• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.355-365
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• 2014

Concrete-filled tubes (CFTs) have been used in civil engineering practices as a column of buildings and a bridge pier. CFTs have several advantages over the conventional reinforced concrete columns, such as rapid construction, enhanced buckling resistance, and inherited confinement effect. However, CFT component have not been widely used in civil engineering practice, since the design provisions among codes significantly vary each other. It leads to conservative design of CFT component. In this study, the design provisions of AISC and EC4 for CFT component were examined, based on the extensive test results conducted by previous researchers and finite element analysis results obtained in this study. Especially, the focus was made on the validation of P-M interaction curves proposed by AISC and EC4. From the results, it was found that the current design codes considerably underestimated the strength of CFT component under general combined axial load and bending. Finally, the modified P-M interaction curve was proposed and successfully verified.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.257-260
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• 2008

This study will make P-M interaction diagram of residual capacity at fire-damaged High strength concrete column with polypropylene fiber. Evaluating capacity of column decreasing spalling with P-M interaction diagram is important. because high strength concrete column with polypropylene fiber isn't section area loss. P-M interaction diagram that is made to analyze according to a various parameters is useful index for design and evaluating capacity of columns. In this study, spalling, temperature distribution of interior column, residual strength and movement of column in eccentric loading are studied with expose time of high temperature. For study fire test that is similar real act, and after cooling in normal condition residual strength of specimen is estimated. And this study use DIANA(Displacement Analyzer) for analyzing nonlinear analysis. with experiment temperature and strength data.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.575-585
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• 2007

In this study, a new design equation was presented for square CFTs with high-strength concrete subjected to axial compression and bending. In a previous study, a design equation for square CFTs with normal strength concrete was proposed. A parametric study by fiber analysis was performed taking the width-to-thickness ratio (b/t) and the relative concrete strength to the yield strength of the steel tube (fck/Fy) as the main parameters of this study to determine the maximum moment and the axial load at the maximum moment. A new constitutive model for concrete was adopted for fiber analysis in order to take into account the effect of high-strength concrete. The results of the parametric study were embedded into the method which was presented in the previous study to formulate a new design equation that can be easily used for estimating the strength of square CFTs with high-strength concrete.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.335-344
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• 2007

The steel-concrete composite column (i.e., the SC composite column) supports large-gravity loads and simplifies the installation and removal of the work in pouring the concrete. The column takes advantage of the in-plant prefabrication of steel, the speed of erection of a steel structure, and the fire resistance of steel. This paper presents the results of a parametric study using heat transfer analysis and a P-M interaction curve, and compares these results with the experimental results to check the accuracy of the proposed parametric studies. The parametric studies, such as the study of the concrete ratio of an area and the fire protection thickness, provide information on the fire resistance of SC composite columns.

• Journal of Soil and Groundwater Environment
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• v.12 no.6
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• pp.53-59
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• 2007

Optimal quenching curves have been studied for the accurate analysis of $^{14}C$ in groundwater polluted by reducing efficiency of volatile organic compounds (VOCs) in liquid scintillation counter (LSC). The quenching parameters (SQP(E)) were measured for ten VOCs such as benzene, toluene, ethylbenzene, o-(m-,p-)xylene, trichloroethylene (TCE), tetrachloroethylene(PCE), carbon tetrachloride and chloroform. The quenching curves were plotted using $^{14}C$ standard solution and chloroform as a quenching agent. Optimal plotting conditions were determined for standard solution, LSC measuring time and the concentration of chloroform. The quenching effects of chlorinated organic compounds such as TCE, PCE, carbon tetrachloride and chloroform were greater than those of BTEX (benzene, toluene, ethylbenzene and xylene). Optimum measuring time was 100 minutes far 7,000 dpm/mL standard solution. A few mL of chloroform should be added for good quenching curves. These quenching curves have good correlation coefficients (> 0.99) and the curves could be applied to accurate analysis of $^{14}C$ in groundwater and tap water.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.351-360
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• 2009

This study is a series of experimental investigations of the buckling strengths of eccentrically compressed, cold-formed, stainless-steel, circular, hollow-section beam columns. The principal parameters that were used in this study were the slenderness ratios (Lk/r = 30, 50, 70) and the magnitude of eccentricity e(one way: 0, 25, 50, 75, and 100mm: the other way: 0, 12.5, 25, 37.5, and 50mm) on the asymmetrical end-moment of a double curvature. The objectives of the study were to obtain the maximum loads through an experiment and to compare the experimental behaviors with the analysis results. The ultimate buckling strength of the square section members were evaluated using a numerical method, in accordance with the bending moment-axial force(M-P) interaction curves. The behavior of each specimen was displayed in the form of the strength-displacement and moment-angle(M-$\theta$) relationship.

• Tuberculosis and Respiratory Diseases
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• v.39 no.3
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• pp.242-247
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• 1992

Background: The ability to precisely measure specific mRNA levels by hybridization to complementary DNA probes is an important tool for analyzing the regulation of gene expression. Surfactant proteins have important roles in regulating surfactant metabolism as well as in determing its physical properties. Method: The complete coding regions for rat surfactant protein complementary DNA of surfactant protein B were subcloned into pGem 3Z or 4Z such that either antisense or sense transcripts were obtained by using SP 6 RNA polymerase. Surfactant protein B mRNA was measured by filter hybridization. Results: Equation of standard curve between counts per minute (Y) and surfactant protein B mRNA transcript input (X) was Y=2034.9 X+159.1. Correlation coefficient was 1.0. Couclusions: Filter hybridization assay is suited to situation when rapid, accurate quantitation of multiple samples is required.

