• 한국재료학회지
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• 제31권12호
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• pp.704-709
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• 2021

In the flux used in the batch galvanizing process, the effect of the component ratio of NH₄Cl to ZnCl₂ on the microstructure, coating adhesion, and corrosion resistance of Zn-Mg-Al ternary alloy-coated steel is evaluated. Many defects such as cracks and bare spots are formed inside the Zn-Mg-Al coating layer during treatment with the flux composition generally used for Zn coating. Deterioration of the coating property is due to the formation of AlCl_x mixture generated by the reaction of Al element and chloride in the flux. The coatability of the Zn-Mg-Al alloy coating is improved by increasing the content of ZnCl₂ in the flux to reduce the amount of chlorine reacting with Al while maintaining the flux effect and the coating adhesion is improved as the component ratio of NH₄Cl to ZnCl₂ decreases. Zn-Mg-Al alloy-coated steel products treated with the optimized flux composition of NH₄Cl·3ZnCl₂ show superior corrosion resistance compared to Zn-coated steel products, even with a coating weight of 60 %.

• Safety and Health at Work
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• 제14권4호
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• pp.445-450
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• 2023

Background: The impact of COVID-19 infection on workers' work function persists even after the acute phase of the infection. We studied this phenomenon in Japanese workers. Methods: We conducted a one-year prospective cohort study online, starting with a baseline survey in December 2020. We tracked workers without baseline work functioning impairment and incorporated data from 14,421 eligible individuals into the analysis. We estimated the incidence rate ratio for new onset of work functioning impairment due to COVID-19 infection during follow-up, using mixed-effects Poisson regression analysis with robust variance. Results: Participants reporting infection between January and December 2021 showed a significantly higher incidence of new work functioning impairment (adjusted incidence rate ratio: 2.18, 95% confidence interval: 1.75-2.71, p < 0.001). The formality of the recuperation environment correlated with a higher risk of work functioning deterioration in infected individuals (p for trend <0.001). Conclusion: COVID-19-infected workers may continue to experience work difficulties due to persistent, post-acute infection symptoms. Companies and society must urgently provide rehabilitation and social support for people with persistent symptoms, recognizing that COVID-19 is not just a transient acute infection.

• Structural Engineering and Mechanics
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• 제39권6호
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• pp.795-812
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• 2011

Estimation of damage probability of buildings under a future earthquake is an essential issue to ensure the seismic reliability. Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The purpose of this study is to compare the damage probability of R/C buildings with low and high level of strength and ductility through fragility analysis. Two different types of sample buildings have been considered which represent the building types mentioned above. The first one was designed according to TEC-2007 and the latter was designed according to TEC-1975. The pushover curves of sample buildings were obtained via pushover analyses. Using 60 ground motion records, nonlinear time-history analyses of equivalent single degree of freedom systems were performed using bilinear hysteretic model and peak-oriented hysteretic model with stiffness - strength deterioration for each scaled elastic spectral displacement. The damage measure is maximum inter-story drift ratio and each performance level considered in this study has an assumed limit value of damage measure. Discrete damage probabilities were calculated using statistical methods for each considered performance level and elastic spectral displacement. Consequently, continuous fragility curves have been constructed based on the lognormal distribution assumption. Furthermore, the effect of hysteresis model parameters on the damage probability is investigated.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.41-41
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• 2009

We utilized atomic layer deposition (ALD) for the growth of the ZnO channel layers in the oxide thin-film-transistors (TFTs) with a bottom-gate structure using a $SiO_2/p-Si$ substrate. For fundamental study, the effect of the channel thickness and thermal treatment on the TFT performance was investigated. The growth modes for the ALD grown ZnO layer changed from island growth to layer-by-layer growth at thicknesses of > 7.5 nm with highly resistive properties. A channel thickness of 17 nm resulted in the good TFT behavior with an onloff current ratio of > $10^6$ and a field effect mobility of 2.9 without the need for thermal annealing. However, further increases in the channel thickness resulted in a deterioration of the TFT performance or no saturation. The ALD grown ZnO layers showed reduced electrical resistivity and carrier density after thermal treatment in oxygen.

• KIEAE Journal
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• 제15권6호
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• pp.63-68
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• 2015

Purpose: Most if buildings need various repair works for preventing or delaying the deterioration which gives rise to affect the living condition or function after constructed. Therefore, a long-term repair schedule should be planned and a repair cost is required. In this paper, it aimed at providing the statistical forecast model for a repair cost in roof water-proofing work and elevator work using statistical approach with three variables such as number of household, management area and a elapsed year. Data are collected in apartment housings which are located in Seoul area and conducted with interview and questionnaire sheet. Each analyzed work is divided into a partly work and fully work. Results of this study are shown that, first, the regression model takes a multiplying type like a Cobb-Douglas function and is changed into the log-linear type to include the three variable simultaneously. Second, the goodness-of-fit of the repair cost forecasting model has a good statistics in determinant's coefficient and Dubin-Watson value. Third, the management area is stronger factor than other the number of household and an elapsed year in roof water-proofing work and elevator work.

