• 한국주조공학회지
• /
• 제17권3호
• /
• pp.276-285
• /
• 1997

The effect of wheel surface condition on solidification behavior of Al-Cu ribbon was investigated in order to establish extreme levels of heat extraction. The condition of wheel surface was changed either by heating the wheel surface up to $200^{\circ}C$ or by coating boron nitride(BN) onto the the rim of a wheel. Heating the wheel surface up to $200^{\circ}C$ improved the wetting behavior between the molten metal and the rotating wheel, leading to an increase in the ratio of columnar structure to the entire thickness of Al-4.3wt%Cu and Al-33.2wt%Cu ribbons. For Al-4.3wt%Cu ribbon, assuming one grain as a single heterogeneous nucleation event at the contact point, the nucleation density with the wheel surface heated to $200^{\circ}C$, was $4{\times}10^6/mm^2$, and in the cases of BN coating with thin and thick layers, $10^5/mm^2$ and $5{\times}10^4/mm^2$, respectively. The largest cooling capacity of the wheel corresponded to the heated wheel surface, and as the thickness of BN coating layer increased, the cooling capacity of the wheel gradually decreased.

• 한국항공우주학회지
• /
• 제32권5호
• /
• pp.84-90
• /
• 2004

양성자 가속기를 이용한 지상 실험에 기초하여 인공위성에서 사용할 마이크로프로세서의 SEE 발생률을 예측하였다. 우주 공간의 하전 입자 분포를 AP8, JPL91 그리고 CREME 모델을 사용하여 추정하고, 양성자 가속기를 통한 실험에서 얻어진 단면적 곡선들을 SEE 발생률 예측에 사용하였다. 약 685 km의 저궤도에 대해 고 경사각과 저 경사각이 고려되었다. 계산 결과는 후보 소자에 대한 SEE 발생률이 저 경사각에서는 수용할만한 것이었지만 고 경사각의 경우에는 최악의 조건에서 문제될 수 있음을 보여준다.

• Nuclear Engineering and Technology
• /
• 제53권3호
• /
• pp.967-973
• /
• 2021

In 2011, an earthquake and subsequent tsunami hit the Fukushima Daiichi Nuclear Power Plant, causing simultaneous accidents in several reactors. This accident shows us that if there are several reactors on site, the seismic risk to multiple units is important to consider, in addition to that to single units in isolation. When a seismic event occurs, a seismic-failure correlation exists between the nuclear power plant's structures, systems, and components (SSCs) due to their seismic-response and seismic-capacity correlations. Therefore, it is necessary to evaluate the multi-unit seismic risk by considering the SSCs' seismic-failure-correlation effect. In this study, a methodology is proposed to obtain the seismic-response-correlation coefficient between SSCs to calculate the risk to multi-unit facilities. This coefficient is calculated from a probabilistic multi-unit seismic-response analysis. The seismic-response and seismic-failure-correlation coefficients of the emergency diesel generators installed within the units are successfully derived via the proposed method. In addition, the distribution of the seismic-response-correlation coefficient was observed as a function of the distance between SSCs of various dynamic characteristics. It is demonstrated that the proposed methodology can reasonably derive the seismic-response-correlation coefficient between SSCs, which is the input data for multi-unit seismic probabilistic safety assessment.

• 전기전자학회논문지
• /
• 제25권2호
• /
• pp.330-336
• /
• 2021

하드웨어 이중화 구성 수를 줄이는 대표적인 방법은 마이크로컨트롤러로 고장을 검출, 식별 및 수용을 위한 해석적 기법으로 구현하는 것이다. 본 논문에서는 해석적 기법 중 하나인 고장 검출 필터를 항공기 터보팬 엔진 시스템에 적용하였다. 고장 검출 필터는 특수한 형태의 관측기로써 특정한 고장 발생시 잔차가 출력 공간에서 일정한 방향을 유지함으로써 고장의 위치 판별이 가능한 장점이 있다. 이에 본 논문에서는 터보팬 엔진 내 공기 터빈 시스템의 단일 입출력 동적 시스템 모델링, 고장 검출 필터 설계 및 이를 적용한 모의실험 결과를 나타내었다. 모의실험 결과를 통해 고장 검출 필터가 갖는 방향성에 대한 민감성 효과로 고장 검출이 유효하게 적용될 수 있음을 보였다.

