• Journal of Korean Society for Atmospheric Environment
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• v.22 no.4
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• pp.487-498
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• 2006

Total 438 precipitation samples were collected in Jeju City between 1997 and 2005, and their major ionic components were analyzed. The comparison tests using ion balance, electric conductivity and acid fraction were performed. It was found their correlation coefficients were in the range of 0.977$\sim$0.994, indicating the good quality of collected dam. The volume-weighted mean pH and electric conductivity were 4.8 and 23.0 $\mu$S/cm, respectively. with the ionic strength of 0.23$\pm$0.20 mM. The marine ($Na^+$, $Mg^{2+}$, and $CI^-$), anthropogenic (nss$SO_4{2-}$, $NO_3^-$, and $NH_4^+$) and soil (nss-$Ca^{2+}$) species have contributed to the ionic components of precipitation samples with 43$\sim$74%, 16$\sim$37% and $\sim$5%, respectively. The seasonal variations of $NO_3^-$ and nss-$SO_4^{2-}$ showed a distinct seasonality with higher concentrations in winter than summer, indicating an increase of fossil fuel consumption and a possibility of long-range transport of those pollutants from continental area along the dominant winter westerly. The levels of nss-$Ca^{2+}$ also were appeared the highest in winter and increased comparatively in spring season. possibly due to the soil influences including the Asian Dust. The acidification contribution of nss-$SO_4^{2-}$ and $NO_3^-$ showed 88$\sim$96%, and the free acidity was in the range of 6.0$\sim$40.1%. Interestingly, the backward trajectories for the case of upper 10% nss-$SO_4^{2-}$ and $NO_3^-$ levels have passed through the China continent before their arrival to Jeju. The precipitation of pH below 4.5 has been occurred frequently when the trajectory's path lied over the China continents. On the other hand, the air masses from the North Pacific area were characterized by lower 10% of nss-$SO_4^{2-}$- and $NO_3^-$ concentration, which demonstrated that air mass from the North Pacific was the cleanest among air masses moved to Jeju.

• Korean Journal of Biological Psychiatry
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• v.8 no.2
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• pp.258-265
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• 2001

Objectives : Chronic alcohol consumption has been known to result in various neurocognitive deficits. Many neuropsychological studies revealed that the major disturbances occurred in the executive function, learning and short-term memory, visuospatial performance function, perceptuo-motor skills, and abstraction and problem solving abilities. This study was done to identify which cognitive areas might be mainly affected. Methods : The cognitive disturbance was evaluated using the Korean Version of the Mini Mental State Examination(MMSEK) and the 7 Minute Screen(7MS) in male inpatients with alcohol dependence(N=3 : as well as in age and education level matched healthy male controls(N=30). Four individual tests of the 7MS were consisted of the Benton Temporal Orientation Test, the Enhanced Cued Recall, the Clock Drawing and the Category Fluency. Results : 1) The average scores of four individual test of the 7MS for the alcoholics were $2.77{\pm}4.38$ for the Benton Temporal Orientation Test, $13.90{\pm}2.02$ for the Memory Test(the Cued Recall $6.77{\pm}1.94$, the Uncued Recall $7.10{\pm}2.45$), $5.84{\pm}1.86$ for the Clock Drawing, and $12.58{\pm}3.29$ for the Category Fluency. Except the Benton Temporal Orientation Test, there were statistically significant differences between test scores of alcoholics and those of controls(p<0.01). 2) The alcoholics who had MMSE-K score <24 were 9.68%. The average(${\pm}S.D.$) score of the MMSE-K for the patient group($27.23{\pm}2.62$) was significantly(p<0.001) lower than that of the healthy controls($29.20{\pm}1.24$). There were no statistically significant differences between four individual test scores of the 7MS of alcoholics with the MMSE-K score <24(N=3) and those of alcoholics with the MMSE-K score ${\geq}24$(N=28). 3) Four individual test scores of the 7MS seemed to have statistically significant association with such variables as MMSE-K, duration of alcohol drinking, blood magnesium concentration, liver function and thyroid function. Conclusion : Mild deficits of cognitive areas such as orientation, memory, visuospatial abilities and verbal fluency could be found in alcohol dependence.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.845-854
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• 2008

