• Journal of Environmental Health Sciences
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• v.41 no.5
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• pp.289-298
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• 2015

Objectives: The method of analyzing urinary arsenic by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) is generally used because it shows relatively greater sensitivity, low detection limits, low blocking action, and is simple to operate. In this study, the results of analysis according to three pre-reductants commonly used in the FI-HG-AAS method were compared with each other. Methods: To analyze urinary arsenic, nineteen urine samples were collected from adults aged 43-79 years old without occupational arsenic exposure. Analysis equipment was FI-HG-AAS (AAnalyst 800/FIAS 400, Perkin- Elmer Inc., USA). The three pre-reductants were potassium iodide (KI/AA), C3H7NO2S (L-cysteine), and a mixture of KI/AA and L-cysteine (KI/AA&L-cysteine). Results: In the results of the analysis, the recovery rate of the method using KI/AA was 82.3%, 95.7% for Lcysteine, and 123.5% for KI/AA and L-cysteine combined. When compared with the results by use of high performance liquid chromatography inductively-coupled plasma mass spectrometry (HPLC-ICP-MS), the method using L-cysteine was the closest to those using HPLC-ICP-MS ($98.57{\mu}g/L$ for HPLC-ICP-MS; $74.96{\mu}g/L$ for L-cysteine; $69.23{\mu}g/L$ for KI/AA and L-cysteine; $13.06{\mu}g/L$ for KI/AA) and were significantly correlated (R2=0.882). In addition, they showed the lowest coefficient of variation in the results between two laboratories that applied the same method. Conclusion: The efficiency of hydride generation is considered highly important to the analysis of urinary arsenic via FI-HG-AAS. This study suggests that using L-cysteine as a pre-reductant may be suitable and the most rational among the FI-Hg-AAS methods using pre-reductants.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.373-376
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• 2008

Ultra High Strength Concrete(UHSC) is necessary a clear presentation about mechanical property that is different from normal strength concrete and an evaluation of serviceability of high rise building which is used ultra high strength concrete. To mixing ultra high strength concrete with $f_{ck}$=150MPa pre-mix cement were manufactured and experimental study were conducted to evaluated on the mixing properties and compressive strength with major variables as unit cement contents, water-binder ratio and type of pre-mix cement. As a test result, it is shown that the concrete mixing time is required about 5$^{\sim}$6 minute untill the each materials(ordinary portland cement, silica fume, blast-furnace slag powder and anhydrite) are revitalized enough. A slump flow of fresh concrete are shown about 700$^{\sim}$750mm with proper viscosity. And average value of concrete compressive strength are shown about 77% in 7days, 87% in 14days and 102% in 56days for 28days of concrete material age. From this experimental study, a proper mixture proportion of pre-mix cement are recommended about 54$^{\sim}$59% OPC, 25$^{\sim}$30% blast-furnace slag powder and 10$^{\sim}$15% silica fume for mix the ultra high strength concrete with $f_{ck}$=150MPa.

• Journal of the Korean Geotechnical Society
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• v.36 no.9
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• pp.33-44
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• 2020

In order to analyze the shear strength characteristics of the grout with sudden gelation in the pre-hardening state, the viscosity of the mixture and the indoor vane shear test were performed. The grout was prepared according to the water-cement (w/c) ratio and the shear strength test was conducted. The plastic-state shear strength of grout was affected by the w/c ratio, so the lower the w/c ratio, the higher the initial shear strength was, and the longer the curing time was, the higher the shear strength was. The maximum shear strength occurred at the faster rotation angle as the higher shear strength was developed, and the lower shear strength occurred at the larger rotation angle. In addition, it was confirmed that the pre-hardening grout rapidly decreased in strength after the maximum shear strength was gained, and converged at a certain level after the rotation angle of the vane blade was about 70° to 90°.

• Resources Recycling
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• v.31 no.6
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• pp.44-51
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• 2022

In the steelmaking process using an electric arc furnace (EAF), light-burnt dolomite, which is a flux containing MgO, is used to protect refractory materials and improve desulfurization ability. Furthermore, a recarburizing agent is added to reduce energy consumption via slag foaming and to induce the deoxidation effect. Herein, a waste MgO-C based refractory material was used to achieve the aforementioned effects economically. The waste MgO-C refractory materials contain a significant amount of MgO and graphite components; however, most of these materials are currently discarded instead of being recycled. The mass recycling of waste MgO-C refractory materials would be achievable if their applicability as a flux for steelmaking is proven. Therefore, experiments were performed using a target composition range similar to the commercial EAF slag composition. A pre-melted base slag was prepared by mixing SiO₂, Al₂O₃, and FeO in an alumina crucible and heating at 1450℃ for 1 h or more. Subsequently, a mixed flux #2 (a mixture of light-burnt dolomite, waste MgO-C based refractory material, and limestone) was added to the prepared pre-melted base slag and a melting reaction test was performed. Injecting the pre-melted base slag with the flux facilitates the formation of the target EAF slag. These results were compared with that of mixed flux #1 (a mixture of light-burnt dolomite and limestone), which is a conventional steelmaking flux, and the possibility of replacement was evaluated. To obtain a reliable evaluation, characterization techniques like X-ray diffraction (XRD) analysis and X-ray fluorescence (XRF) spectrometry were used, and slag foam height, slag basicity, and Fe recovery were calculated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.21-27
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• 2016

