• Journal of the Korea Convergence Society
• /
• v.9 no.11
• /
• pp.145-152
• /
• 2018

The purpose of this study was to reveal association between health behavior practice and jab characteristics on periodontal disease of employees. The analysis was conducted on 1,737 of above the age of nineteen in employees by using raw data from the 2015 National Health and Nutrition Survey. The data were analyzed using SPSS for windows version 24.0. Smoking, BMI and aerobic exercise in health behavior practice had statistically significant difference. Occupation, work status and regular work in jab characteristics had statistically significant difference. In conclusion, business owners need active management to health behavior practice their employees and the government needs to resolve the polarization of medical services through the development of oral health care policies for low-income people.

• Journal of Korean society of Dental Hygiene
• /
• v.19 no.4
• /
• pp.565-575
• /
• 2019

Objectives: In this study, both subjective and objective levels of oral health were used to identify the relationship between oral health inequalities. Methods: Korean National Health and Nutritional Examination Survey data from 2013 to 2015 were combined to create an analysis plan. Oral health questions categorized as subjective oral health conditions and oral health-related diseases used dental tissue disease status as data measured by the Community Periodical Index(CPI) and decayed, missing, filled teeth(DMFT) experience. Other data on oral health behaviors such as toothache experience, the frequency of toothbrush use, chewing problems, oral examination status, and unmet dental care needs were classified and analyzed according to the socioeconomic level. Data were analyzed using frequency and cross analyses, and the statistical significance level was set at 0.05. Results: It was found that higher the economic and educational level, better was the subjective oral health, lower the CPI, lower the experience of toothache, higher the frequency of toothbrush use, lower the number of people having chewing problems, and higher the frequency of oral checkups. Conclusions: Oral health inequality exists among social classes. It is suggested that continuous research and efforts be carried out to promote oral health while considering socioeconomic and educational levels. Further, active government efforts will be needed to address polarization by social class.

• Corrosion Science and Technology
• /
• v.20 no.6
• /
• pp.373-383
• /
• 2021

The effect of Cr addition to high Mn steel on flow-accelerated corrosion (FAC) behavior in a neutral aqueous environment was evaluated. For comparison, two types of conventional ferritic steels (API X70 steel and 9% Ni steel) were used. A range of experiments (electrochemical polarization and impedance tests, weight loss measurement, and metallographic observation of corrosion scale) were conducted. This study showed that high Mn steel with 3% Cr exhibited the highest resistance to FAC presumably due to the formation of a bi-layer scale structure composed of an inner Cr enriched Fe oxide and an outer Mn substituted partially with Fe oxide on the surface. Although the high Mn steels had the lowest corrosion resistance at the initial corrosion stage due to rapid dissolution kinetics of Mn elements on their surface, the kinetics of inner scale (i.e. Cr enriched Fe oxide) formation on Cr-bearing high Mn steel was faster in dynamic flowing condition compared to stagnant condition. On the other hand, the corrosion scales formed on API X70 and 9% Ni steels did not provide sufficient anti-corrosion function during the prolonged exposure to dynamic flowing conditions.

• Journal of the Korean institute of surface engineering
• /
• v.41 no.5
• /
• pp.181-188
• /
• 2008

