• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.227-235
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• 2007

The railway catenary is softer in the middle of a span than at the end. This stiffness variation induce the vertical motion of a moving pantograph, which results in the large variation of contact forces. To reduce the vertical motion of a pantograph, we can introduce a pre-sag of the contact wire. The pre-sag changes merely equilibrium position of the contact wire. Because the pantograph must follow the sag added to the motion of the contact wire, the sag gives downward forces to the pantograph. If the pre-sag is proper, the variation of the vertical motion of the pantograph is reduced. However, excessive sag worses the current collection performance because the pantograph receives too large downward forces by the contact wire. The objective of the paper is to establish the theoretical basis to understand how the pre-sag affect the contact force variation and to propose the proper sag for the railway catenary for the train speed up to 200 km/h.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
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• pp.25-29
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• 2003

Pre-treatment of Bi-2223/Ag tapes has been investigated to improve the superconducting property and grain alignment. However, rolling deformability of Bi-2223/Ag wires was degraded by the breakage of Ag alloy sheath after pre-treatment. Various pre-treatment conditions were tried to prevent the problem of sliver sheath and improve the superconducting property of Bi-2223/Ag tapes. Filament precursor of Bi-2223/Ag tapes was modified to be textured easily during main sintering by the optimum pre-treatment with low oxygen pressure and up to $800^{\circ}C$. Critical current was also increased up to 20% than that of no pre-treated tape.

• 한국건설관리학회논문집
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• 제13권2호
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• pp.80-90
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• 2012

2011년을 기준으로 국내 건설시장은 민간 부문과 공공부문의 발주 감소로 전반적인 건설 경기 침체가 되고 있는 실정이며 해외 건설의 경우는 플랜트에 편중된 시장 점유로 인해 전체 건설업에 대해서는 중국 및 인도 등에 경쟁력을 잃어가고 있다. 또한 선진국에 비해 고부가가치 기술경쟁력이 열위에 있는 상황에서 국내 건설사들의 경쟁력 강화에 대한 연구들이 이루어지고 있는데, 최근 국내 외에서 Pre-construction Service(이하 Pre-con Service)의 중요성이 부각되어 대형 건축 및 플랜트 프로젝트 발주 시 이를 통한 발주가 늘어나는 추세이다. 그러나 국내 건설사들의 Pre-con 업무에 대한 일반적인 이해부족과 업무 체계 정립이 미흡하여 Pre-con Service에 대한 대응 전략은 부족한 상황이다. 이에 본 연구에서는 국내 건설사의 해외 건설 시장 진출을 위한 Pre-con Service의 핵심 업무를 규명하고 그 중요도와 현 역량 수준을 비교 분석하여 이에 따른 역량 향상의 방향을 제시하고자 한다.

• 한국생활과학회지
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• 제16권2호
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• pp.315-331
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• 2007

The purpose of this study is to examine current situations about and factors related to expenditures of private education among pre-school children and to provide policy implications useful for future pre-school children education. The subjects of the study were parents of pre-school children under seven years of age, who lived in Seoul and Incheon area. The survey was conducted using parent questionnaire. The major findings of the study are: First, 86.8% of parents of pre-school children use private education and the average expenditure on it was 154, 446 won. Second, major factors determining their private education expenditure are educational level of parents, parents' job characteristics, household income, and region. Third, the most important reason for using private education among parents is to improve and excel in academic performance of their children. Forth, the higher the parents' expected returns from private education are, the higher the expenditure level of private education is. Fitth, the results of the logistic regressions showed that parents' attitudes toward private education was the most important factor in determining household economic burden associated with private education. The odds were 5 times greater for the parent group with strong desire for private education than for the parent group without it and 1.2 times greater for the parent group with high-expected returns from private education than the parent group without it. In conclusion, systematic, universal educational policies need to be developed to provide and support all the parents with pre-school children, given that their current economic burden is substantial. By providing such support, we can help parents focus on public education. This study examining current situations about and determining factors related to private education expenditures among pre-school children collected data limiting only Seoul and Inchoen area, therefore, future studies need to include data collected nationwide for generalizability of the findings. As well, development of more elaborated survey instruments and analytical methods would advance our understanding in the field.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.65-67
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• 2003

The critical current of Bi-2223/Ag HTS wire could be improved by the second phase modification pre-treatment (SPMT). On the other hand, the pre-treatment conditions are possible to affect to the degradation of silver alloy sheath, such as brittleness. Chlorine was detected at the outer sheath of wire by Auger observation, we also have tried to search new pre-treatment conditions that do not affect the degradation of silver sheath but, improve the critical current of the wire.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.89-95
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• 2014

This study presented the benefit of the pre-ventilation using solar sunroof with integrated photovoltaic. Recent year, auto-makers make an effort to enhance the fuel efficiency and moreover to clean the cabin passenger's health. Solar energy, one of the alternative energies, adapted in automotive air handling system, in order to pre-ventilation when vehicle parked under the sun in summer. The power generated by a prototype solar sunroof has been used to run blower in a air handing system. And the solar sunroof was installed in a vehicle, and evaluated to find out benefit of the pre-ventilation. The effect of reducing the cabin temperature about $3^{\circ}C{\sim}10^{\circ}C$ with 20 ~ 40W power generator from solar sunroof were obtained in the pre-ventilation test. This reduced thermal load can lead to the reduction of air-conditioning operation time than that of current car. Moreover, fuel economy may increase as a results of the short use of the air-conditioning time. Additionally, Total Volatile Organic Compounds in the cabin is reduced maximum 80% than that of the current vehicle.

