• Analytical Science and Technology
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• v.25 no.1
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• pp.25-32
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• 2012

Isotope dilution mass spectrometry (ID-MS) based on liquid chromatography tandem mass spectrometry (LC/MS/MS) was developed for the accurate determination of sorbic acid in tea-drink. An isotope analogue of sorbic acid, $^{13}C_2$-sorbic acid, was obtained by custom synthesis. MS was operated in the negative mode with selected reaction monitoring (SRM) mode of $[M-H]^-$ ${\rightarrow}$ $[M-CO_2H]^-$ channel at m/z 111 ${\rightarrow}$ 67 for sorbic acid and at m/z 113 ${\rightarrow}$ 68 for its isotope analogue. Chromatographic separation was accomplished with a C18 column and an isocratic mobile phase of 55% of 50 mM ammonium acetate (pH 4.5) and 45% of methanol. Homogeneous reference materials were prepared for validation of this method, including repeatability and reproducibility tests, by fortifying tea-drink with sorbic acid in our laboratory. Repeatability and reproducibility studies showed that the ID-LC/MS method is a reliable and reproducible method which provides less than 3.8% of relative standard deviation (RSD) for the analysis of sorbic acid.

• Analytical Science and Technology
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• v.18 no.4
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• pp.271-277
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• 2005

Urea in blood has been measured as an effective marker for diagnosis of renal function. Urea which is e end-product of nitrogen containing metabolites such as proteins is filtered through glomeruli of kidneys and then excreted as urine. If the renal function is deteriorated, the urea concentration in blood will be increased, from which the healthiness of renal function is judged. In order to improve the confidence of diagnosis results, the results must keep traceability chain to certified reference materials, which was certified by primary reference method. In this study, we proposed isotope dilution-liquid chromatography/mass spectrometry (ID-LC/MS) as a candidate primary method, in which $15^N_2$-urea is used as an internal reference material. The developed method is highly accurate in principle and is convenient as it does not require cumbersome derivatization. 0.1 mmol/L ammonium chloride was selected as a mobile phase for HPLC because it provided low interference in MS analysis of relatively low molecular weighted urea. HPLC and MS were connected with an electrospray ionization (ESI) interface of positive mode, which provided high sensitivity and reproducibility. The developed method was validated with internationally recognized reference materials, and we have obtained satisfactory results in an international ring trial. The expanded uncertainty calculated according to ISO guide was 1.8% at 95% confidence interval. The developed method is being used as a primary reference measurement method such as for certification of serum certified reference materials (CRMs).

• Land and Housing Review
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• v.4 no.1
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• pp.43-54
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• 2013

This This paper investigates the variation of the factors to determinate housing price in Seoul metropolitan area after sub-prime financial crisis, in Korea, using a VAR model. The model includes housing price and housing rent (Jeonse) in Seoul metropolitan area from 1999 to 2011, and uses interest rate, real GDP, KOSPI, Producer Price Index and practices to impulse response and variance decomposition analysis to grasp the dynamic relation between a variable of macro economy and and a variable of housing price. Data is classified to 2 groups before and after the 3rd quater of 2008, when sub-prime crisis occurred; one is from the 1st quater of 1999 to the 3rd quater of 2008, and the other is from the 2nd quater of 1999 and the 4th quater of 2011. As a result, comparing before and after sub-prime crisis, housing price is more influenced by its own variation or Jeonse price's variation instead of interest rate and KOSPI. Both before and after sub-prime financial crisis, Jeonse price is also influenced by its own variation and housing price. While after sub-prime financial crisis, influences of Producer Price Index, KOSPI and interest rate were weakened, influence of real GDP is expanded. As housing price and housing rent are more influenced by real economy factors such as GDP, its own variation than before sub-prime financial crisis, the recent trend that the house prices is declined is difficult to be converted, considering domestic economic recession and uncertainty, continued by Europe financial crisis. In the future to activate the housing business, it ia necessary to promote purchasing power rather than relaxation of financial and supply regulation.

• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.243-248
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• 2010

Sonic nozzles have been a standard device for measurement of steady state gas flow, as recommended in ISO 9300. This paper introduces two sonic nozzles of diameter ${\Phi}$ 0.03 mm and ${\Phi}$ 0.2 mm precisely machined according to ISO 9300. The constant volume flow meter(CVFM), readily set up in the Vacuum center of KRISS. was used to calibrate the discharge coefficients of both nozzles. The calibration results were shown to determine them within the 3% expanded measurement uncertainty. Calibrated sonic nozzles were found to be applicable for precision measurement of steady state gas flow in the vacuum process in the ranges of 0.6~1,800 cc/min. Those flow conditions are equivalent to the fine gas flow with Reynolds numbers of 26~12,100. Those encouraging results confirm that calibrated sonic nozzles enable precision measurement of extremely low gas flow encountered very often in th vacuum processes. Both calibrated sonic nozzles are proven to provide the precision measurement of the volume flow rate of the dry vacuum pump within one percent difference in reference to CVFM. Calibrated sonic nozzles are applied to a new 'in-situ and in-field' equipment designed to measure the volume flow rate of vacuum pumps in the semiconductor and flat display processes. Furthermore, they can provide other applications to flow control devices in vacuum, such as MFC, etc.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.221-232
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• 2009

The geographical distribution of freeze risk determines the latitudinal and altitudinal limits and the maximum acreage suitable for fruit production. Any changes in its pattern can affect the policy for climate change adaptation in fruit industry. High-definition digital maps for such applications are not available yet due to uncertainty in the combined responses of temperature and dormancy depth under the future climate scenarios. We applied an empirical freeze risk index, which was derived from the combination of the dormancy depth and threshold temperature inducing freeze damage to dormant buds of 'Changhowon Hwangdo' peach trees, to the high-definition digital climate maps prepared for the current (1971-2000), the near future (2011-2040) and the far future (2071-2100) climate scenarios. According to the geospatial analysis at a landscape scale, both the safe and risky areas will be expanded in the future and some of the major peach cultivation areas may encounter difficulty in safe overwintering due to weakening cold tolerance resulting from insufficient chilling. Our test of this method for the two counties representing the major peach cultivation areas in South Korea demonstrated that the migration of risky areas could be detected at a sub-grid scale. The method presented in this study can contribute significantly to climate change adaptation planning in agriculture as a decision aids tool.

• Journal of the Korean Society of Earth Science Education
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• v.13 no.3
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• pp.238-252
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• 2020

In this study, we analyzed the types of rebuttals in the argument structure of learning contents in lesson plans constructed by Earth science preservice teachers, and then we explored examples of how they responded to resolving the rebuttal. As a result of analyzing preservice teachers' assignments, discussions, and interviews collected during a total of 20 hours of classes and group discussions for 5 weeks, all 5 types of rebuttals suggested by Verheij (2005) were identified. Through the data analysis, a total of 18 rebuttal cases derived, and these cases were classified into 3 types according to how preservice teachers solve the rebuttals in class. The conclusions and implications based on the results are as follows: First, this study provided empirical data that the thinking process of validating core elements of argumentation and processes of argumentation is actively taking place in preservice teachers' lesson planning using the argument structure, and expanded the scope of application of argumentation in science education research. Second, the argument structure of learning contents should be used to help teachers to come up with strategies to induce students' curiosity and devotion to learn science contents. Third, preservice teachers should have the opportunity to think about the nature of science, including the variability and uncertainty of scientific knowledge when they discover rebuttals and develop solutions to them. Based on these conclusions, implications and suggestions for science education and further research were suggested.

• Journal of Korea Water Resources Association
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• v.55 no.1
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• pp.43-57
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• 2022

Advances in measurement techniques have reduced measurement costs and enhanced safety resulting in less uncertainty. For example, an acoustic doppler current profiler (ADCP) based suspended sediment concentration (SSC) measurement technique is being accepted as an alternative to the conventional data collection method. In Korean rivers, horizontal ADCPs (H-ADCPs) are mounted on the automatic discharge monitoring stations, where SSC can be measured using the backscatter of ADCPs. However, automatic discharge monitoring stations and sediment monitoring stations do not always coincide which hinders the application of the new techniques that are not feasible to some stations. This work presents and analyzes H-ADCP-SSC models for 9 discharge monitoring stations in Korean rivers. In application of the Gaussian mixture model (GMM) to sediment-related variables (catchment area, particle size distributions of suspended sediment and bed material, water discharge-sediment discharge curves) from 44 sediment monitoring stations, it is revealed that those characteristics can distinguish sediment monitoring stations regionally. Linking the two results, we propose a protocol determining the H-ADCP-SSC model where no H-ADCP-SSC model is available.