The old bridge of Woljeong-gyo, which has the fluvial history and culture, represents the ancient construction and civil engineering techniques. It is the oldest stone bridge in Korea and currently restored with its vicinities. In this study, the experimental model was used to analyze the hydraulic characteristics, the local pier-scour depth without scour protection, and the stability of riprap protection using the old grid type panels and stones for Woljeong-gyo of the study area. The water levels were increased around 30cm due to the restored bridge piers and foundations and the effects went up to 200m upstream. The maximum scour depth of 5.4m was measured and the scour protection tests were performed with the riprap size calculated using empirical equations and the existing scour protection range. The riprap of the existing scour protection in the upstream side was broken away, while the riprap of extended scour protection was very stable for the design flood condition of Woljeong-gyo area.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.153-162
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• 2009

The main compositions of "Seokganju", a Korean traditional red mineral pigment, are iron oxides. To investigate its mineralogical and functional properties, we had got its ore from Juto cave in Ulreoung island, which was a famous field of it in Korean documents. The ore occurs as a paleosol between the olivine basalt and amphibole trachyte in discontinuously. It is reddish brown and yellowish brown and consists mainly of clay minerals with minor debris. Its reddish and yellowish brown color are due to the hematite and ferrihydrate, respectively. These iron oxides are precipitated as ferrihydrate from the ferrous water in the paleosol and partly changed to hematite. The color reproduced in timber by using seokganju pigment with traditional tools and methods is similar to that in heritage building. The moistureproofing and fire resistance of Ulreungdo seokganju is far better than that of artificial seokganju. Moreover, the combustion tests show that the artificial seokganju promote the ignition and combustion of the timber. Ulreungdo seokganju is regarded as a pigment with fungicidal efficacy because growth of two wood decay fungi (cov. and typ.) are inhibited in solid medium with it.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.200-207
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• 2016

The automotive seat is an important component that moves in sync with the driver and is actively being developed with various new functions. The aim of this work is to develop a lightweight seat cushion extension module using a lightweight material. To this end, a structural strength analysis, vertical strength test, and durability test were conducted. In the structural analysis, the maximum value of deformation under vertical load was 4.98 mm at the front of the upper panel. The maximum stress was approximately 105 MPa, which occurred at the point of contact between the upper and lower panels of the module. The vertical strength test showed a maximum vertical deformation of 5.31 mm under a vertical load, which differed from the analysis results by approximately 6.45%. The structural safety of the product was verified by the fact that it showed no harmful deformation or damage during operation after the vertical strength test and a durability test for 20,000 cycles. Furthermore, the use of engineering plastics made it possible to reduce the weight by approximately 30% compared to existing products. The lack of damage after tests verified the passenger safety, strength, and rigidity of the product. The results are expected to be applied for improving environmental and fuel efficiency regulations and preventing accidents due to driver fatigue. The applications of this module could be expanded various types of vehicles, as well as other industries in which eco-friendly and lightweight materials are used.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.535-545
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• 2019

The PBA of ship weapon system should be installed and operated under harsh environmental conditions and so it should be highly reliable to endure the mission profiles during its entire lifetime. In the case of PBA failure during operation, rapid maintenance is highly likely to be difficult due to problems such as supply of parts, which can have a devastating effect on the mission. In order to validate the reliability of PBA, a series of tests are performed with PBA samples, but they require time, testing facilities, samples, expenses and failure analysis if failed. The reliability of PBA is predicted on the basis of specifications such as MIL-HDBK-217F, but this specification does not take into account failure mechanisms for specific design details, environment and usage, interconnects and its characteristics that drive many failures of PBA in the field. Therefore, this study predicts the reliability of PBA using an RPA tool and proposes the RPA methodology as a validation process at the design stage. With RPA, it is now possible to achieve design validation including inherent failure mechanism, identification of weakest link, alternative design options, and test plan development.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.447-452
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• 2020

