• Journal of the Korean Society of Radiology
• /
• v.16 no.6
• /
• pp.709-718
• /
• 2022

We evaluated the effect of high-density aluminum, titanium, and steel metal inserts on computed tomography (CT) numbers and radiation treatment plans for Tomotherapy. CT images were obtained using a cylindrical TomoPhantom comprising cylindrical rods of various densities and metal inserts. Three CT image sets were evaluated for image quality as the mean CT number and standard deviation. Dose evaluation also performed. The reference values did not significantly differ between the CT image sets with the corrected metal inserts. The higher-density material exhibited the largest difference in the mean CT number and standard deviation. The conformity index at Iterative-Metal Artifact Reduction (iMAR) was approximately 20% better than that of non-iMAR. No significant target or organ at risk dose difference was observed between non-iMAR and iMAR. Therefore, iMAR is helpful for target or organ at risk delineation and for reducing uncertainty for three-dimensional conformal radiation therapy in Tomotherapy.

• The Korea Journal of Herbology
• /
• v.28 no.3
• /
• pp.61-68
• /
• 2013

Objectives : A precise and simple system of nomenclature was required to avoid error, ambiguity or confusion. Although medicinal plants must be produced or distributed based on a pharmacopoeia described origin including scientific name, the Korean Pharmacopoeia tenth edition (KP 10) had many names against the nomenclature. Therefore, this study aimed at searching correct scientific names for 241 plants in KP 10. Methods : Authoritative databases - The Plant List, International Plant Name Index, YList, Tropicos, eFloras, World Checklist of Selected Plant Families, The Global Compositae Checklist, The International Legume Database and Information Service, et al. - and previously performed researches, floras were cross-checked. Results : The arrangement of this list was designed for four cases, errors including illegitimate, nomenclatural synonyms, recommended names and decision reserved names. Consideration about the scientific names produced nine correct names for ten misspellings and illegitimate, and thirty-six correct names for forty-one nomenclatural synonyms. These results should be reflected in the next of KP 10. Separately, ten recommended names were also suggested for taxonomic synonyms which had been used indiscriminately due to diverse taxonomic opinions. In addition to those, decision reserved names were suggested for thirteen species which had been corridor of uncertainty. Then again, there was need to study about authorship, because KP 10 did not keep recommendations for author citations. Conclusions : Correction of scientific names for some medicinal plants which violated the International Code of Nomenclature would be useful to improve the accuracy of a Pharmacopoeia as the criterional materials.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5C
• /
• pp.343-350
• /
• 2006

The resistance bias factors for driven steel pipe piles are evaluated as a part of study to develop the LRFD(Load and Resistance Factor Design) for foundation structures in Korea. The 43 data sets of static load tests and soil property tests performed in the whole domestic area were collected and analyzed to determine the representative bearing capacities of the piles using various methods. Based on the statistical analysis of the data, the Davisson's criterion is proved to be the most reasonable method for estimation of pile bearing capacity among the methods used. The static bearing capacity formulas and the Meyerhof method using N values are applied to calculate the design bearing capacity of the piles. The resistance bias factors of the driven steel pipe piles are evaluated respectively as 0.98 and 1.46 by comparison of the bearing capacities for both of the static bearing capacity formulas and the Meyerhof method. It is also shown that uncertainty of the static bearing capacity formulas is relatively less than that of the Meyerhof method.

• Korea Trade Review
• /
• v.47 no.4
• /
• pp.215-231
• /
• 2022

Analysis and forecasting of the Baltic Capsize Index (BCI) is important for managing an entity's losses and risks from the uncertainty and volatility of the fast-changing maritime transport market in the future. This study conducted volatility transition analysis through the GARCH model, using BCI which is highly related to steel raw materials. As for the data, 2,385 monthly data were used from March 1999 to March 2021. In this study, after basic statistical analysis, unit root and cointegration test, the GARCH, EGARCH, and DCC-GARCH models were used for volatility transition analysis. As the results of GARCH and EGARCH model, we confirmed that all variables had no autocorrelation between the standardized residuals for error terms and the square of residuals, that the variability of all variables at this time was likely to persist in the future, and that the variability of the time-series error term impact according to Iron ore trade (IoT). In addition, through the EGARCH model, the magnitude convenience of all variables except the Iron ore price (IOP) and Capesize bulk fleet (BCF) variables was greater than the positive value (+). As a result of analyzing the DCC-GARCH (1,1) model, partial linear combinations were confirmed over the entire period. Estimating the effect of variability transition on BCF and C5 with statistically significant linear combinations with BCI confirmed that the impact of BCF on BCI was greater than the impact of BCI itself.

• Korea Trade Review
• /
• v.46 no.2
• /
• pp.19-38
• /
• 2021

This study aims to analyze the foreign asset leverage effect on Korean oil & gas companies' foreign profits and to maintain the appropriate foreign asset volume for reducing exchange risk. For a long time, large Korean companies, including oil companies, overheld foreign currency liabilities. For this reason, most large companies have been burdened to hedge exchange risk and this excess limit holding deteriorated total profit and reduced foreign currency asset management efficiency. Our paper proceeds in presenting a three-stage analysis considering diversified exchange risk factors through estimation on transformation of foreign transactions a/c including annual trends of foreign asset and industry specifics. We also supplement incomplete the estimation method through a practical hedging case investigation. Our research parts are differentiated on the analyzing four periods considering period-specifics The FER value of the oil firms ranged from -0.3 to +2.3 over the entire period. The results of the FER Value are volatile and irregular; those results do not represent the industry standard comparative index. The Korean oil firms are over the credit limit without accurate prediction and finance high interest rate funds from foreign-owned banks on the basis on a biased relationship. Since the IMF crisis, liabilities of global firms have decreased. Above all, oil firms need to finance a minimum limit without opportunity losses on the demand forecast and prepare for uncertainty in the market. To reduce exchange risk from the over-the-limit position, we must consider factors that affect the corporate exchange risk on the entire business process, including the contract phase.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.4
• /
• pp.202-208
• /
• 2005

