• Journal of Korean Society of Steel Construction
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• 제23권6호
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• pp.747-761
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• 2011

This paper presents an investigation on the change in the statical behavior and the ultimate capacity of steel cable-stayed bridges after cable failure. Cable failure can occur due to fire, direct vehicle clash accidents, cable or anchorage fatigue, and so on. Moreover, the cable may be temporarily disconnected during cable replacement work. When cable failure occurs, the load, that was supported by the broken cable is first transferred to another cable. Then the structural state changes due to the interaction between the girder, mast, and cables. Moreover, it can be predicted that the ultimate capacity will decrease after cable failure, because of the loss of the support system. In this study, the analysis method is suggested to find the new equilibrium state after cable failure based on the theory of nonlinear finite element analysis. Moreover, the ultimate analysis method is also suggested to analyze the ultimate behavior of live loads after cable failure. For a more rational analysis, a three-step analysis procedure is suggested and used, which consisted of initial shape analysis, cable failure analysis, and live load analysis. Using this analysis method, an analytical study was performed to investigate the changes in the structural state and ultimate behavior of steel cable-stayed bridges.

• Journal of Korean Society of Steel Construction
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• 제14권4호
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• pp.557-566
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• 2002

This paper summarized the results of a full-scale cyclic seismic testing on four reduced beam section (RBS) steel moment connections. Specifically, these tests addressed a bolted web versus a welded web connection and strong versus medium panel zone (PZ) strength as key test variables. Specimens with medium PZ strength were designed to promote balanced energy dissipation from both PZ and RBS regions, in order to reduce the requirement for expensive doubler plates. Both strong and medium PZ specimens with welded web connection were able to provide sufficient connection rotation capacity required of special moment-resisting frames. On the other hand, specimens with bolted web connection performed poorly due to premature brittle fracture of the beam flange at the weld access hole. Unlike the case of web-welded specimens, specimens with cheaper bolted web connection could not transfer the actual plastic moment of the original (or unreduced) beam section to the column. No fracture occurred within the beam groove welds of any connection in this testing program. If fracture within the beam flange groove weld is avoided by using quality welding procedure as in this study, the fracture issue tends to move into the beam flange base metal at the weld access hole. Supporting analytical study was also conducted in order to understand the observed base metal fracture from the engineering mechanics perspective.

• Journal of Korean Society of Transportation
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• 제21권2호
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• pp.107-118
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• 2003

Highway Capacity Manual (HCM) provides an analytical delay estimation model to assist the evaluation of traffic at a signalized intersection. The model revised and included in the HCM published in the year 2000 reflects the results of recent studies and is utilized in various fields of transportation studies. For the implementation of the model in the case of permitted left turns, the HCM supplement provides a computational procedure to adjust the saturation flow rate of permitted left toms. The model however, is originally designed for a protected movement and thus underestimates the delay of permitted left turns due to its difference right-of-way nature. This document describes (1) a review of the theoretical background of the HCM delay estimation model, (2) problems embedded in the model for the delay estimation of permitted left turns, (3) a proposed model developed in this study to improve the delay estimation for permitted left turns and (4) a set of verification tests. In order to reflect various traffic and control conditions in the test, simulation studies were performed to by using the field data based on 120 different permitted left-turn scenarios. Comparison studies conducted between sets of delays estimated by the HCM and the proposed models against a set of the CORSIM delays and showed that the proposed model improved the estimation of the permitted left-turn delays. The explanatory variable of the relationship between the HCM delay and the simulation delay was 0.47 and the one between the delay estimated by the proposed model and the simulation delay was 0.77.

