• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.45-53
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• 2009

More than 40% of railway bridges on the conventional lines in Korea consist of track-on-steel plate girder (TOSPG) bridges. This type of bridge is typically designed without considering seismic loadings, as most of them were built before 1970. The seismic performance of this particular type of bridge could be upgraded through various seismic retrofit schemes, and seismic risk assessment could play a key role in decision-making on the level of the seismic retrofit. This study performed a seismic risk assessment of TOSPG bridges in Korea. The seismic damage of several crucial components of TOSPG bridges--fixed bearings, free bearings, and piers--were probabilistically estimated, and their seismic fragility curves were developed. The probability that the components would exceed their predefined limit states was also calculated by combining the fragility curves and the seismic hazard function. The analysis showed that the piers of TOSPG bridges, which are made of plain concrete without rebars, have relatively low risk against seismic loadings in Korea. This is because the mass of the superstructures of TOSPG bridges is relatively small, and hence, the seismic loading being transferred to the piers is minimal. The line-type bearings typically used for TOSPG bridges, however, are exposed to a degree of seismic risk. Among the bearings, the probability of the free-end bearings and the fixed-end bearings exceeding the slight damage state in 50 years was found to be 12.78% and 4.23%, respectively. The gap between these probability values lessened towards more serious damage states. This study could effectively provide an engineering background for decision-making activities on the seismic retrofit of railway bridges.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.317-322
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• 2010

In this study, poly(methyl methacrylate) (PMMA) was treated with changing mixing ratios of $F_2$ and $O_2$ using oxyfluorination method for hydrophilic modification of PMMA film. For the characterizations of oxyfluorinated PMMA surface, contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS) and optical transmittance (UV-vis) were carried out. After the oxyfluorination, PMMA surface became more hydrophilic showing the decrease of water contact angle from $69^{\circ}$ to $44^{\circ}$. So, surface free energy of oxyfluorinated PMMA film was increased from 46 to $58\;mN\;m^{-1}$. These results are attributed to hydrophilic functional groups such as hydroxyl group formed oxyfluorination method on the PMMA surface. From XPS results, it was confirmed that O/C concentration ratio on the surface of PMMA was increased, the amount of C-OH bonding which shows hydrophilicity was also largely increased from 6.7 to 24.8% with increasing fluorine partial-pressure via the oxyfluorination, The oxyfluorination conditions, room temperature, 1 bar with one mixture ratio of $F_2$ to $O_2$ had little influence on optical transmittance properties of PMMA film but enhanced its surface hydrophilicity. This result suggests that oxyfluorination method could be useful to change hydrophobic PMMA surface to hydrophilic.

• Sijohaknonchong
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• v.30
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• pp.9-20
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• 2009

The purpose of this study is to consider factors such as one's sight of viewing afar, expressional principles, and basic aesthetic category, which are treated importantly by the poets of the Joseon Dynasty era in appreciating nature. 'Afar' of the viewing afar is actual distance and aesthetic distance at the same time. Viewing afar is to find geographical features, depth, and details of a mountain, seeing the whole nature at a high place. Also, it can make possible escape from the external limitation of nature and get mental superiority and enhancement. Ultimately, viewing afar is to find out everlasting change of the nature and reason of natural creation. One's sight in viewing afar makes an appreciator's mind empty and calm, and it makes chance to harmonize human with nature. Viewing afar is to unite human nature to naturality beyond realistic value, idea, and artificiality. The mind from viewing afar has peacefulness and it is a state of serenity without any secular atmosphere. Viewing afar is an eye for beauty to leap toward an endless free state from narrow sight about objects. It rejects modification and technics in achieving an world of harmony. It means that objects should not be restrained by human's recognition. There are three expressions, which are high, horizontal, and transcendental viewing afar. The aesthetic category and beauty of peaceful mental state are realized by the expressions. The peaceful mental state makes peaceful mind from realistic conflicts and makes us experience a profound reason of nature.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.196-202
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• 2000

