• Journal of Multimedia Information System
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• v.5 no.4
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• pp.235-244
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• 2018

Potential maximum soil moisture retention (S) is a dominant parameter in the Soil Conservation Service (SCS; now called the USDA Natural Resources Conservation Service (NRCS)) runoff Curve Number (CN) method commonly used in hydrologic modeling for event-based flood forecasting (SCS, 1985). Physically, S represents the depth [L] soil could store water through infiltration. The depth of soil moisture retention will vary depending on infiltration from previous rainfall events; an adjustment is usually made using a factor for Antecedent Moisture Conditions (AMCs). Application of the method for continuous simulation of multiple storms has typically involved updating the AMC and S. However, these studies have focused on a time step where S is allowed to vary at daily or longer time scales. While useful for hydrologic events that span multiple days, this temporal resolution is too coarse for short-term applications such as flash flood events. In this study, an approach for deriving a time-variable potential maximum soil moisture retention curve (S-curve) at hourly time-scales is presented. The methodology is applied to the Napa River basin, California. Rainfall events from 2011 to 2012 are used for estimating the event-based S. As a result, we derive an S-curve which is classified into three sections depending on the recovery rate of S for soil moisture conditions ranging from 1) dry, 2) transitional from dry to wet, and 3) wet. The first section is described as gradually increasing recovering S (0.97 mm/hr or 23.28 mm/day), the second section is described as steeply recovering S (2.11 mm/hr or 50.64 mm/day) and the third section is described as gradually decreasing recovery (0.34 mm/hr or 8.16 mm/day). Using the S-curve, we can estimate the hourly change of soil moisture content according to the time duration after rainfall cessation, which is then used to estimate direct runoff for a continuous simulation for flood forecasting.

• Journal of Embryo Transfer
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• v.15 no.3
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• pp.237-245
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• 2000

This study was carried out to elucidate whether sperm contain a factor inducing second polar body extrusion and to search for an effective collection method of the sperm factor Thus, sperm extract, dialyzed sperm-extract or liquid chromatographic fractions of sperm extract was microinjected into ovulated oocytes. And the microinjected oocytes were incubated for 24 hours to investigate about the extrusion of second polar body. The results obtained were as follows; 1. Sperm extract significantly increased the second polar body extrusion. 2. Sperm extract showed five major fractions at retention volumes (RVs) 1.25, 1.37, 1.84, 2.10 and 2.67ml after separation with Superose 12 column. These sperm extract fractions did not significantly increase the second polar body extrusion. 3. Dialyzed sperm-extract significantly increased the second polar body extrusion 4. Dialyzed sperm-extract showed three maior fractions at RVs 1.88, 2.14 and 2.77ml after separation with Superose 12 column. Of these fractions, the fraction RV2.14 significantly increased the second polar body extrusion. In conclusion, sperm extract contained a factor inducing the second polar body extrusion and the factor was contained largely in fraction RV2.14 after dialysis and liquid chromatographic fractionation of sperm extract.

• Journal of the Korean Chemical Society
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• v.30 no.4
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• pp.352-358
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• 1986

An extensive experimental survey on the retention behaviors of phenols in the binary solvent system such as methanol-water, acetonitrile-water and tetrahydrofuran-water as well as the ternary solvent system such as methanol-acetonitrile-water and methanol-tetrahydrofuran-water is presented. A linear equation, which describes the capacity factor as a function of the solvent composition in the mobile phase and is able to predict the retention behaviors of phenols, was obtained. The iso-eluotropic lines for the binary and ternary solvent system are based on the equal strength of the methanol-water solvent which shows an optimum separation of the phenols used. The specific effect of each solute in the binary solvent system appeared to be larger than those in the ternary system.