A.C. impedance properties of HA/Ti compound layer coated Ti-30Ta-($3{\sim}15$)Nb alloys have been studied by electrochemical method. Ti-30Ta binary alloys contained 3, 7, 10 and 15 wt% Nb were manufactured by the vacuum furnace system. And then specimen was homogenized at $1000^{\circ}C$ for 24 hrs. The sample was cut and polished for corrosion test and coating. It was coated with HA/Ti compound layer by magnetron sputter. The non-coated and coated morphology of Ti alloy were analyzed by X-ray diffractometer (XRD), energy X-ray dispersive spectroscopy (EDX) and filed emission scanning electron microscope (FE-SEM). The corrosion behaviors were investigated using A.C. impedance test (PARSTAT 2273, USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. Ti-30Ta-($3{\sim}15\;wt%$)Nb alloys showed the ${\alpha}+{\beta}$ phase, and $\beta$ phase peak was predominantly appeared in the case of increasingly Nb contents. The microstructures of Ti alloy were transformed from needle-like structure to equiaxed structure as Nb content increased. From the analysis of coating surface, HA/Ti composite surface uniformed coating layer with 750 nm thickness. The growth directions of film were (211), (112), (300) and (202) for HA/Ti composite coating on the surface after heat treatment at $550^{\circ}C$, whereas, the growth direction of film was (110) for Ti coating. The polarization resistance ($R_p$) of HA/Ti composite coated Ti-alloys were higher than those of the Ti and HA coated samples in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. Especially, corrosion resistance of Ti-Ta-Nb system increased as Nb content increased.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.8
• /
• pp.877-885
• /
• 2013

A seawater pipe of the engine room in the ships is being surrounded with severely corrosive environments caused by fast flowing of the seawater, containing aggressive chloride ion and high conductivity etc.. Therefore, the leakage of the seawater from its pipe have been often occurred due to its local corrosion by aggressive chloride ions. Subsequently, its leakage area is usually welded by AC shielded metal arc welding with various electrodes. In this study, when the sea water pipe is welded with several types of electrodes such as E4301, E4311, E4313 and E4316, a difference of the corrosion resistance on the welding metal zones was investigated using an electrochemical method, observing microstructure, measuring polarization behaviors and hardness. The weld metal zone welded with E4313 electrode exhibited the lowest value of hardness compared to other weld metal zones. In addition, its zone indicated also the best corrosion resistance than those of other weld metal zones. Furthermore, all of the weld metal zones revealed a relatively better corrosion resistance than those of the base metal zones. and also showed higher hardness than the base metal zones.

• Journal of the Korean Electrochemical Society
• /
• v.7 no.1
• /
• pp.21-25
• /
• 2004

The electrochemical behaviors of dissolved hydrogen and hydrogen peroxide at a platinum disk electrode were investigated in boric acid solution by potentiostatic polarization method at the temperature of 25 and $200^{\circ}C$. The oxidation of dissolved hydrogen at $25^{\circ}C$ was kinetically controlled reaction, the rate of which depends upon the electron transfer on the electrode surface. As temperature was raised, however, the electrochemical characteristics of dissolved hydrogen were changed from a kinetically controlled reaction to a diffusion controlled one. One notable feature, with dissolved hydrogen at high temperature, is that an abnormal potential range was observed, where the oxidation rate of dissolved hydrogen rapidly decreased just before starting potential of water oxidation. We think it is caused by the deactivation of the electrode that results from the adsorption of hydroxyl ion on the surface of the platinum disk. On the contrary, a definite change with temperature was not identified in the case of the hydrogen peroxide except for the increase in current density that was due to the increasing diffusion coefcient with an increase of temperature.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.11
• /
• pp.47-54
• /
• 2006

Shear wave velocity of uncemented soil can be expressed as the function of effective stresses when capillary phenomena are negligible. However, the terms of effective stresses are divided into the direction of wave propagation and polarization because stress states are generally anisotropy. The shear wave velocities are affected by ${\alpha}$ parameters and ${\beta}$ exponents that are experimentally determined. The ${\beta}$ exponents are controlled by contact effects of particulate materials (sizes, shapes, and structures of particles) and the ${\alpha}$ parameters are changed by contact behaviors among particles, material properties of particles, and type of packing (i.e., void ratio and coordination number). In this study, consolidation tests are performed by using clay, mica and sand specimens. Shear wave velocities are measured during consolidation tests to investigate the stress-induced and inherent anisotropies by using bender elements. Results show the shear wave velocity depends on the stress-induced anisotropy for round particles. Furthermore, the shear wave velocity is dependent on particle alignment under the constant evvective stress. This study suggests that the shear wave velocity and the shear modulus should be carefully estimated and used for the design and construction of geotechnical structures.