Global warming due to greenhouse gas emissions is considered as a major problem worldwide, and many countries are making great efforts to reduce carbon dioxide emissions. Many technologies in post-combustion, pre-combustion and oxy-fuel combustion $CO_2$ capture have been developed. Among them, a hybrid pre-combustion $CO_2$ capture system of a water gas shift (WGS) reactor and a membrane gas separation unit was investigated. The 2 stage WGS reactor integrated high temperature shift (HTS) with a low temperature shift (LTS) was used to obtain a higher CO conversion rate. A Pd/Cu dense metal membrane was used to separate $H_2$ from $CO_2$ selectively. The performance of the hybrid system in terms of CO conversion and $H_2$ separation was evaluated using a 65% CO, 30 % $H_2$ and 5% $CO_2$ gas mixture for applications to pre-combustion $CO_2$ capture. The experiments were carried out over the range of WGS temperatures ($200-400^{\circ}C$), WGS pressures (0-20bar), Steam/Carbon (S/C) ratios (2.5-5) in a feed gas flow rate of 1 L/min. A very high CO conversion rate of 99.5% was achieved with the HTS-LTS 2 stage water gas shift reactor, and 83% $CO_2$ was concentrated in the retentate using the Pd/Cu membrane.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.99-100
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• 2008

This paper proposes a Gaussian Mixture Model (GMM) - based speech emotion recognition methods using four feature parameters; 1) Fast Fourier Transform(FFT) spectral entropy, 2) delta FFT spectral entropy, 3) Mel-frequency Filter Bank (MFB) spectral entropy, and 4) delta MFB spectral entropy. In addition, we use four emotions in a speech database including anger, sadness, happiness, and neutrality. We perform speech emotion recognition experiments using each pre-defined emotion and gender. The experimental results show that the proposed emotion recognition using FFT spectral-based entropy and MFB spectral-based entropy performs better than existing emotion recognition based on GMM using energy, Zero Crossing Rate (ZCR), Linear Prediction Coefficient (LPC), and pitch parameters. In experimental Results, we attained a maximum recognition rate of 75.1% when we used MFB spectral entropy and delta MFB spectral entropy.

• Fibers and Polymers
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• v.6 no.3
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• pp.229-234
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• 2005

In this paper, chitosan was suggested for using as a replacement for sodium alginate in the pretreatment print paste for digital ink-jet printing for cotton fabric. Pretreatment print pastes prepared from the mixture of chitosan and acetic acid with the appropriate viscosity gave satisfactory prints on the cotton fabric. Chitosan-treated cotton fabrics were digitally ink-jet printed with four different colors and the color fastness rating of the printed fabrics was satisfactory. Experimental results revealed the possibility of pre-treating the cotton with chitosan to replace the sodium alginate normally present in the pretreatment print paste recipe.

• Textile Coloration and Finishing
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• v.10 no.6
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• pp.55-66
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• 1998

In order to investigate the detergency effects of various detergents to stained polyester & cotton fabric with solid soils such as carbon black, liquid paraffin and fat, the optimum washing conditions according to the types of washing agent, the assesment of detergency effect by the measurement of reflectance after and before washing were studied. The detergency effect of various detergents to stained polyester and cotton fabric increased by using the mixtures of bleaching and enzyme detergent. In order to obtain the excellent detergency effect, 2-step treatment, the pre-washing with bleaching agent and bleaching-enzyme mixture detergent treatment is preferred. In comparison of the detergency to polyester and cotton fabric, it is assumed that the detergency to polyester stained fabric was superior than that to cotton stained fabric because of the difference of adhesive force between soil material and fabric in preparing solid stained fabric.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.147-157
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• 1996

Natural gas is gaining more attraction as a future fuel in particular both for environmental protection and energy conservation. In order to bring about more widespread use of gaseous engines, the technology capable of achieving output and efficiency performance equivalent to that of diesel engines needs to be developed. In the present paper, the requirements of the pilot torch from pre-chamber for ensuring ignition and promoting combustion are discussed by means of taking high-speed flame photography and system can run with leaner mixture of various fuels comparing to the electric plug ignition system cause the ignition delay period ignited with the torch and the combustion period are very short in spite of changing A/F of gaseous fuels in the main chamber. However, the suitable piston-cavity design for the use of lower-hydrocarbon fuels such as propane and butane must be discussed increasingly in the mear future.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.121-130
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• 1999

It is necessary to measure pressure, temperature, chemical equilibrium and the shape of flame in order to understand the combustion process in a combustion chamber. In particular, the flame formulation and combustion process of divided combustion chamber are different from those of a single chamber, And the variable diameter of a jet hole can effect not only physical properties like ejection velocity, temperature and time of combustion but also a chemical property like the reaction mechanism. Accordingly temperature is one of the most important factors which influence the combustion mechanism. This paper observed shape of flame by using the schlieren photographs and measured the pressure in a combustion chamber and the reaching time of the flame by ion probe By doing these, we investigation the formulation of the flame and the process of propagation. These measurement methods can be advanced in understanding the combustion process and process and propagation of flame.