• Corrosion Science and Technology
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• 제22권4호
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• pp.297-303
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• 2023

This study aimed to evaluate hydrogen permeation behaviors of pre-strained twinning-induced plasticity steel with or without Zn coating using electrochemical permeation technique. In contrast to un-strained and 30% strained samples, permeation current density was measured in the 60% strained sample. Tensile pre-straining at 60% involved microstructural modifications, including a high level of dislocation density and stacking fault with a semi-coherent twin boundary, which might provide a high diffusion path for hydrogen atoms. However, reproducibility of measurements of hydrogen permeation current was low due to non-uniform deformation and localized stress concentration. On the other hand, the permeation current was not measured in pre-strained TWIP steel with Zn coating. Instead, numerous blisters with some cracks were observed on the surface of the coating layer. In locally damaged Zn coating under tensile straining, hydrogen atoms could relatively easily permeate through the coating layer. However, they were trapped at the interface between the coating layer and the substrate, which might delay hydrogen penetration into the steel substrate.

• Journal of Genetic Medicine
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• 제14권2호
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• pp.49-55
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• 2017

Pre-eclampsia is known to cause considerable maternal morbidity and mortality. Thus, many studies have examined the etiopathogenesis of pre-eclampsia. While many pathophysiological factors related to pre-eclampsia have been identified, the precise etiopathogenesis of pre-eclampsia remains unclear. Numerous studies have identified factors for the early prediction for pre-eclampsia to lead to preparation and closer observation on pre-eclampsia when it occurs. This article reviews on current studies of biomarkers and genetic factors related to pre-eclampsia, which may be important for developing strategies for early prediction of pre-eclampsia.

• 한국초등과학교육학회지:초등과학교육
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• 제30권4호
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• pp.524-534
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• 2011

This study is to ascertain pre-service teachers' conceptions for the causes of season change, to verify their conceptional mistakes, and to analyze how their conceptions are changed while presenting Disproof-Experiment Model where they cannot explain it with their current conceptions. 32 junior students of Education universities, pre-service elementary teachers, located at the middle of Korea participated in this research including two interviews and one experiment activity. As a result of analyzing of the data, the pre-service teachers held diverse conceptions for the causes of season change such as to mistake the phenomena, the distance between the earth and the sun, the tilting of the rotation axis and the revolving around the sun while changing the tilting direction of the rotation axis as the cause. After applying Disproof-Experiment Model designed by the researchers in order to change the current conception above, the conception changes of the pre-service teachers were investigated. Diverse Disproof-Experiment Models were used differently depending on the pre-service teachers' conceptions. As a result of the application of Disproof-Experiment Model, 26 out of 28 pre-service teachers were changed to scientific conceptions. It was determined that in order to modify pre-service teachers' conceptions, designing and presenting the Disproof-Experiment Model appropriate to their conceptions are effective after analyzing their conceptions. In case of conceptions that pre-service teachers feel difficult, it was established that unraveling experiment models prescribed after investigating the preconceptions and identifying the misconceptions are important.

• Asian Pacific Journal of Cancer Prevention
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• 제14권2호
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• pp.805-810
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• 2013

Increasing the rate of smoking cessation will reduce the burden of diseases related to smoking, including cancer. Understanding the process of smoking cessation is a pre-requisite to planning and developing effective programs to enhance the rate of smoking cessation.The aims of the study were to determine the demographic distribution of smokers across the initial stages of smoking cessation (the pre-contemplation and contemplation stages) and to identify the predictors of smoking cessation among Malaysian adult smokers. Data were extracted from a population-based, cross-sectional survey carried out from April 2006 to July 2006. The distribution of 2,716,743 current smokers across the pre-contemplation stage (no intention to quit smoking in the next six months) or contemplation stage (intended to quit smoking in the next six months) was described. Multivariable logistic regression analysis was used to examine the relationship between socio-demographic variables and the stages of smoking cessation. Of the 2,716,743 current smokers, approximately 30% and 70% were in the pre-contemplative and contemplative stages of smoking cessation respectively. Multivariable analysis showed that male gender, low education level, older age group, married and those from higher income group and number of cigarettes smoked were associated with higher likelihood of pre-contemplation to cease smoking in the next six months. The majority of current smokers in Malaysia were in the contemplative stage of smoking cessation. Specific interventions should be implemented to ensure the pre-contemplative smokers proceed to the contemplative stage and eventually to the preparation stage.