• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.133-137
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• 2001

In this research, we synthesized various photo-crosslinkable polyimide based polymers. The control of pretilt angles for a nematic liquid crystal (NLC) using the photodimerization method on the photopolymers was studied. A good thermal stability of the photopolymers was measured by thermogravimetric analysis (TGA) measurement until 450C. High pretilt angles of the NLC were otained by polarized UV exposure on the photopolymers containing biphenyl (BP), decyl (de), and cholesteryl (chal) groups, respectively. However, low pretilt angles of the NLC were measured by polarized UV exposure on the photopolymers containing fluorine and chalcone groups. The high NLC pretilt angles generated are attributable to the biphenyl and alkyl moieties, and the photodimerized chalocone group of the photopolymers. Additionally, good voltage-transmittance and response time characteristics were observed by UV exposure on the photopolymers.

• Korean Journal of Child Studies
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• v.25 no.2
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• pp.93-108
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• 2004

This study investigated personality and environmental variables influencing peer bullying by sex and by differences between bullies, victims, bully-victims, and normal children. Findings were that the proportion of the total sample involved in peer bullying was 47.88%. Of the bullying children, 38.15% were bully-victims, followed by victims and bullies. The bullying of both boys and girls was influenced by exposure to violence, delinquent friends, and peer support. Bullies had higher levels of aggression and exposure to violence than normal children and higher levels of peer support than victims. Victims had higher levels of delinquent friends and exposure to violence than normal children. Bully-victims showed higher levels of aggression, immaturity, delinquent friends, exposure to violence and lower levels of peer support than normal children.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.333-336
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• 2006

In general, polymer materials undergo degradation when exposed to ultraviolet radiation, which can cause dissociation of chemical bonds. FRP composites which are used in strengthening existing structure are usually adhered on the concrete surface, its mechanical properties as well as appearance such as color, surface conditions are affected by sunlight and expecially ultraviolet light. In this study, variations of tensile strength after exposure for certain period of time through accelerated exposure by Xe arc methods specified in KS F 2274 are measured in order to examine strength degradation characteristics of FRP composite. As a result of ultraviolet light test for FRP composite after accelerated exposure for 0, 500, 1000, 1500 hour, discoloration of FRP composite occurs according to the passage of time. But, few strength degradations of FRP composite are observed due to exposure of ultraviolet ray with an small variation of tensile strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.249-254
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• 1998

Recently, high quality architectural concrete, i.e., appearance of natural stone and a marbling effect, is needed, to achieve high quality glassy reflective surface for outer wall of the building. In this study to achieve above characteristics of the "glossing exposure concrete" we developed a form practice and the best mix proportion and derived the optimistic removal time of form to bring out the durable glassy reflective surface and durable concrete. Hereby with the "glossing exposure concrete" obtained we applicate for first time, to Electronics and Telecommunications Research Institute situated on Taedok Science Town and it will be the beginning of the construction of "glossing exposure concrete" in this country.oncrete" in this country.ntry.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.129-133
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• 1998

This paper deals with a characteristic of output for high frequency resonant inverter type x-ray generator in short exposure time. In the same tube-voltage, the waveform is stable in long exposure time (200msec) but more decreasing exposure time (50msec), the waveform is distorted. The ripple factor of tube-voltage waveform distorted more and more increase tube-voltage and in this case output is also unstable. High-frequency resonant inverter type X-ray generator using PSU source which introduced in resent is stable tube-voltage waveform and low ripple factor.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2652-2660
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• 2021

The gamma-ray exposure doses in decontamination operation after a nuclear accident were evaluated with a consideration of various geometrical conditions and specific gamma-ray energies. The calculation domain is organized with three residence types and each form is divided into two kinds of geometrical arrangements. The position-wise air KERMA values were calculated with an assumption of evenly distributed gamma-ray source based on Monte Carlo radiation transport analysis using the MCNP code. The radioactivity is initially set to be unity to be multiplied by the deposition value measured in the actual accident condition. The workforce data set depending on the target object was determined by modifying the Fukushima report. The external exposure doses for decontamination workers were derived from the calculated KERMA values and the workforce analysis. These results can be used to efficiently determine the workforce required by the characteristics of the area and the structure to be decontaminated within the dose limits.