• 한국건축시공학회지
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• 제2권2호
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• pp.121-127
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• 2002

The functions and uses of existing buildings are not properly changing as modern life needs. As a result, the frequent reconstruction(construction after removal) of existing buildings have been done but it became more and more difficult because of strengthening of regulations and systems concerning construction. And also it has several disadvantages like lower plot ratio and site coverage than existed buildings, enormous construction cost, production of waste-construction materials and thoughtless consumption of natural resources, which gives rise to environmental pollution. Therefore renovation is brought to the fore. In Korea, many business buildings were constructed in 1960s-1970s, during the period of high growth. Such buildings needs to be repaired in whole. It is caused by the change of social, economic, and cultural conditions and deterioration of equipments. Therefore renovation meets some necessary conditions; recovery of building functions and extension of building life span. In case study, the present state of renovation in business buildings is 1) Basic safety, for example, fire prevention and crime prevention, is great important. 2) Advanced technology, INS(international news service), IBS(Intelligent Building System), and internationalization, is pursued for adapting to multimedia ages. 3) It tries to promote proficiency, and to save the energy using spatial environment and natural energy(light and sound). Also, improving comfortable level of users and installing equipments for physically handicapped person needs to be considered.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.102-108
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• 2006

On the refutation demanded for a control of various toxic substances. PCBs(poly chlorinated biphenyl) has a fatal poisonous matter in the ecosystem and the environmental pollution as it Is a kind of stable chemical substance. Especially, the gross Product of PCBs is estimated at about one million tonnage all over the world. However it is kept on storing in untreated state, then has a deterioration by the Prolonged storage and a risk of overflowing. Therefore, this research examined the fundamental characteristics of combustion and emission for the target of using the IPA (iso-propyl alcohol) solution as a part of PCBs control. IPA was filled to three kinds of Vessel, i.e. Vessel I, II, and III, and then was investigated as follows combustion shape, flame temperature. mass burning velocity, and PM(Particulate matter). A radial thermometer and a C-A thermocouple measured the flame temperature, and the optical extinction method by using He-Ne laser and the filter weight method used in the PM measurement. As a result, with an increasing of L/S ratio, the flame length become shorter and the burning velocity is more rapid, but the particulate matters is higher. It is supposed that the air flow rate is high on Vessel. and then the combustion is Promoted in the surface area of the upstream zone. The future works plan to investigate the characteristics with an using of the mixing of IPA and PCBs

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.117-122
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• 2001

Recently, epoxy-coated re-bar used to the structure partly and put to practical use step, but not economical and appeared to the defect of deterioration of long term bond strength between concrete. The method for complement the defect of epoxy coated re-bar, study of polymer cement slurry coated re-bar started and basic properties appeared to excellent, but study of bond properties embedded in concrete specimens insufficient until now. This study attempts to examination of using possibility for bond strength of polymer cement slurry coated re-bar between concrete specimens compare to ACI Code and KS Code through pull-out test of 15cm$\times$15cm$\times$15cm specimens with polymer cement slurry coated re-bar as polymer cement ratio 50%, 100%, 150%, coating thickness 250${\mu}{\textrm}{m}$, 440${\mu}{\textrm}{m}$ and curing age. In the results of this study, the bond strength of polymer cement slurry coated re-bar compare to plain re-bar, epoxy coated re-bar decreased St/BA-modified polymer cement slurry coated re-bar, but bond strength of PA-modified polymer cement slurry coated re-bar appeared to excellent results. The bond properties of polymer cement slurry coated re-bar between concrete will be obtain more precise results according to compressive strength change of concrete and re-bar diameter size.

• 콘크리트학회논문집
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• 제11권5호
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• pp.3-10
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• 1999

Earthquake resistant R/C frame structures are generally designed to prevent the columns from plastic hinging. R/C columns under higher axial load or strong earthquake showed a brittle behavior due to the deterioration of strength and stiffness degradation. An experimental study was conducted to examine the behavior and to find the relationship between amounts of lateral reinforcements and compressive strength of ten R/C column specimens subjected to reversed cyclic lateral load and higher axial load. Test results are follows : An increase in the amount of lateral reinforcement results in a significant improvement in both ductility and energy dissipation capacities of columns. R/C columns with sub-tie provide the improved ductility capacity than those with closely spaced lateral reinforcement only. While the load resisting capacity of the high strength R/C columns is higher than the normal strength concrete columns under both an identical ratio of lateral reinforcement, however the ductility capacity of high strength R/C columns is decreased considerably. Therefore, the amounts of lateral reinforcement must be designed carefully to secure the sufficient ductility and economic design of HSC columns under higher axial load.

• 한국전기전자재료학회논문지
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• 제24권7호
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• pp.525-531
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• 2011

In this paper, experimental analyses have been performed to compare the electrical characteristics of n channel LT(low temperature) and HT(high temperature) poly-Si TFTs(polycrystalline silicon thin film transistors) on quartz substrate according to activated step annealing. The size of the particles step annealed at low temperature are bigger than high temperature poly-Si TFTs and measurements show that the electric characteristics those are transconductance, threshold voltage, electric effective mobility, on and off current of step annealed at LT poly-Si TFTs are high more than HT poly-Si TFT's. Especially we can estimated the defect in the activated grade poly crystalline silicon and the grain boundary of LT poly-Si TFT have more high than HT poly-Si TFT's due to high off electric current. Even though the size of particles of step annealed at low temperature, the electrical characteristics of LT poly-Si TFTs were investigated deterioration phenomena that is decrease on/off current ratio depend on high off current due to defects in active silicon layer.