• Analytical Science and Technology
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• v.25 no.5
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• pp.265-272
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• 2012

Okamoto cavity was modified to generate high power (2.45 GHz, 2 kW) He, N2 and Ar plasmas with WR-340 waveguide. Many factors which influence to the plasma generation were optimized and investigated for the spectroscopic properties of the He plasma generated. Some of the important factors are the diameter of the inner conductor, the distance between the inner and outer conductors and the distance between the tip of the inner conductor and the torch. After optimization for the He, two torches (a commercial mini torch for ICP and a tangential flow torch made locally) were compared and showed similar results for the helium plasma gas flow of 25 L/min~30 L/min. A tall torch (extended) was used to block the air in-flow and reduced the background intensity at 340 nm region (NH band). Emission intensity was measured for determination of halogen element in the aqueous solution with power and carrier gas flow rate. Electron number density and the excitation temperature were on the order of $3.67{\times}10^{11}/cm^3$ and 4,350 K, respectively. These values are similar or a bit smaller than other microwave plasmas. It has been possible to analyze aqueous samples. The detection limit for Cl (479.45 nm) was obtained to be 116 mg/L and needs analytical optimization for the better performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.113-125
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• 2017

In spite of bulk literature about the tuning of TMD, the effectiveness of TMD in reducing the seismic response of engineering structures is still in a row. This paper deals with the optimum tuning parameters of a passive TMD and simulated on MATLAB with a ten-story numerical shear building. A weighted multi-objective optimization method based on computer experiment consisting of coupled with central composite design(CCD) central composite design and response surface methodology(RSM) was applied to find out the optimum tuning parameters of TMD. After the optimization, the so-conceived TMD turns out to be optimal with respect to the specific seismic event, hence allowing for an optimum reduction in seismic response. The method was employed on above structure by assuming first the El Centro seismic input as a sort of benchmark excitation, and then additional recent strong-motion earthquakes. It is found that the RSM based weighted multi-objective optimized damper improves frequency responses and root mean square displacements of the structure without TMD by 31.6% and 82.3% under El Centro earthquake, respectively, and has an equal or higher performance than the conventionally designed dampers with respect to frequency responses and root mean square displacements and when applied to earthquakes.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.1-9
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• 2010

Most of shear wall structures require openings in shear walls and thus shear walls are linked by floor slabs or coupling beams resulting in the coupled shear wall structures. When these structures are subjected to seismic excitations, excessive shear forces are induced in coupling beams. Accordingly, brittle failure of coupling beams may occur or shear walls may yield first. To avoid this problem, damping devices can be installed in coupling beams. It can increase the vibration control effect and improve the seismic resistance performance of the coupled shear wall structure by avoiding stress concentration and the brittle failure of coupling beams. Based on this background research, an LRB (lead rubber bearing) was introduced in the middle of the coupling beam in this study and the authors investigated the seismic response control effect and stress distribution of the proposed system. To this end, a modeling technique that can effectively predict the structural behavior of coupled shear wall structures has been proposed. With this proposed technique, time history analyses of the example coupled shear wall structure subjected to seismic excitation were performed and the vibration control effects of the seismic responses were investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.323-330
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• 2012

This study deals with the experiments of liquid dampers with multi cells whose vertical tubes are divided into several square columns for easily changing natural frequencies. Shaking table test is performed to verify control effectiveness of the dampers which are installed on a building structure. To design liquid dampers, a 64-story building structure is reduced to a SDOF structure with 1/20 of similitude laws based on acceleration. The structure model is made up to adjust its mass and stiffness easily, with separate mass and drive parts. Mass parts indicate real structure's weights and drive parts indicate real structure's stiffness with springs and LM guides. Manufactured liquid damper has 18 cells and its natural frequency ranges are 0.65Hz to 0.81Hz. Shaking table test is carried out with one way excitation to compare with only accelerations of a large-scale structure and a structure installed with liquid dampers. Control performance of the liquid damper is expressed by the transfer function from shaking table accelerations to the large-scale structure ones. Testing results show that the liquid damper reduced a large-scale structure's response by tuned natural frequencies.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.132-138
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• 2003

The use of long rails in high-speed railway bridges causes additional stresses due to nonlinear behaviours between the rail and bridge decks in the neighbourhood of the deck joints. In the seismic response analysis of high-speed railway bridges, since structural response is highly sensitive to properties of the ground motion, spatial variation of the ground excitation affects responses of the bridges, which in turn affect stresses in the rails. In addition, it is shown that high-speed trains need very long distances to stop when braking under seismic occurrence corresponding to operational earthquake performance level so that verification of the safe stoppage of the train is also required. In view of such additional stresses due to long rails, sensibility of structural response to the properties of the ground motion and braking distance needed by the train to stop safely, this paper proposes and establishes a time domain nonlinear dynamic analysis method that accounts for braking loads, spatial variation of the ground motion and material nonlinearities of rails to analyze long rail stresses in high-speed railway bridges subjected to seismic event. The accuracy of the proposed method is demonstrated through an application on a typical site of the Korean high-speed railway.

• Journal of Preventive Medicine and Public Health
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• v.35 no.4
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• pp.282-286
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• 2002

Objectives : The level of 4-hydroxyproline (4-Hyp) in human urine was measured using high performance liquid chromatography (HPLC) with a fluorescence detector. This method is useful for medical examinations and investigating the radicals induced by physical, chemical, mental stresses. This method is superior to many published several methods in terms of its low cost and ability to analyze many samples. Methods : The urine from workers in a tire manufacturing company (22 male pre- and post-shift workers) and 18 office-workers as controls were analyzed. Data concerning age, the cumulative drinking amount and the cumulative smoking amount was collected with a questionnaire. The optimum applied amount of dansyl-Cl, the optimum reaction temperature and time, the recoveries and the optimum pH of the eluent and buffer were determined.4-Hyp from human urine was derivatized with dansyl-Cl (dimethylamino-naphthalene-1-sulfonyl chloride) after removing the a-amino acid by a treatment with phthalic dicarboxaldehyde (OPA) and cleaned with Bond Elut C18 column. The 4-Hyp derivatives were separated on a reversed phase column by gradient elution with a phosphate buffer (5 mmol, pH 8.0) and acetonitrile, and detected by fluorescence measurements at 340 nm (excitation) and 538 nm (emission). Results : The detection limit for the urinary free 4-Hyp was $0.364{\mu}mol/l$. The recovery rate of 4-Hyp was 99.7%, and the effective pH of the phosphate buffer and borate buffer were 3.0 and 8.0, respectively. From statistical analysis, age, drinking and smoking did not affect the urinary free 4-Hyp in both the controls and workers. The range of urinary 4-Hyp in the controls, pre-shift, and post-shift workers were 0.33-16.44, N.D-49.06, and $0.32-56.27{\mu}mol/l$. From the pared-sample t-test, the urinary 4-Hyp levels in post-shift workers ($11.82{\pm}6.73\;nmmol/mg\;Cre$) were 2-fold higher than in pre-shift workers ($5.36{\pm}5.53\;nmol;/mg\;Cre$) and controls ($4.91{\pm}4.89\;nmol;/mg\;Cre$). Conclusions : This method was developed with high sensitivity, accuracy, and precision. The present method was effectively applied to analyze the urinary free 4-Hyp in both controls and workers.