• The Research Journal of the Costume Culture
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• v.18 no.2
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• pp.229-244
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• 2010

This study aims to discuss the type and characteristics of primitivism in the modern fashion of the $21^{st}$ century and, as a research method, the concept of primitivism as well as the transition of the patterns of primitivism expressed in modern art have been considered and reviewed through a variety of references. In particular, an empirical analysis of the works that have been created from 2000 to 2009 has been performed using domestic and overseas fashion and collection magazines. The characteristics of primitivism in modern fashion possess the following types of expression: First, Sensuality can be cited as one of the characteristics, either by using direct or indirect exposure of the human body, a silhouette which fits tightly to the body, or creating the effect of sensual beauty using animal fur or bird feathers. Second, Incantation: Masks symbolizing primitive incantation are used to cover the human face or primitive incantation is incorporated as a theme of hair accessories or fashion trinkets, etc. In addition, such decorations as tattoos and the body colorations of ancient tribes are reproduced in modern fashion by means of body painting, printing or other accessories, emphasizing the image of occult primitiveness. Third, Naturalness can be cited as one of the characteristics. Naturalness is emphasized in modern fashion not through artificial decorations and processing, but rather through different patterns of exposure by which natural purity can be felt or through the use of non-artificial materials which recalls primitive civilization. Forth, Playfulness is expressed in the form of graffiti or abstract letters and paintings, and the character of the play is often expressed by the use of grotesque images based on various distortions and exaggerations of the human body, the utilization of symbols of primitive incantation and body and/or facial painting. Fifth, Lastly 'folkishness is emphasized. Folk-like objects, facial decorations, exposure of the body and intense color contrasts typically represent the folkish characteristics.

• Journal of Environmental Health Sciences
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• v.48 no.6
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• pp.324-330
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• 2022

Background: Lung injuries due to exposure to humidifier disinfectants (HDs) were reported in 2011 in South Korea. As a result of the government's epidemiological investigation and toxicity test study, it was found that HDs caused health damage such as lung disease. Objectives: The purpose of this study was to classify HD exposure ratings and analyze the affecting factors that could identify the relationship with lung disease. Methods: Exposure assessment for HDs was conducted using a questionnaire during face-to-face interviews with the applicants. Ratings of high exposure (Class 1) and low exposure (Class 2) were cross-tabulated with clinical ratings (acceptable and unacceptable). Logistic regression analysis was carried out by setting the clinical rating of lung disease as a dependent variable and the socio-demographic and exposure characteristics obtained through the questionnaire as independent variables. Results: The concentration in air of polyhexamethylene guanidine (PHMG) was 71.96±107.47 ㎍/m³, and the exposure concentration was 15.21±23.28 ㎍/m³ . The exposure rating was overestimated with 97.1% of affected subjects having high exposure using margin of exposure (MOE), but only 9.9% matching the clinical class. In the overestimated group, it could be explained by the fact that the exposure time was long and the subjects had already recovered from damage symptoms. As a result of logistic regression analysis, ten variables were found to be significant influencing factors. Conclusions: A new exposure rating could be calculated based on the MOE, and factors affecting lung disease could be estimated through comparative evaluation with the clinical rating.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.773-784
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• 2008

Even if the exploitation of copper slag produced during the smelting process of copper as aggregate for construction purpose has been permitted since 2004 in Korea, the lack of sufficient data enabling to evaluate its long-term stability that is its durability has to date impeded its application. This study intends to investigate experimentally the durability characteristics of 18 and 27 MPa-class commercial concretes in which natural sand (fine aggregates) has been partially replaced by copper slag through accelerated and exposure tests so as to provide bases promoting the application of copper slag concrete. The experimental results revealed insignificant difference of the durability characteristics in most of the mix proportions in which 30% of natural sand was replaced by copper slag. In the case where crushed sand was adopted, tests verified similar characteristics for replacement ratio of 50%. Particularly, the results of the exposure test conducted during 8 years demonstrated that equivalent level of durability was secured compared to the case using natural sand. In the case of 18MPa-class lower grade concrete, exposure test verified also that the physical lifetime similar to 50 years could be secured until carbonation reaches cover depth of 20 mm.

• Korean Journal of Occupational Health Nursing
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• v.23 no.4
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• pp.277-286
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• 2014

Purpose: In this study, I am going to figure out Korean workers' actual exposure to risk factors and percentage of the workers who complain of health problems by performing a comparative analysis of the characteristics of the workers and working conditions in Korea and EU. Methods: The data used in this study includes the $1^{st}$ working conditions survey conducted in 2006 in Korea, the $2^{nd}$ working conditions survey in 2010, the $4^{th}$ EU working conditions survey, and the $5^{th}$ EU working conditions survey. I have compared the changes to Korean working conditions and those to EU working conditions in the categories of demographic characteristics, quality of labor, exposure to risk factors, and health problems included in the data. Results: The analysis of the characteristics of the demographic characters of Korean workers shows that aged and female workers register increased labor force participation. The analysis of labor quality shows that Korea has a long working time but with a lower work intensity compared to the countries included in EU working conditions survey. As for risk factors, Korea registers a low level of exposure as compared to countries included in EU working conditions survey and characteristically shows a decreasing exposure to tobacco smoke. The survey shows sharply increasing complaints of muscle pain in the upper and lower limbs. Conclusion: In this study, I have identified vulnerable social groups by using quantified values in a comparison of the working conditions of Korea and those of EU.