• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.58.4-59
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• 2015

We have performed single dish and VLBI monitoring observations of $H_2O$ and SiO masers toward the semi-regular variable star R Crateris using the Korean VLBI Network(KVN) 4 band receiving system. In the case of VLBI observations at 3 epochs, successful superposed maps of $H_2O$ and SiO masers were obtained on 2015 May by adopting the Source Frequency Phase Referencing(SFPR) method. These results enable us to investigate the development of outflow and asymmetric motions from SiO maser to $H_2O$ maser regions according to stellar pulsation which are closely related with a mass-loss process. Single dish monitoring observations were carried out from 2009 June to 2015 May. Intensity variations between $H_2O$ and SiO masers were investigated according to stellar phases together with peak velocity variations. We will compare the VLBI results with those of single dish.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.18-25
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• 2012

For effective watershed management, it is very important to select the tributaries through selection and concentration of targeted tributary catchments for improving water quality within the limited financial conditions. This study introduced the selection and diagnosis procedure of tributary catchments for improving water quality at Chungcheongnam-do based on water quality and flowrate monitoring, stream grouping method. The tributaries with high value of water quality and flowrate were selected for improving water quality according to stream grouping method. The diagnosis of selected tributaries for improving water quality was performed with analysis of the pollution load (generated, discharged, delivered) and point source discharged pollution load density. The plans for improving water quality of tributaries were suggested thorough various diagnosis of tributary catchments. For improving water quality of tributaries in Chungcheongnam-do, the tributary catchments in the Dangjin, Asan, Yesan, Cheonan, Hongseong area should be preferentially considered. The water quality improving plans for those tributary catchments, in accordance with the reduction of sources of pollution by population and livestock, should be established.

• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.309-316
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• 2013

The Non-Point Sources shows different characteristics over a wide area depending on basin situation and rainfall events etc. In addition, Among various land uses in the urban areas, runoff appears high in the paved area, though small in its size, during a heavy rain than in other land use owing to its high impervious rate, and pollutants become severly accumulated owing to continual transportation of vehicles, characteristically showing high concentrations of runoff in the early stage. As a result, several advanced countries including USA give a special emphasis on the paved area as a target for supervision. In view of these aspects, the research is not only required to consider separated sub-basins which are distributed according to land uses, but also needed to develop a suitable monitoring which is reflected rainfall-runoff relation. The on-site monitoring has been performed to collect data in object watershed as well.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1689-1696
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• 2017

In recent academic and industrial circles of the Republic of Korea, the securement of available reactive power reserve against the line faults is at issue. Thus, simulations have been performed for the securing of effective reactive power reserve (effective Q) to prepare for the line faults and improve reactive power monitoring and control methods. That is, a research has been conducted for the fast-decoupled Newton-Raphson method. In this study, a method that distinguishes source and sink regions to carry out faster provision of information in the event of line fault has been proposed. This method can perform quantification with the formula that calculates voltage variations in the line flow. The line flow and voltage changes can be easily induced by the power flow calculation performed every second in the operation system. It is expected that the proposed method will be able to contribute to securement of power system stability by securing efficient reactive power. Also, the proposed method will be able to contribute to prepare against contingencies effectively. It is not easy to prepare quickly for the situation where voltage drops rapidly due to the exhaustion of reactive power source by observing voltage information only. This paper's simulation was performed on the large scale Korean power system in steady state.

• Asian Journal of Atmospheric Environment
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• v.6 no.1
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• pp.23-32
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• 2012

The ionic composition of $PM_{2.5}$ samples was investigated by their datasets of cationic ($Na^+$, $NH_4^+$, $K^+$, $Mg^{2+}$, and $Ca^{2+}$) and anionic components ($Cl^-$, $NO_3^-$, and $SO_4^{2-}$) along with relevant environmental parameters collected from an urban monitoring site in Korea at hourly intervals in 2010. The mean (and SD) annual concentration of $PM_{2.5}$ was computed as 25.3 ${\mu}g\;m^{-3}$ with the wintertime maximum. In addition, sum concentrations (neq $m^{-3}$) of five cationic species (291) were slightly lower than 3 anionic species (308). Most cations exhibited the highest seasonal values in spring, while anions showed more diversified seasonal patterns. According to PCA, five major source categories were apparent with the relative dominance of secondary inorganic aerosols (SIA). The results of our study suggest consistently that the distribution of ionic constituents in an urban area is affected by the combined effects of both natural and anthropogenic processes.