• The Journal of the Korea Contents Association
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• v.21 no.7
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• pp.281-290
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• 2021

The scope of fire services has been expanded from local fire prevention to rescue and first aid services, and the fire services system has been converted from an autonomous fire services system to a wide-area fire services system, and the status of fire officers has been unified as a national public servant. However, the underlying problem remains unsolved. One is a problem related to the conversion of fire services to state affairs, and the other is that Fire officers converted to national public servants are in charge of fire services which are evaluated as local autonomous affairs. The controversy over the nature of fire service stems from uncertainty and redundancy in the coordination of office function and distribution between the State and Local governments, and incomplete legislation that fundamentally fails to achieve systematic unity of office work and status. The fire service has a national responsibility as an affair that includes the existence of the state and the welfare and order of the people along with the police affairs. That is, affairs related to the safety of the people that protect the lives, bodies and properties of the people should be understood as State affairs. 「The LOCAL AUTONOMY ACT」 stipulates that local governments cannot perform State affairs such as affairs necessary for the existence of the nation, affairs requiring performance in a uniform manner throughout the nation, and affairs of nationwide or similar scale unless otherwise provided by the law. Fire Service should be regarded as such affairs. Considering that the rights to the safety and life of the people and the duty to protect the people are the duty of the nation, it is necessary to keep in mind that the reason for the change fire officers to the national public servants was not basically just a matter of treatment and finance.

• Analytical Science and Technology
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• v.21 no.4
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• pp.316-325
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• 2008

An inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with flow injection-hydride generation system was used for the determination of trace arsenic in seawater sample. The accuracy in this method was verified by the analysis of certified reference materials (CRM) of seawater (CASS-4, NASS-5). The analytical results agreed with certified value within the range of uncertainty. The expanded uncertainties for CASS-4 and NASS-5 in this experiment were ranged from 6.2% to 6.8% obtained from repeated analyses of the CRMs (n=5). The detection limit of $As^+$ (m/z=74.9216) in this method was confirmed about 0.01 ug/kg. Linearity obtained from calibration curve of arsenic was excellent ($R^2=1$). The detection at $As^+$ (m/z=74.9216) and $AsO^+$ (m/z=90.9165) by using oxygen reaction gas in DRC mode was compared. Sensitivity at $AsO^+$ (m/z=90.9165) was decreased about 25-fold, but the analytical results are the same that at $As^+$ (m/z=74.9216).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.100-103
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• 2023

Recently, development of maritime autonomoust surface ships and eco-friendly ships, production and evaluation research considering various marine environments is needed in the field of optimal routes as the demand for accurate and detailed real-time marine environment prediction information expands. An algorithm that can calculate the optimal route while reducing the risk of the marine environment and uncertainty in energy consumption in smart ships was developed in 2 stages. In the first stage, a profile was created by combining marine environmental information with ship location and status information within the Automatic Ship Identification System(AIS). In the second stage, a model was developed that could define the marine environment energy map using the configured profile results, A regression equation was generated by applying Random Forest among machine learning techniques to reflect about 600,000 data. The Random Forest coefficient of determination (R²) was 0.89, showing very high reliability. The Dijikstra shortest path algorithm was applied to the marine environment prediction at June 1 to 3, 2021, and to calculate the optimal safety route and express it on the map. The route calculated by the random forest regression model was streamlined, and the route was derived considering the state of the marine environment prediction information. The concept of route calculation based on real-time marine environment prediction information in this study is expected to be able to calculate a realistic and safe route that reflects the movement tendency of ships, and to be expanded to a range of economic, safety, and eco-friendliness evaluation models in the future.