• Korean Journal of Labor Studies
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• v.23 no.2
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• pp.169-193
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• 2017

This study analyzed the determinants that affect employment retention rate in order to diagnose dynamic employment stability in Korea. For this analysis, we constructed multi-level hierarchical data linking Workplace panel survey data and employment insurance job history data. And the determinants were analyzed using a multi-level analysis model suitable for these data. As result of the analysis, it is estimated that the employment stability is very low in Korea due to the widespread existence of the marginal sectors with low wage level and high level of nonstandard employment. In addition, the results of this analysis show that employment structure of Korea occupies considerable area of short-term employment where employment and unemployment are repeated, and overall employment stability is weak. This fact is likely to be a limiting factor for continued growth, as there is limited opportunity for skill development and skills formation at the corporate and individual levels. According to the results of this analysis, it is required to improve the quality of the employment structure for continuous growth and skill formation.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1745-1750
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• 2013

A novel green aqueous mobile phase modified with room temperature ionic liquids (RTILs) was employed in the absence of volatile organic solvents or ion-pairing reagents to analyze thiamine, a very polar compound, by reverse phase high performance liquid chromatography (RP-HPLC). Due to its strongly hydrophilic nature, thiamine was eluted near the column dead time ($t_0$) using a mobile phase without adding RTILs or ion-pairing reagents, even if a 100% aqueous mobile phase, which has weak elution power under reverse phase conditions, was used. Thus, 1-ethyl-3-methyl-imidazolium hexafluorophosphate ([EMIM][$PF_6$]), which has the strongest chaotropic effect, was selected as a mobile phase additive to improve retention and avoid baseline disturbances at $t_0$. Various mobile phase parameters such as cation moiety, chaotropic anion moiety, pH and concentration of RTILs were optimized to determine thiamine at the proper retention time. Method validation was performed to assess linearity, intra- and inter-day accuracy and precision, recovery and repeatability; all results were found to be satisfactory. The developed method was also compared to the current official United States Pharmacopoeia (USP) and Korean Pharmacopoeia (KP) methods using an organic mobile phase containing an ionpairing reagent by means of evaluating various chromatographic parameters such as the capacity factor, theoretical plate number, peak asymmetry and tailing factor. The results indicated that the proposed method exhibited better efficiency of thiamine analysis than the official methods, and it was successfully applied to quantify thiamine in pharmaceutical preparations.

• The korean journal of orthodontics
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• v.50 no.6
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• pp.363-372
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• 2020

Objective: To develop a standardized instrument to measure the level of cognition for orthodontic treatment in adults, and verify its reliability and validity for assessing perceptions of orthodontic treatment in adults. Methods: A total of 406 adults aged 19-64 years were surveyed by an internet research system. A tool was developed through the instrument development and verification stages. The data were analyzed by correlation analysis, exploratory factor analysis, confirmatory factor analysis, and Cronbach's α test. Results: The instrument consisted of 11 items covering four factors related to orthodontic treatment. Three items were related to general perception, four described the perception of the treatment for adults, two related to the treatment effects, and two related to the retention of orthodontic treatment. In the reliability test, Cronbach's α was 0.845 for the 11 items. In assessments for individual components, Cronbach's α was 0.764 for the general perception of orthodontic treatment, 0.705 for the perception of this treatment for adults, 0.707 for the effects of the treatment, and 0.701 for the retention of orthodontic treatment. Finally, a measurement instrument for the perception of orthodontic treatment in adults was designed to assess the 11 items on a four-point Likert scale. Conclusions: This study developed a standard measurement instrument for assessing the perception of orthodontic treatment in adults. The proposed instrument will enable additional studies on the influence of an adult's perception of orthodontic treatment on the decision to undergo treatment.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.27 no.2
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• pp.123-129
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• 2017