Top synthetic spin valves with structure Ta/NiFe/CoFe/Cu/CoFe(P1)/Ru/CoFe(P2)/FeMn/Ta on Si(100) substrate with natural oxide were prepared by dc magnetron sputtering system, and investigated on the magnetoresistance properties and effective exchange bias field. As the thickness of FeMn increased above 150 $\AA$, MR ratio was decreased due to the current shunting effect. As the thickness of free layer decreased below 40$\AA$, MR ratio was reduced rapidly. In case of 40 $\AA$ thick of free layer, spin valve film with a structure Si(100)/Ta(50 $\AA$)/NiFe(27 $\AA$)/CoFe(13 $\AA$)/Cu(26 $\AA$)/CoFe(30 $\AA$)/Ru(7 $\AA$)/CoFe(15 $\AA$)/FeMn(100 $\AA$)/Ta(50 $\AA$) exhibited maximum MR ratio of 7.5 % and an effective exchange bias field of 600 Oe, respectively. Thickness difference dependence in this synthetic spin valve structure on effective exchange field was investigated and interpreted by the analytical method. It should be noted that thickness increase of CoFe(P 1) and decrease of CoFe(P2) in synthetic antiferromagnet leaded to the decrease in effective exchange bias field by experimentally and analytically.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.210-219
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• 2000

The magnetoresistance characteristics of FeN/Co/Cu/Co and FeN/Co/Cu/Co/Cu/Co/FeN multilayers using ferromagnetic iron-nitrides (FeN) has been studied. The microstructure of FeN film is the mixed ${\alpha}$-Fe and $\varepsilon$-Fe$_3$N phase on the condition that the flow rate of N$_2$ gas is over 0.4 sccm. The magnetoresistance effect is observed because of shape magnetic anisotropy induced by needle-shaped $\varepsilon$-Fe$_3$N phase. This magnetoresistance effect changes, because the degree that the shape magnetic anisotropy adheres to the adjacent Co pinned layer is varied according to the flow rate of N$_2$ gas and the thickness of FeN film. The best magnetoresistance effect is obtained on the condition that the thickness of Co free layer is 70 ${\AA}$ and the maximum MR ratio(%) value of 3.2% shows in the FeN(250 ${\AA}$)/Co(70 ${\AA}$)/Cu(25 ${\AA}$)/Co(70 ${\AA}$)/Cu(25 ${\AA}$)/Co(70 ${\AA}$)/FeN(250 ${\AA}$) mutilayer film which is fabricated at the N, gas flow rate of 0.5 sccm and the FeN film thickness of 250 ${\AA}$. Four steps are observed in the magnetoresistance curve owing to this difference of coercive force, because respective magnetic layers in the multilayer possess different coercive forces. These effects observed in these mutilayer films can be expected to application to the memory device the same MRAM as can carry out simultaneously four signals.

• Sijohaknonchong
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• v.23
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• pp.33-48
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• 2005

In my paper, the discussion focuses on the fact that sijo is distinguished from free verse as a separate Identity in that it has its own formal beauty, and the works that deviate from this poetic rule are guarded against. In the past ancient sijo, in terms of both music and literature, was a major genre in harmony with chang(songs) ; and in modern times, sijo been created irrelevantly with chug. But my point is that it will not futile if sijo is accompanied with chang, and, therefore, the latter should be adjusted to a modern taste and go together with the former ; and that, to attain this goal, Korean musicans should cooperate with sijo writers. With English-version sijo works, there are some that are put in accordance with the formality of Engish poetry. This paper indicates that, in this case, foreign readers can't feel the nuances the source text of sijo works could produce, so it is not proper to translate sijo works in accordance with the formality of English poetry. But there are other translations where the 3-jang(statements)-6-gu(phrases) form of the original sijo text is reproduced within the limits of English expressions, with each of the two gu(phrases) in a ing(statement) having an almost equal number of syllables, so that each phrase could be recited within the same length of time. The conclusion is that the Korean-English translations of sijo works should begin with the reproduction of its original formal beauty; but, to do this, sijo writers should create works in accordance with it original formality first. Therefore for good translations of sijo works there should be a mutual efforts between sijo scholars and English poetry scholars.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.251-258
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• 2018

