (ZT) contain the highest total REE contents. Differences in REE abundance can be interpreted in terms of varying portions of magmatic hydrothermal fluid. Petrographical and chemical data are presented for allanites which were collected from different types. The allanites show wide variations in optical properties, due in part to differences in their chemical composition (depending on the types) and to the degree of crystallinity of the individual specimens. Allanite metamicts in biotite are generally surrounded by well developed pleochroic haloes. Usually, allanite is accompanied by zircon and other REE-bearing minerals. CaO and total REE contents $({\sum}RE_2O_3)$ range from 9.29 to 18.79% and 11.66 to 26.31%, respectively. Also, SiO, (28.87~32.61%), $Al_2O_3$ (8.30~16.88%), and $Fc_2O_3$ (16.74~24.38%) contents show varying contents from type to type. The ${\sum}RE_2O_3$ of allanite has positive relationships with $Fe_2O_3$ and negative relaton with CaO, $SiO_2$, and $Al_2O_3$ Backscattered electron microscope images (BEl) of allanite shows that the its mineral composition and texture is very complex. The allanite-bearing hosts show distinct light REE enrichment with strong negative Eu anomaly except for HI. The HT has an almost flat REE distribution pattern with a small negative Eu anomaly. The chemical variation of the allanites with occurrences and mineral association can be related to condition of temperature and oxidation states in precipitation environment.