Objectives: The purpose of this study is to enhance the application of analytical method of polar solvents(alcohols) by GCOTC (gas chromatography open tubular column) through the system suitability test(SST) to estimate the whole chromatographic system performance(integral part). Methods: To perform the SST, carried out repeatability(n=6) as analytical method of polar solvents by GCOTC, got the retention time($t_R$), standard deviation(${\sigma}_{n-1}$) of $t_R$, baseline width($w_b=4{\sigma}_{n-1}$) and calculated dead time($t_m$) by $v_m=d^2{\pi}L(f/4)$ and $v_m=t_m$ x flow rate. Results: In this experiment, obtained the basic data, there were $t_m=2$ min, methanol($t_R=3.569$, ${\sigma}_{n-1}=0.01$, $w_b=0.04$), ethanol ($t_R=3.892$, ${\sigma}_{n-1}=0.004$, $w_b=0.016$), isopropanol($t_R=4.209$, ${\sigma}_{n-1}=0.004$, $w_b=0.016$). By using these data, calculated the corrected retention time($t_R{^{\prime}}$), capacity factor(k), separation factor(${\alpha}$), number of theoretical plate(n) and resolution($R_s$) for SST and got the good results. Conclusions: Through the SST, could reconfirm the whole chromatographic performance system(integral part) for analytical method of polar solvents by GCOTC. Therefore, this analytical method expect to be widely applied at the related areas.

• Journal of Environmental Impact Assessment
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• v.9 no.3
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• pp.203-214
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• 2000

Health risk assessment is applied to streamlining LCA(Life Cycle Assessment) using Monte carlo simulation for probabilistic/stochastic exposure and risk distribution analysis caused by data variability and uncertainty. A case study was carried out to find benefits of this application. BTC(Benzene, Trichloroethylene, Carbon tetrachloride mixture alias) personal exposure cases were assumed as production worker(in workplace), manager(in office) and business man(outdoor). These cases were different from occupational retention time and exposure concentration for BTC consumption pattern. The result of cancer risk in these 3 scenario cases were estimated as $1.72E-4{\pm}1.2E+0$(production worker; case A), $9.62E-5{\pm}1.44E-5$(manger; case B), $6.90E-5{\pm}1.16E+0$(business man; case C), respectively. Portions of over acceptable risk 1.00E-4(assumed standard) were 99.85%, 38.89% and 0.61%, respectively. Estimated BTC risk was log-normal pattern, but some of distributions did not have any formal patterns. Except first impact factor(BTC emission quantity), sensitivity analysis showed that main effective factor was retention time in their occupational exposure sites. This case study is a good example to cover that LCA with probabilistic risk analysis tool can supply various significant information such as statistical distribution including personal/environmental exposure level, daily time activity pattern and individual susceptibility. Further research is needed for investigating real data of these input variables and personal exposure concentration and application of this study methodology.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.113-120
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• 2012

An actual slope failure was analyzed in residual soils at Jinju. Due to rainfall infiltration, the safety factor decreases in the unsaturated layers, since the effective stress and shear strength decrease. In this study, the effective stress is based on suction stress using soil water retention curve. Unsaturated properties were evaluated on soil water retention curve, hydraulic conductivity and shear strength with samples from the site. After infiltration analysis of unsaturated flow under the actual rainfall, the distribution of pore water pressure could be calculated in the slope layers. In the stress field of finite elements, an elastic analysis calculated total stress distribution in the layers and also shear stresses on the slip surface using elastic model. On the slip surface, suction stress and effective stress evaluated the shear strength. As a result, the factor of safety was calculated due to rainfall, which could simulate the actual slope failure. In particular, it was found that the suction stress increases and both the effective stress and the shear strength decrease simultaneously on the slip surface.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1717-1723
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• 2007

In this study , quasi-MFISFET (Metal-Ferroelectric-Insulator-Semiconductor FET) devices are fabricated using PLZT(10/30/70), PLT(10), PZT(30/70) thin film and their drain current properties are investigated. It is found that the drain current of quasi-MFISFET is directly influenced by the polarization strength of ferroelectric thin fan. Also, when the gate voltages are ${\pm}5\;and\;{\pm}10V$, the memory windows are 0.5 and 1.3V, respectively. It means that the memory window is changed with the variation of coercive voltage generated by the voltage applied on ferroelectric thin film. The electric field and the leakage current with time delay of PLZT(10/30/70) thin lam are measured to investigate the retention property of MFISFET device. Some material parameters such as current density constant, $J_{ETO}$, electric field dependent factor K and time dependent factor m are obtained. The variation of charge density with time is quantitatively analyzed by using the material parameters.