The purpose of this research was to confirm that prefrontal neurofeedback training has an impact on adolescents. The objective of this study was to prove its scientific effect through experimentation. The effect of the training was measured by the difference in neuro?frequencies before and after the training. For this research, an experimental group and a control group, each with 22 students in J High School located in the city of S participated in this study. From May to July 2019, the training was conducted three times a week and for 30 minutes per session. The neuro?frequency data collected were analyzed through the methods of F.F.T. The resulting changes from the neurofeedback training for each group were analyzed by T-Tests. The result of the study is as follows; Neurofeedback training has had a positive effect on adolescent attention and sleep. In conclusion, the environmental and educational factors also play an important role. As the interaction of the latter two factors yield an individual's unique brain structure and functionality, the impact of the neurofeedback training is important on adolescents. The derivation of the above results by utilizing scientific and objective methods reemphasizes the importance of this study.

• Environmental and Resource Economics Review
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• v.13 no.3
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• pp.499-518
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• 2004

This study tests four hypotheses on management performance of environment-friendly firms. The hypotheses are that i) environment-friendly firms are lower management performance than general firms, ii) high cost environment-friendly firms are lower management performance than lower cost ones, small and medium environment-friendly firms lower management performance than large ones, and long-term environment-friendly firms higher management performance than short-term ones. The major findings are that the first hypothesis is not supported at the 5% significance level and the second one is also not supported at the 10% significance level. The third one is supported in terms of stability since large firms are more stable small and medium ones at the 5% significance level. The last one is not supported since short-term environment-friendly firms are more stable than long-term ones in the 10% significance level.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.1
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• pp.65-72
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• 1983

Dry sand specimens for both normally consolidated and overconsolidated triaxial compression tests were prestressed on the path with five different coefficients of earth pressure 1.0, 3/4, 0.55, $K_0$ and 1/3. Deformation resistance of normally consolidated sand increased with increasing the initial stress for all coefficients of earth pressure during consolidation, and the deformation modulus at a certain initial stress showed a tendency to increase with increasing the coefficient of earth pressure. And deformation moduli($E_i$, $E_{50}$), were found to be proportional to the $n_{th}$ power of initial stresses[${\sigma}_{m0}{^{\prime}}$, ${\sigma}_{10}{^{\prime}}$, ${\sigma}_{30}{^{\prime}}$, $({\sigma}_1-{\sigma}_3)_0$] for both isotropically and anisotropically normally consolidated samples, where n varied from 0.37 to 0.92. Overconsolidated sand with the higher overconsolidation ratio showed the higher deformation modulus. It is concluded that the $K_0$-anisotropically consolidated triaxial compression test is necessary to obtain the more accurate value of in-situ deformation modulus.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.3
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• pp.127-136
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• 1985

A simplified single degree of freedom analog with mass-spring-dashpot is proposed in this study. The simplified analog can describe the dynamic behavior of a rigid circular footings whose contact pressures are parabolic. The analog proposed in this study shows remarkable agreement when compared with the elastic half-space theory the analog is also compared with vertical vibration test results of model concrete footings. For the vibration experiments, 11 circular footings with different mass ratio are constructed. The elastic half-space is represented by compacted sand layer. A constant force excitation vibrator is used for the dynamic loading. The frequency range for vibration tests is 30 to 100 Hz. From the dynamic experiments, it is found that the measured resonant frequencies agree very well with the analog results, however, the ratio of theoretical and measured resonant amplitudes vary between 0.5 and 1.7. It is also found that, when the dynamic force is increased, the resonant frequency is decreased slightly and the resonant amplitude is increased slightly.