• Clinical and Experimental Pediatrics
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• v.48 no.12
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• pp.1362-1369
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• 2005

Purpose : This study aimed to investigate the correlation between the plasma level of N-terminal pro-B-type natriuretic peptide(pro-BNP) and several known risk factors influencing outcomes after Fontan operations, and to assess whether pro-BNP levels can be used as predictive risk factors in Fontan operations. Methods : Plasma pro-BNP concentrations were measured in 35 patients with complex cardiac anomalies before catheterization. Cardiac catheterization was performed in all subjects. Mean right atrium pressure, mean pulmonary artery pressure(PAP), and ventricular end-diastolic pressure(EDP) were obtained. Cardiac output and pulmonary vascular resistance were calculated by Fick method. Results : Plasma pro-BNP levels exhibited statistically significant positive correlations with mean PAP(r=0.70, P<0.001), pulmonary vascular resistance(r=0.57, P<0.001), RVEDP(r=0.63, P<0.001), LVEDP(r=0.74, P<0.001), and cardiothoracic ratio(r=0.71, P<0.001). The area under the ROC curve using pro-BNP level to differentiate risk groups in Fontan operations was high : 0.868(95 percent CI, 0.712-1.023, P<0.01). The cutoff value of pro-BNP concentrations for the detection of risk groups in Fontan operations was determined to be 332.4 pg/mL(sensitivity 83.3 percent, specificity 82.7 percent). Conclusion : These data suggest that plasma pro-BNP levels may be used as a predictive risk factor in Fontan operations, and as a guide to determine the mode of therapy during follow-up after Fontan operations.

• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.135-142
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• 1998

본 연구는 초유동 콘크리트용 모르타르의 물/결합재비 및 고성능 감수제 첨가율에 따른 상대플로우 면적비와 상대깔대기 속도비의 상관관계를 실험으로 검토한 것이다. 구속수비 실험결과, C급 플라이애쉬>F급 플라이애쉬 > 석회석분순으로 나타났기 때문에 F급 플라이애쉬 및 석회석분은 유동성 개선에 효과적인 것으로 나타났다. 또한 모르타르 실험결과, 상대플로우 면적비와 상대깔대기 속도비는 고성능 감수제 첨가율이 일정할 경우 물/결합재비의 변화에 따라 원점을 지나는 직선관계로 나타났지만, 물/결합재비가 일정할 경우에는 고성능 감수제 첨가율의 변화에 따라 원점을 지나는 곡선관계로 나타났다. 따라서, 수식화 모델은 Rm= A. m0.4가 합리적이며, 최적값인 ( m .Rm)=(5.1)을 만족하는 배합조건은 플라이애쉬의 경우 치환율 30%, 물/결합재비 83%이며, 석회분의 경우 치환율30%, 물/결합재비 77%로 판명되었다.

• The Korean Journal of Nuclear Medicine
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• v.39 no.4
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• pp.257-262
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• 2005

Purpose: Gastric emptying scan (GES) is usually acquired up to 2 hours. Our study investigated whether a fraction of meal-retention in the stomach at 120 minutes (FR120) was predicted from the data measured for 90 minutes by using non-linear curve fitting. We aimed at saving the delayed imaging by utilizing mathematical models. Materials and Methods: Ninety-six patients underwent GES immediately after taking a boiled egg with 74 MBq (2 mCi) Tc-99m DTPA. The patients were divided into Group I ($T_{1/2}\;{\leq}90\;min$) and Group II ($90\;min). Group I (n=51) had 21 men and 30 women, and Group II (n=45) 15 men and 30 women. There was no significant difference in age and sex between the two groups. Simple exponential, power exponential, and modified power exponential curves were acquired from the measured fraction of meal-retention at each time (0, 15, 30, 45, 60, 75, and 90 min) by non-linear curve fitting ($MATLAB^{\circledR}$ 5.3) and another simple exponential fitting was performed on the fractions at late times (60, 75, and 90 min). A predicted FR120 was calculated from the acquired functional formulas. A correlation coefficient between the measured FR120 and the predicted FR120 was computed ($MedCalc^{\circledR}$ 6.0). Results: Correlation coefficients(r) between the measured FR120 and the predicted FR120 of each mathematical functions were as follows: simple exponential function (Group I: 0.8558, Group II: 0.5982, p<0.0001), power exponential function (Group I: 0.8755, Group II: 0.6008, p<0.0001), modified power exponential function (Group I: 0.8892, Group II: 0.5882, p<0.0001), and simple exponential function at the late times(Group I: 0.9085, Group II: 0.6832, p<0.0001). In all the fitting models, the predicted FR120 were significantly correlated with the measured FR120 in Group I but not in Group II. There was no statistically significant difference in correlation among the 4 mathematical models. Conclusion: In the cases with $T_{1/2}\;{\leq}90\;min$, the predicted FR120 is significantly correlated with the measured FR120. Therefore, FR120 can be predicted from the data measured for 90 minutes by using non-linear curve fitting, saving the delayed imaging after 90 minutes when $T_{1/2}\;{\leq}90\;min$ is ascertained.