• 대한금속재료학회지
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• 제48권10호
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• pp.893-900
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• 2010

In the present work, the impact loads and their effects on the surface damage under the simultaneous cavitation bubble and solid particle collapses in the sea water have been quantitatively investigated for the austenitic 304 stainless steel by using a vibratory cavitation test device. To do this, angular $SiO_2$ solid particles with an average size of $150{\mu}m$ were dispersed into the test liquid, and the measured impact amplitudes were converted into the impact loads by a steel ball drop test. The maximum impact load was determined to be 28.2 N in the absence of solid particles, but increased to 33.7 N in the presence of solid particles. In addition, the critical impact loads, $L_{crit}$, required to generate pits with sizes greater than $3{\mu}m$ were measured to be 19.6 N and 16.6 N, respectively, for the cavitation bubble collapse and solid particle collapse. As a result of the cavitation erosion test, the incubation time and erosion rate were 1.2 times lower and 1.5 times higher, respectively, by a solid particle collapse compared to those only by the cavitation bubble collapse, indicating a drastic decrease in a resistance to cavitation erosion by the solid particle collapse.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제37권1호
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• pp.21-45
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• 2023

본 연구는 수학교육에서 영향력 있는 논문을 판별하는 기계학습 프로그램 개발 연구이다. 이를 위하여 과학계량학의 관점에서 논문의 영향력을 조명하고, 수학교육 연구 네트워크를 구성하고, 네트워크 중심성 지수인 PageRank로 수학교육 연구의 영향력으로 정의하였다. 영향력 있는 수학교육 연구를 판별하기 위하여 기계학습 모델을 설계하였으며, 이를 이용하여 영향력 있는 논문이 게재된 비율이 높은 학술지를 조사한 결과 Journal for Research in Mathematics Education(25.66%), Educational Studies in Mathematics(22.12%), Zentralblatt für Didaktik der Mathematik(8.46%), Journal of Mathematics Teacher Education(5.8%), Journal of Mathematical Behavior(5.51%) 순으로 나타났다. 수학교육 전문가들이 직접 논문을 읽고 질적으로 평가한 선행연구 결과와 유사한 결과를 기계학습 프로그램으로 도출할 수 있었다. 많은 인원과 시간이 필요했던 수학교육 연구의 영향력 평가를 인공지능을 이용하여 효율적으로 실시할 수 있었다는 점에서 의의가 있다.

• 대기
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• 제24권2호
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• pp.159-171
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• 2014

This study investigated the temporal and spatial characteristics of summertime (June-August) precipitation over Korean peninsula, using Korea Meteorological Administration (KMA)is Automated Synoptic Observing System (ASOS) data for the period of 1973-2010 and Automatic Weather System (AWS) data for the period of 1998-2010.The authors looked through climatological features of the summertime precipitation, then examined the degree of locality of the precipitation, and probable precipitation amount and its return period of 100 years (i.e., an extreme precipitation event). The amount of monthly total precipitation showed increasing trends for all the summer months during the investigated 38-year period. In particular, the increasing trends were more significant for the months of July and August. The increasing trend of July was seen to be more attributable to the increase of precipitation intensity than that of frequency, while the increasing trend of August was seen to be played more importantly by the increase of the precipitation frequency. The e-folding distance, which is calculated using the correlation of the precipitation at the reference station with those at all other stations, revealed that it is August that has the highest locality of hourly precipitation, indicating higher potential of localized heavy rainfall in August compared to other summer months. More localized precipitation was observed over the western parts of the Korean peninsula where terrain is relatively smooth. Using the 38-years long series of maximum daily and hourly precipitation as input for FARD2006 (Frequency Analysis of Rainfall Data Program 2006), it was revealed that precipitation events with either 360 mm $day^{-1}$ or 80 mm $h^{-1}$ can occur with the return period of 100 years over the Korean Peninsula.

• International Journal of Knowledge Content Development & Technology
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• 제6권2호
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• pp.109-147
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• 2016

This study comprehensively analyzed domestic and foreign literature related to the value and impact of libraries on education, social behavior and economic conditions, developed a survey to investigate the librarians' perception of the libraries' value and impact, and accordingly investigated the perception of librarians according to the types of libraries in which they worked, public versus university. The results showed that the impact is greatest on education and literacy with a mean score of 3.98, followed by their social impact with 3.67 and their economic impact with 3.46. When subordinate items were analyzed it was found that the librarians perceived that the role that libraries are playing in the education area is expanding and their impact on reading and literacy is becoming greater and greater. Libraries were viewed as essential elements for education and the education system. When the difference in perception related to the impact of libraries was compared by types of libraries, the librarians in public libraries tended to rate their facilities higher than the librarians working in universities on most of the items.