In construction site, conventional methods such as jackhammer or explosive methods(dynamite) have been often used for the demolition of structures. Use of those methods are more carefully treated in environmentally and historically sensitive area. For those reasons, use of Soundless Chemical Demolition Agent(SCDA) is getting the spotlight. The SCDA is a powder which has expansive strength when it is mixed with water. In these Characteristics, SCDA can destroy the concrete or rock as it is poured into boreholes of the concrete or rock structures. However, there is no industrial standard for the use of SCDA effectively yet. In this study, experimental study to measure the expansive pressure was conducted depending on various boundary conditions such as waterproof, length of the steel pipe, submerged of steel pipe. Furthermore, computational analysis using damage plasticity model to predict the minimum required pressure of the SCDA for the concrete demolition depending on spacing between holes(k-factor) and compressive strength of the concrete was conducted. Obtained results indicates that water heat dissipation with submerged steel pipe shows the stable pressure for measuring the SCDA and hole distance(k-factor) is the most important factor for crack initiation of concrete.

• Korean Journal of Comparative Education
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• v.24 no.3
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• pp.199-226
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• 2014

The aim of this study was to determine key experiences of homestay guardians of unaccompanied minor Korean adolescents studying abroad in the United States through qualitative research method of grounded theory methodology. This study identified guardianship experiences and the process of adjustment to life with homestay students through in-depth interviews with 12 subjects who are Korean guardians in the United States. The results of this study classified "started with concern" as a category that leads guardians to start providing homestay accommodation, and "other's recommendation," "need for financial support," and "unexpectedly" as subcategories. This study identified "act as a mediator to resolve differences" as a key experience of guardians, and classified subcategories are "parental role" and "calculation of gains and losses" on a personal level; and "feel sorry for own children," "limited leeway of the family," and "formation of relationship between own children and homestay students" on a family level. Developed subcategories are "thirsty for attention," "vulnerability," "task on freedom and control," and "regrettable feeling in the absence of communication" with respect to relationship with students; "grade expectations," "one-way communication," "trapped between parents' and students' demands" in regard to relationship with parents; and "advice from school" in the aspect of school. "Cultural difference," "preparedness of students and parents," "age differences between guardian's children and students," "family support," "similar personalities," "guardian's motivation," and "parent's attitude" are subcategories that affect central phenomenon of guardians.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.124-127
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• 2007

Magnetic tunnel junctions (MTJs), which consisted of amorphous CoFeSiB layers, were investigated. The CoFeSiB layers were used to substitute for the traditionally used CoFe and/or NiFe layers with an emphasis given on understanding the effect of the amorphous free layer on the switching characteristics of the MTJs. CoFeSiB has a lower saturation magnetization ($M_s\;:\;560\;emu/cm^3$) and a higher anisotropy constant ($K_u\;:\;2800\;erg/cm^3$) than CoFe and NiFe, respectively. An exchange coupling energy ($J_{ex}$) of $-0.003\;erg/cm^2$ was observed by inserting a 1.0 nm Ru layer in between CoFeSiB layers. In the Si/$SiO_2$/Ta 45/Ru 9.5/IrMn 10/CoFe 7/$AlO_x$/CoFeSiB 7 or CoFeSiB (t)/Ru 1.0/CoFeSiB (7-t)/Ru 60 (in nm) MTJs structure, it was found that the size dependence of the switching field originated in the lower $J_{ex}$ using the experimental and simulation results. The CoFeSiB synthetic antiferromagnet structures were proved to be beneficial for the switching characteristics such as reducing the coercivity ($H_c$) and increasing the sensitivity in micrometer size, even in submicrometer sized elements.

• Korean journal of applied entomology
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• v.60 no.4
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• pp.493-502
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• 2021

We examined American consumers' perceptions and attitudes toward edible insect-based pet food. In this study, 16 Americans in Korea who owned dogs were categorized into two groups, and focus-group discussions were conducted under three conditions. First, we observed the free association perception of edible insect-based pet food, and attitudes were analyzed after providing a newspaper article related to it. Finally, consumer attitude was examined in the context of purchasing. The study found that the participants had high awareness of the eco-friendliness of edible insects and showed a positive attitude toward news articles related to it. However, when it came to purchasing, they considered nutritional and health functional values compared to environmental values. Meanwhile, the rejection of insects was nevertheless the most important negative factor in pet food, as in general food. The results are significant in confirming the possibility of using insect-based pet food by examining the perceptions and attitudes toward the environmental, nutritional, and health functional values of edible insects under three conditions for American consumers.