• Journal of Astronomy and Space Sciences
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• v.30 no.2
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• pp.107-112
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• 2013

Tissue equivalent proportional counter (TEPC) can measure the Linear Energy Transfer (LET) spectrum and calculate the equivalent dose for the complicated radiation field in space. In this paper, we developed and characterized a TEPC for radiation monitoring in International Space Station (ISS). The prototype TEPC which can simulate a 2 ${\mu}m$ of the site diameter for micro-dosimetry has been tested with a standard alpha source ($^{241}Am$, 5.5 MeV). Also, the calibration of the TEPC was performed by the $^{252}Cf$ neutron standard source in Korea Research Institute of Standards and Science (KRISS). The determined calibration factor was $k_f=3.59{\times}10^{-7}$ mSv/R.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1606-1608
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• 2001

In connection with the monitoring of the insulation degradation of the large power apparatus, a statistical treatment, such as phase resolved partial discharge analysis (PRPDA) has been established for the on-line monitoring system during the past two decades. However, it has shown some inconveniences to distinguish the nature of the PD source in power apparatus. In this regard, a novel approach based on the chaotic analysis(CAPD) is proposed describing the fundamental ideas, outcomes and different view points from conventional PRPDA. In order to make a model for the possible defects causing sudden failures in service, several types of specimen were prepared. And partial discharge signals, originated from those samples, were measured and analyzed by means of PRPDA and CAPD respectively. In this paper, it seems that the correlation between the consecutive PD pulses depending on the nature of PD could be investigated by CAPD. Therefore, it could be considered that the nature of PD source can be distinguished more distinctively when the PRPDA is combined with CAPD.

• International Journal of Concrete Structures and Materials
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• v.9 no.3
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• pp.307-321
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• 2015

The primary objective of this study is to investigate the feasibility of an innovative surface-mount sensor, made of a piezoelectric disc (PZT sensor), as a consistent source for surface wave velocity and transmission measurements in concrete structures. To this end, one concrete slab with lateral dimensions of 1500 by 1500 mm and a thickness of 200 mm was prepared in the laboratory. The concrete slab had a notch-type, surface-breaking crack at its center, with depths increasing from 0 to 100 mm at stepwise intervals of 10 mm. A PZT sensor was attached to the concrete surface and used to generate incident surface waves for surface wave measurements. Two accelerometers were used to measure the surface waves. Signals generated by the PZT sensors show a broad bandwidth with a center frequency around 40 kHz, and very good signal consistency in the frequency range from 0 to 100 kHz. Furthermore, repeatability of the surface wave velocity and transmission measurements is significantly improved compared to that obtained using manual impact sources. In addition, the PZT sensors are demonstrated to be effective for monitoring an actual surface-breaking crack in a concrete beam specimen subjected to various external loadings (compressive and flexural loading with stepwise increases). The findings in this study demonstrate that the surface mount sensor has great potential as a consistent source for surface wave velocity and transmission measurements for automated health monitoring of concrete structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.4
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• pp.215-220
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• 1999

Concrete micro-cracks that are grown while the structures are under construction or in service, propagate gradually or rapidly by external forces and environmental effects. As described above, almost concrete structures generally have cracks, so for the safety and durability of structures, studies to detect cracks using nondestructive tests have been treated in great deal. The purpose of this study is to evaluate characteristics of AE signals detected from notched concrete beams bending test with different loading using one of nondestructive test, Acoustic Emission (AE) method. Furthermore this study predicts the location of initial crack and measures direction of crack propagation for on-line monitoring before the crack really grows in structures by using two-dimensional AE source location based on rectangular method with three-point bending test. This will allow efficient maintenance of concrete structures through monitoring of internal cracking based on acoustic emission method.

• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.3
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• pp.29-38
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• 2018

It is the approach of embedded system design that analyzes COS(Cut Out Switch) failure in the power distribution and an instantaneous breakdown of power distribution supply could cause the weakness of industrial competence and therefore we need to feed the stable power distribution with developing the technology of open-source embedded system. In this paper, we apply the LoRa technology which is the Internet of Things(IoT) protocol for low data rate, low power, low cost and long range sensor applications. We designed the hardware and software architecture setup and experimented the embedded system with network architecture and COS monitoring system including accelerometer for detecting the failure of distribution line and sensing the failure of its fuse holder by recognizing the variation and collision and afterwards sending the information to a gateway. With experimenting we designed the embedded platform for sensing the variation and collision according to the COS failure, monitoring its fuse holder status and transferring the information of states with LoRa technology.