• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.93-100
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• 2014

Steel reinforcement buried in concrete structure in submerged zone does not easily become corroded due to lack of dissolved oxygen. For that reason, accelerated corrosion test in submerged state is performed with an electrochemical method, which is not suitable for actual corrosion mechanism and makes it difficult to find relevance with long-term behavior. In this study, accelerated corrosion test was performed with the temperature and chloride concentration as main variables in order to establish a method for accelerated corrosion test in submerged zone. Corrosion was determined by the result of reinforcement corrosion monitoring based on galvanic potential measurement and half-cell potential method. The accelerated corrosion test result showed that temperature had the most dominant influence. To determine the chloride content, chloride concentration by depth in the test sample was measured. With the same conditions, chloride penetration interpretation was performed by DuCOM, a FEM durability interpretation program. Also, a test was performed to measure dissolved oxygen according to soaking conditions of artificial seawater, which was used for verifying the validity of the accelerated corrosion test result.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.31-37
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• 2017

A synergistic effect was observed in the combination of nitrite and ethanolamines. Ethanolamine is one of the representative organic corrosion inhibitors and can be categorized as adsorption type. However, nitrosamines can form when amines mix with sodium nitrite. Since nitrosamine is a carcinogen, the co-addition of nitrite and ethanolamine will be not practical, and thus, a non-toxic combination of inhibitors shall be needed. In order to maximize the effect of monoethanolamine, we focused on the addition of molybdate. Molybdate has been used to alternate the addition of chromate, but it showed insufficient oxidizing power relative to corrosion inhibitors. This work evaluated the synergistic effect of the co-addition of molybdate and monoethanolamine, and its corrosion mechanism was elucidated. A high concentration of molybdate or monoethanolamine was needed to inhibit the corrosion of ductile cast iron in tap water, but in the case of the co-addition of molybdate and monoethanolamine, a synergistic effect was observed. This synergistic effect could be attributed to the molybdate that partly oxidizes the metallic surface and the monoethanolamine that is simultaneously adsorbed on the graphite surface. This adsorbed layer then acts as the barrier layer that mitigates galvanic corrosion between the graphite and the matrix.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.55.2-55.2
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• 2012

Intensive theoretical and experimental studies have been carried out at Korean Institute of Science and Technology (KIST) on controlling the bio absorbing rate of the Mg alloys with high mechanical strength through tailoring of electrochemical potential. Key technology for retarding the corrosion of the Mg alloys is to equalize the corrosion potentials of the constituent phases in the alloys, which prevented the formation of Galvanic circuit between the constituent phases resulting in remarkable reduction of corrosion rate. By thermodynamic consideration, the possible phases of a given alloy system were identified and their work functions, which are related to their corrosion potentials, were calculated by the first principle calculation. The designed alloys, of which the constituent phases have similar work function, were fabricated by clean melting and extrusion system. The newly developed Mg alloys named as KISTUI-MG showed much lower corrosion rate as well as higher strength than previously developed Mg alloys. Biocompatibility and feasibility of the Mg alloys as orthopedic implant materials were evaluated by in vitro cell viability test, in vitro degradation test of mechanical strength during bio-corrosion, in vivo implantation and continuous observation of the implant during in vivo absorbing procedures. Moreover, the cells attached on the Mg alloys was observed using cryo-FIB (focused ion beam) system without the distortion of cell morphology and its organ through the removal of drying steps essential for the preparation of normal SEM/TEM samples. Our Mg alloys showed excellent biocompatibility satisfying the regulations required for biomedical application without evident hydrogen evolution when it implanted into the muscle, inter spine disk, as well as condyle bone of rat and well contact interface with bone tissue when it was implanted into rat condyle.