In Korea it tends to rely on foreign standards for the stability management of the embankment slope on the soft clay layer. The Matsuo-Kawamura's method, the Kurihara's method, the Tominaga- Hashimoto's method and the Shibata-Sekiguchi's method are generally employed at site. In this study these slope stability methods are investigated and the applicability of the stability management methods is evaluated through numerical analysis. It is evaluated that stability is overestimated to some degree by the Matsuo-Kawamura method. According to the result by the Tominaga-Hashimoto method there is some risk of sudden failure. This implies that the careful attention is necessary for the management of monitoring the field data. Even though the stability tends to be underestimated by the Kurihara's method, however, it is estimated that this method is applicable to the field when the probable uncertainty at site is considered. For the Shibata-Sekiguchi's method, there is some difficulties in determining the failure index for the practical application, it is considered as safe when the existing estimated failure index is greater than ${\Delta}_q/{\Delta}{\delta}$. In this study, however, it is evaluated to be safe as well when ${\Delta}_q/{\Delta}{\delta}$ to load shows the tendency of constant increase.

• Journal of Distribution Science
• /
• v.12 no.4
• /
• pp.31-39
• /
• 2014

Purpose - This study investigates the following two issues. First, we attempt to find the important determinants of housing investment and to identify their significance rank using survey panel data. Recently, the expansion of global uncertainty in the real estate market has directly and indirectly influenced the Korean housing market; households demonstrate a sensitive reaction to changes in that market. Therefore, this study aims to draw conclusions from understanding how the impact of financial strength of the household is related to house investment. Second, we attempt to verify the effectiveness of diverse indices of financial strength such as DTI, LTV, and PIR as measures to monitor the housing market. In the continuous housing market recession after the global crisis, the government places top priority on residence stability. However, the government still imposes forceful restraints on indices of financial strength. We believe this study verifies the utility of these regulations when used in the housing market. Research design, data, and methodology - The data source for this study is the "National Survey of Tax and Benefit" from 2007 (1st) to 2011 (5th) by the Korea Institute of Public Finance. Based on this survey data, we use panel data of 3,838 households that have been surveyed continuously for 5 years. We sort the base variables according to relevance of house investment criteria using the decision tree model (DTM), which is the standard decision-making model for data-mining techniques. The DTM method is known as a powerful methodology to identify contributory variables for predictive power. In addition, we analyze how important explanatory variables and the financial strength index of households affect housing investment with the binary logistic multi-regressive model. Based on the analyses, we conclude that the financial strength index has a significant role in house investment demand. Results - The results of this research are as follows: 1) The determinants of housing investment are age, consumption expenditures, income, total assets, rent deposit, housing price, habits satisfaction, housing scale, number of household members, and debt related to housing. 2) The impact power of these determinants has changed more or less annually due to economic situations and housing market conditions. The level of consumption expenditure and income are the main determinants before 2009; however, the determinants of housing investment changed to indices of the financial strength of households, i.e., DTI, LTV, and PIR, after 2009. 3) Most of all, since 2009, housing loans has been a more important variable than the level of consumption in making housing market decisions. Conclusions - The results of this research show that sound financing of households has a stronger effect on housing investment than reduced consumption expenditures. At the same time, the key indices that must be monitored by the government under economic emergency conditions differ from those requiring monitoring under normal market conditions; therefore, political indices to encourage and promote the housing market must be divided based on market conditions.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.12
• /
• pp.55-64
• /
• 2016

In this paper bearing capacity and safety margin of shallow foundation on weathered soil ground against shear failure by using current design method of allowable stress design (ASD), load resistance factor design (LRFD) based on reliability analysis and partial safety factor design (PSFD) in Eurocode were estimated and compared to each other. Results of the plate loading test used in construction and design were collected and analysis of probability statistics on soil parameters affecting the bearing capacity of shallow foundation was performed to quantify the uncertainty of them and to investigate the resistance bias factor and covalence of ultimate bearing capacity. For the typical sections of shallow foundation in domestic field as examples, reliability index was obtained by reliability analysis (FORM) and the sensitivity analysis on soil parameters of probability variables was performed to investigate the effect of probability variable on shear failure. From stability analysis for these sections by ASD, LRFD with the target reiability index corresponding to the safety factor used in ASD and PSDF, safety margins were estimated respectively and compared.

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

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.14 no.6
• /
• pp.1-13
• /
• 2015

Travellers consider extra travel time to be arriving their destination because of uncertainty of travel. So it is important to make predictable highway by providing information of travel time variability to traveller so as to enhance level of service at highway. In order to make predictable highway, it is necessary to develope measures of travel time variability that travellers can easily understand. Recently advanced country including the United States, travel time variability index are actively studied. In earlier study, 95percentile of travel time is considered to be most important calculation index of travel time variability. In this study, is has focused on the propriety analysis of 95percentile of travel time in domestic transportation environment. Result of analysis, All of measures(80percentile of travel time, 90percentile of travel time, 95percentile of travel time) show the tendency to increase when case of weather factor occur compare to normal condition under LOS A~D. Especially 95percentile of travel time increased sensitively.