• Biomolecules & Therapeutics
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• 제9권4호
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• pp.291-297
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• 2001

The bioequivalence of two triflusal products was evaluated with 20 healthy volunteers following single oral dose according to the guidelines of Korea Food and Drug Administration (KFDA). Trisa $l^{R}$ capsule (Whanin Pharm. Corp., Korea) and Disgre $n^{R}$ capsule (Myung-In Pharm. Corp., Korea) were used as test product and reference product, respectively. Both products contain 300 mg of trifusal. One capsule of test product or reference product was orally administered to the volunteers, respectively, by randomized two period crossover study (2$\times$2 Latin square method). Blood samples were taken at predetermined time intervals for 4 hours and the determination of trifusal was accomplished using semi-microbore HPLC equipped with automated column switching system. The analytical method with HPLC was validated according to the Bioanalytic Method Validation guideline by F7A prior to determining the plasma samples. The pharmacokinetic parameters (AU $C_{0-4h}$ $C_{max}$ and $T_{max}$) were calculated and ANOVA test was utilized for statistical analysis of parameters. As a result of the assay validation, the limit of quantification of trifusal in human plasma by current assay procedure was 50 ng/ml using 500 $\mu$l of plasma. The accuracy of the assay was from 97.76% to 116.51% while the intra-day and inter-day coefficient of variation of the same concentration range was less than 15%. Average drug concentration at the designated time intervals and pharmacokinetic parameters calculated were not significantly different between two products (p>0.05). The difference of mean AU $C_{olongrightarrow4hr}$, $C_{max}$, and $T_{max}$ between the two products (2.92, 4.39, and -2.44%, respectively) were less than 20%. The power (1-$\beta$) and treatment difference ($\Delta$) for AU $C_{olongrightarrow4hr}$ and $C_{max}$ were more than 0.8 and less than 0.2, respectively. Although the power for $T_{max}$ was under 0.8, $T_{max}$ of the two products was not significantly different from each other (p>0.05). These results satisfied the criteria of KFDA guideline for bioequivalence, indicating the two products of triflusal were bioequivalent.quivalent.ent.ent.

• Korean Journal of Environmental Agriculture
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• 제36권1호
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• pp.63-66
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• 2017

BACKGROUND: The phenol concentrations in water samples were determined using gas chromatography after derivatization of the analyte to phenyl acetate followed by extraction using a large volume of solvent. However, this procedure requires an additional purification step and is not analytically efficient. METHODS AND RESULTS: In this study, phenol was first extracted from an acidified water sample using ethyl acetate and then acetylated using acetic anhydride in the presence of a small amount of water and $K_2CO_3$. The derivative was extracted using 1mL of n-butyl acetate. One microliter of the extract was analyzed by GC-MS without further purification. The calibration curve showed good linearity with the $r^2$ value of 0.9968. The method detection limit and the limit of quantitation were estimated to be $0.18{\mu}g/L$ and $0.56{\mu}g/L$, respectively. Repeatability (RSD, n=3) and recovery (n=3) were 9.1%-4.3% and 90.6%-110.5%, respectively. The concentrations of phenol in a few samples of stream water were distributed in the range of $2.51-7.51{\mu}g/L$. CONCLUSION: This method is simpler and faster to implement than those currently utilized and shows high analytical reliability. It can be applied to the quantitative determination of phenol concentrations in surface water and groundwater samples.

• Journal of Food Hygiene and Safety
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• 제35권4호
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• pp.312-318
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• 2020

A method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for neonicotinoid pesticide analysis in agricultural products. Four compounds (imidacloprid, clothianidin, acetamiprid, thiacloprid) were extracted with acetonitrile from agricultural products and cleaned up by NH₂ solid-phase extraction procedure, and eluted with 0.1% formic acid in methanol/dichloromethane (5/95, v/v). The limit of detection and quantification were 0.0001-0.0005 mg/kg and 0.001 mg/kg, respectively. The mean recoveries of neonicotinoid pesticide from agricultural products were in the range of 90.7-100.9% and 94.4-99.8%, as spiked at 0.2 mg/kg and 0.02 mg/kg, respectively. This validation satisfied the national criteria for pesticide analytical methods. In summary, The present method is fast, precise and sensitive enough for the Positive List System (PLS), and we conclude that the method is also suitable for neonicotinoid pesticide determination in a wide range of agricultural products.