• The Journal of Korean Medicine
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• v.26 no.1 s.61
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• pp.123-133
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• 2005

Objective : We investigated the sasang constitutional difference of physiological and psychological response in various thermal environmental conditions. Methods: Among 210 volunteers, 30 healthy subjects were selected through the QSCC II (a questionnaire for constitutional discrimination) and the manual examination of a specialist in sasang constitution. Subjects consisted of 10 each Soyang(少陽), Soeum(少陰), and Taeum(太陽). Experimental environments were set by six different conditions to be $23^{\circ}C,\;50\%\;RH,\;0.lm/s;\;25^{\circ}C,\;25\%\;RH,\;0.lm/s;\;25^{\circ}C,\;50\%\;RH,\;0.lm/s;\;25^{\circ}C,\;50\%\;RH,\;0.4m/s;\;25^{\circ}C,\;75\%\;RH,\;0.1m/s;\;and\;27^{\circ}C,\;50\%\;RH,\;0.1m\s$ (respectively temperature, relative humidity, and wind velocity). Skin temperature, core temperature, heart rate variability (HRV), and galvanic skin response (GSR) were measured for each subject Additionally, subjects were asked about comfort through the questionnaire. Results: From the viewpoint of external temperature sensibility, in all experimental environments, generally the Taeum type feels hotter and the Soeum feels colder than other types. In relative comfort, Soeum types were most sensitive to wind velocity change. From the viewpoint of body temperature, Taeum type was lower and Soyang was higher than other types. The measurements of HRV and GSR showed no difference between the types. Conclusion : The four sasang constitution types showed different responses to various thermal environmental conditions. Accordingly, our research could provide basic data for building the optimal thermal conditions for individuals based on sasang constitution. Consequently, it will help to build a healthy environment for everyday life.

• Journal of the Ergonomics Society of Korea
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• v.25 no.4
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• pp.129-135
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• 2006

he purpose of this study is to measure bio-signal to investigate the driver's physiological response change under real situation using train simulator. The train simulator used in this study is KTX model and according to changes of driving situation, The bio-signal controlled by autonomic nervous system, such as GSR(Galvanic Skin Response), SpO2(Saturation percent O2), HR(Heart Rate), ECG(Electrocardiograph), EEG(Electroencephagram) and movement and response of eye were measured. Statistically significant difference in bio-signal data and eye movement activity pattern were investigated under several different driving speeds using analysis of variance (p<0.05). The GSR and HR value measured in average and mission speed operation is higher than in high-speed operation. β wave of EEG in average speed operation become more activated than in high speed operation. In accordance with a characteristic of rail vehicle, movement and response of eye in high-speed operation requiring relatively simple maneuver become less activated than in either average or mission speed operations. Conclusively, due to more careful driving controls in average and mission speed operation are required than in high-speed operation, level of mental and physical stresses of train driver was increased and observed through changes of bio-signal and eye movement measured in this study.

• Journal of the Korea Computer Graphics Society
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• v.22 no.5
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• pp.37-47
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• 2016

This study evaluate user feedback such as physiological response and facial expression when subjects play a social decision making game with interactive virtual agent partners. In the social decision making game, subjects will invest some of money or credit in one of projects. Their partners (virtual agents) will also invest in one of the projects. They will interact with different kinds of virtual agents which behave reciprocated or unreciprocated behavior while expressing socially affective facial expression. The total money or credit which the subject earns is contingent on partner's choice. From this study, I observed that subject's appraisal of interaction with cooperative/uncooperative (or friendly/unfriendly) virtual agents in an investment game result in increased autonomic and somatic response, and that these responses were observed by physiological signal and facial expression in real time. For assessing user feedback, Photoplethysmography (PPG) sensor, Galvanic skin response (GSR) sensor while capturing front facial image of the subject from web camera were used. After all trials, subjects asked to answer to questions associated with evaluation how much these interaction with virtual agents affect to their appraisals.