• 한국자동차공학회논문집
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• 제18권3호
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• pp.69-73
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• 2010

The melt grafting of unsaturated silanes onto polypropylene (PP) in a twin-screw extruder and crosslinking in hot water were studied to enhance impact strength of polypropylene. The influence of grafting formulations on the melt flow rates of grafted PP and the gel percentages of crosslinked PP was investigated. 3-methacryloylpropyltrimethoxysilane (VMMS) unsaturated silane monomer was used. Benzoyl peroxide, (BPO) and Dicumyl peroxide (DCP) were used as an initiator. When benzoyl peroxide (BPO) was used as an initiator, higher gel percentage and impact strength than those of DCP has been observed. The maximum impact strength was obtained with 0.7 phr of BPO and 2phr of VMMS. The value is 8.7 kgf-cm/cm and it is on a parity with the value of with 20 phr of EOR mixed to PP.

• 한국의류산업학회지
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• 제20권4호
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• pp.422-428
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• 2018

In this study, we developed honeycomb pads using foam and polymer gel and verified the impact protection performance of pads for the development of a fall protection pants for elderly women aged 65 and over who have a high risk of fracture due to falls. The results are as follows; In the first experiment, the impact protection performance was evaluated for four honeycomb pad samples (CR foam, EPDM foam, hardness 15 polymer gel, and hardness 30 polymer gel) manufactured to a thickness of 5 mm using a single material. When the force of about 10757N was applied to the specimens, all four pads reduced the impact force to 3100N or less. Polymer gels showed better protection than foam materials. In the second experiment, the thickness of the protective pad was set to 8 mm in order to improve the shock absorbing performance of the protective pad. As a result of evaluating the impact protection performance of the foam single pad and foam gel composite pad, the impact absorbing performance of the foam single pad was better. Finally, four kinds of protection pads were made by assigning the foam single pad and the foam gel composite pad to pants type and underwear type respectively. The pad thickness of the main protection area was set to 8 mm to enhance the protection, and gradually decreased to 5mm and 3mm toward the edge to improve the appearance and fit.

• 아태비즈니스연구
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• 제14권4호
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• pp.217-231
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• 2023

Purpose - The purpose of this study is to determine the impact of workaholism according to personality on the job satisfaction of organizational members. Design/methodology/approach - Workaholism was defined as excessive working and compulsive work, suggesting a negative impact on job satisfaction, while predicting that conscientiousness would alleviate this effect and presented as a hypothesis. The unbalanced panel data constructed based on 19,283 samples of 6,863 people from the Korea Labor Institute's Korea Labor Panel Survey was used. Findings - Both excessive working and compulsive working were found to have a direct negative effect on job satisfaction. Additionally, as a result of verifying the interaction effect of conscientiousness, it was found that the negative impact of excessive work on job satisfaction was moderated and alleviated by conscientiousness. In other words, for employees with high conscientiousness, the negative impact of excessive work on job satisfaction is alleviated and the negative impact of overworking is offset, whereas for employees with low conscientiousness, the negative impact of overworking on job satisfaction is strengthened. Research implications or Originality - This study shows that the impact of workaholism on job satisfaction varies depending on personality. While existing research has treated personality only as a determinant of workaholism, this study contributes to previous research in that it expands the role of personality. In addition, in practical terms, it is suggested that differential treatment based on individual values or personality is necessary.

• 농촌계획
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• 제9권4호
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• pp.9-18
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• 2003

The objectives of the study are to improve techniques for social impact assessment and to suggest their measuring methods to apply in small scale rural development projects. Population, residence, industries, and traffic volumes were selected to measure the social and economic impact assessment of Seongeup agricultural water development project in Jeju Province. Existing data gathering methods were used to estimate the changes of population and traffic volumes. Interview schedule for villagers was applied to estimate the residents' satisfaction to living environments. Interview schedule for experts was applied to estimate agricultural productivity and land price. The results of social and economic impact assessment show that there will be considerable changes in living environments, agricultural productivity, and land price. On the contrary, the project will make little impacts on the changes of population, em-ployment, and traffic volumes.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.49-57
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• 2008

The performance of crash cushion systems is certified through the full scale crash tests by the standard for installation and maintenance guidelines for roadside safety appurtenance. The impact severities of impacting vehicles in collision with crash cushion systems are rated by indices THIV and PHD. Crash test results are considered to study the performance of three crash cushion systems. In case of the frontal impact or the offset frontal impact, the results show that THIV values of three systems are very close to the threshold limit for the occupant protection. Also, the results show that PHD would be improper for the occupant protection performance index. In order to improve the occupant protection performance of crash cushions, ASI needs to be included in the impact severity index.

• International Journal of Aeronautical and Space Sciences
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• 제4권2호
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• pp.26-36
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• 2003

The objective of this study is to enhance neural-network guidance to consider the impact condition. The optimal impact condition in this study is defined as an head-on attack. Missile impact-angle error, which is a measure of the degree to which the missile is not steering for a head-on attack, can also have an influence on the final miss distance. Therefore midcourse guidance is used to navigate the missile, reducing the deviation angle from head on, given some constraints on the missile g performance. A coordinate transformation is introduced to simplify the three-dimensional guidance law and, consequently, to reduce training data. Computer simulation results show that the neural-network guidance law with the coordinate transformation reduces impact-angle errors effectively.