• Journal of Life Science
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• 제14권2호
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• pp.286-290
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• 2004

The antioxidant activities of the various fractions extracted from mustard leaf (Brassica juncea) and mustard leaf kimchi were determined by the radical scavenging effect on 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical. The fractions from dried mustard leaf, and fermented mustard leaf kimchi for 0 day and fermented mustard leaf kimchi for 5 days at 15$^{\circ}C$ were screened for the scavenging effects by using DPPH assay. The fractions prepared by the systematic extraction procedure with the solvents such as hexane, C $H_2$Cl$_2$, EtOAc, BuOH and $H_2O$ were used for the determination of free radical scavenging effects. The antioxidant activity of EtOAc and n-BuOH soluble fraction from mustard leaf and mustard leaf kimchi for 0 day had stronger than the others. During fermentation at 15$^{\circ}C$ for 5 days, the antioxidant activity was changed. C $H_2$Cl$_2$ and EtOAc soluble fraction showed more potent radical scavenger effects than the others. The difference or results were to the various supplements and fermentation process.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제19권4호
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• pp.429-440
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• 2006

This paper comprises two specific objectives. The first is to examine the applicability of ordinary kriging interpolation(OK) to the p-adaptivity of the finite element method that is based on variogram modeling. The second objective Is to present the adaptive procedure by the hierarchical p-refinement in conjunction with a posteriori error estimator using the modified S.P.R. (superconvergent patch recovery) method. The ordinary kriging method that is one of weighted interpolation techniques is applied to obtain the estimated exact solution from the stress data at the Gauss points. The weight factor is determined by experimental and theoretical variograms for interpolation of stress data apart from the conventional interpolation methods that use an equal weight factor. In the p-refinement, the analytical domain has to be refined automatically to obtain an acceptable level of accuracy by increasing the p-level non-uniformly or selectively. To verify the performance of the modified S.P.R. method, the new error estimator based on limit value has been proposed. The validity of the proposed approach has been tested with the help of some benchmark problems of linear elastic fracture mechanics such as a centrally cracked panel, a single edged crack, and a double edged crack.

• Journal of the Korean Society for Advanced Composite Structures
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• 제2권3호
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• pp.1-11
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• 2011

The typical truss-lattice material successively packed by repeated cubic symmetric unit cells consists of sub-elements (SE) proposed in this study. The representative continuum model for this truss-lattice material such as the effective strain and stress relationship can be formulated by the homogenization procedure based on the notation of averaged mechanical properties. The volume fractions of micro-scale struts have a significant influence on the effective strength as well as the relative density in the lattice plate with replicable unit cell structures. Most of the strength contribution in the lattice material is induced by axial stiffness under uniform stretching or compression responses. Therefore, continuum based constitutive models composed of homogenized member stiffness include these mechanical characteristics with respect to strength, internal stress state, material density based on the volume fraction and even failure modes. It can be also recognized that the stress state of micro-scale struts is directly associated with the continuum constitutive model. The plastic flow at the micro-scale stress can extend the envelope of the analytical stress function on the surface of macro-scale stress derived from homogenized constitutive equations. The main focus of this study is to investigate the basic topology of unit cell structures with the cubic symmetric system and to formulate the plastic models to predict pressure dependent macro-scale stress surface functions.

• Korean Journal of Childcare and Education
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• 제3권2호
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• pp.48-67
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• 2007

In the case of students hoping to be a nursery school and kindergarten teacher in future, the educational experience which can not learning in the class work was help to increase their understand for the instruction methods in nursery school sport and them to have a instruction mind as a nurser school teacher by direct and concrete. In the aspects, the observation program on an actual spot is a important plan to be a extend of course work and one of alternation programs in child education. This study was emphasized that the observation program is necessary and useful procedure for students who will be prepared a practical training course for 4 weeks and that help to understand the change of their recognition before the observation and after. Also the analytical work was prepared to use usefully for a teacher aspirants to acquire an effective educational method on the actual teaching class. The result shows that the observation program for practical training on an actual sport would give the practical major knowledge to students in course work of a child education school. The educational program which was consisted with the observation and the training course work on the actual sport would be necessary prepared in a regular curriculum for the most of teacher aspirants This systematically analysis explains that the educational program like an observation on actual sport offer to the student as one of course works and it will be sufficiently prepared for promotion of their understand and experience about the child education.