• Journal of IKEEE
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• v.21 no.4
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• pp.381-387
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• 2017

Stress at work has become a serious problem affecting many people of different professions, life situations, and age groups. Stress management should start far before the stress start causing illnesses. In this study, studies were conducted to evaluate stress by measuring the Galvanic skin Response(GRS), Electrocardiograph(ECG), and Electroencephalogram(EEG) generated during images and noise stimuli. The GRS amplitude showed that the stress situation was 27.9 % higher than the baseline. And after the stimulus period, the response time of baseline was longer than 71.6 % than the stress situation. The stress response characteristics of the HRV showed that the rate of change in RMSSD was 16.4 %, and the rate of change of the HF Power was 29.7 %. EEG showed that the frequency band was gradually changed to the ${\theta}$ wave band during stress stimulation. We will be able to utilize image stimuli and noise stimuli as an objective indicator of stress and correlation.

• The Journal of Advanced Prosthodontics
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• v.7 no.2
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• pp.129-137
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• 2015

PURPOSE. Squamous cell carcinoma (SCC) of the tongue has a relatively high incidence of all oral cancers. Some studies have reported a relationship between intraoral dental prosthesis and SCC of the tongue; however, this relationship remains controversial. The purpose of this study was to investigate the relationship between SCC of the tongue and the positional aspects of dental prosthesis using a retrospective analysis. MATERIALS AND METHODS. A total of 439 patients with SCC of the tongue were diagnosed and treated in the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. Patients were treated over a 12.5-year period ranging from January 1, 2001 to June 30, 2013. Statistical analysis was performed to examine potential differences between the groups. RESULTS. The number of patients with a crown and/or a bridge (134, 63.5%) was significantly different than the number of patients without a prosthesis (77, 36.5%). Even after accounting for different types of prostheses such as crowns, bridges, and dentures, no significant differences were observed between the position of the prosthesis and the location of the SCC of the tongue, with significance defined as a P-value less than .05 by the Pearson-Chi square test. CONCLUSION. Patients with crowns and/or bridges exhibited more frequent SCC of the tongue compared with patients without these prosthesis. These data support the hypothesis that mechanical trauma and galvanic phenomena play a role in the etiology of SCC of the tongue.

• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.221-224
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• 2008

This paper describes the equivalent dipole modeling method utilizing a singular value decomposition technique from analysis data by the FNREMUS Detailled Modeller software based on BEM which can predict the underwater electric field signal due to a galvanic corrosion phenomenon on a naval vessel. The proposed dipole modeling method was successfully verified in good agreement with predicted BEM data at 30 m depths through the comparison of average differences. The proposed dipole modelling method can be effectively used in the prediction and analysis of static electric field signature distributions generated from a naval vessel at any different depths.

• Journal of Korea Ship Safrty Technology Authority
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• s.22
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• pp.34-53
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• 2007

In the case of hull material. large sized merchant ships are made of steel, on the other hand FRP or wood are used for small sized fishing boats. At present in Korea approximately 88,500 fishing boats are in operation of which 70% are made of FRP In the meantime, stainless steel is frequently used as shaft materials of the small-size FRP fishing boat. Namely, the kinds of shaft materials are STS 304(18Cr-8Ni), STS 316(18Cr-12Ni-2.5Mo steel) and STS 630(17Cr-Ni-Nb steel)etc. Among these things, STS 304 which is the cheapest and having ordinary corrosion resistance is most widely used as 2nd class shaft material. But, using STS 304 for shaft system material of the small-size FRP fishing boat on seawater environments entails a severe corrosion which causes shaft system troubles. Particularly, the corrosions tend to be concentrated of the stern and bow side, propeller shaft surface of inside of stern tube and the boat having no stern cooling pipe line system. As a solution for those problems, research on the ways to mitigate corrosion on the part of 2nd class stainless steel shaft have been undertaken. In the result, not only clarification for the reason of corrosion of the part of stainless steel shaft used mainly for the small-size FRP fishing boat was done, but also most optimal corrosion protection system was developed by experimenting shaft's protection simulation based of the electrochemical cathodic protection principle. In addition, verification through the field test on the optimal cathodic corrosion protection method by means of aluminum sacrificial anode was carried out. In this study, effective and economical shaft's protection system is suggested to the small-size FRP fishing boat operator by substantiating the results obtained from the research on the optimal cathodic protection.