• 초등상담연구
• /
• 제6권1호
• /
• pp.193-215
• /
• 2007

The purpose of this study was to identify the effect of the Peer Relationship Program on the school adjustment of Ha-nul with the school maladjustment by peer problems. To achieve this purpose, single subject pretest-pottiest design was implemented for Ha-nul with school maladjustment in the third grade of the elementary school. As for the testing period of this study, this program was carried out one time a week for 10 weeks from Sept 11, 2006 to Oct 13, 2006. Each test lasted for $40{\sim}60$ minutes. To find out changes in the school adjustment of the subject child, the progress in change before and after tests was comparatively analyzed through a Likert-type three-step evaluation scale and presented as tables and graphs regarding the target behavior table. And the school adjustability was calculated in terms of percentage and presented as tables and bar graphs through a Likert-type four-step evaluation scale. Change in the subject Ha-nul's behavior, which was shown in test scenes, was observed and recorded and then Qualitatively analyzed. The following conclusions were drawn from the results of this study: First, the Peer relationship improvement program was effective in the positive influence to the relationship between a teacher in charge and Ha-nul with the school maladjustment This program made a confidence and increased the ability to express one's own ideas and feelings to others. Second, the Peer relationship improvement program was effective in the positive influence to the relationship between schoolfellows and Ha-nul with the school maladjustment This program provided the opportunities to get along with peers naturally and the abilities of a mutual understanding. Third, the Peer relationship improvement program was effective in the partially positive influence to Ha-nul with the school maladjustment. Fourth, the Peer relationship improvement program was effective in the positive influence to follow the school rules by experiencing a role, concession and fairness through the various activities. Fifth, the Peer relationship improvement program was effective in the positive influence to take part in the school event with a self-confidence and cooperation with peers through the various activities.

• 한국잠사곤충학회지
• /
• 제5권
• /
• pp.1-5
• /
• 1965

추잠기의 적엽이 익춘의 불발아와 접목의 활착에 미치는 영향을 조사하여 다음과 같은 결과를 얻었다. (1) 추잠기의 적엽은 익춘의 불발아비율을 증대시키는 원인이 되며 특히 전적엽을 하면 적엽을 하지 않은 것에 비하여 불발아비율이 46%나 증대한다. 그리고 동일한 기조에서 일부분의 엽을 여러가지 방법로 적채하였을 경우에 있어서도 적엽을 한 부분의 불발아율이 적을 하지 않은 부분의 그것 보다 크다. (2) 추잠기의 적엽은 익춘에 그 동아를 일아근접하였을 때에 있어서 그 활착비율을 크게 저하하며 동일지조에 있어서 여러가지 방법으로 적엽을 하였을 경우에 있어서도 적엽을 한부분의 동아의 활착이 적엽을 하지 않은 부분의 보다 항상 좋지 않다. (3) 추잠기에 적엽을 하면 익춘잠기의 수량을 7∼20％ 저하시키며 특히 기조의 하반부적엽(20%)과 전적엽구(12％)가 그 정도가 심하다.

• 천문학회지
• /
• 제29권2호
• /
• pp.119-136
• /
• 1996

To examine the effect of neighboring galaxies on the gravitational lensing statistics, we performed numerical simulations of lensing by many galaxies. The models consist of a galaxy in the rich cluster like Coma, or a galaxy surrounded by field galaxies in $\Omega_0 = 1$ universe with $\Omega_{gal} = 0.1,\;\Omega_{gal} = 0.3\;or\;\Omega_{gal}=1.0\;,\;where\;\Omega_{gal}$ is the total mass in galaxies. Field galaxies either have the same mass or follow Schechter luminosity function and luminosity-velocity relation. Each lensing galaxy is assumed to be singular isothermal sphere (SIS) with finite cutoff radius. In most simulations, the lensing is mainly due to the single galaxy. But in $\Omega_{gal} = 3$ universe, one out of five simulations have 'collective lensing' event in which more than two galaxies collectively produce multiple images. These cases cannot be incorporated into the simple 'standard' lensing statistics calculations. In cases where 'collective lensing' does not occur, distribution of image separation changes from delta function to bimodal distribution due to shear induced by the surrounding galaxies. The amount of spread in the distribution is from a few $\%\;up\;to\;50\%$ of the mean image separation in case when the galaxy is in the Coma-like cluster or when the galaxy is in the field with $\Omega_{gal} = 0.1\;or\;\Omega_{gal}=0.3.$ The mean of the image separation changes less than $5\%$ compared with a single lens case. Cross section for multiple image lensing turns out to be relatively insensitive to the presence of the neighboring galaxies, changing less than $5\%$ for Coma-like cluster and $\Omega_{gal}=0.1,\;0.3$ universe cases. So we conclude that Coma-like cluster or field galaxies whose total mass density $\Omega_{gal}<0.3$ do not significantly affect the probability of multiple image lensing if we exclude the 'collective lensing' cases. However, the distribution of the image separations can be significantly affected especially if the 'collective lensing' cases are included. Therefore, the effects of surrounding galaxies may not be negligible when statistics of lensing is used to deduce the cosmological informations.

• 천문학회보
• /
• 제37권2호
• /
• pp.108.2-108.2
• /
• 2012

Recent results from microlensing surveys show that a free-floating planet or a wide-separation planet is more numerous than a main-sequence star in the Galaxy. Moreover, the detection efficiency of the planets will be improved in next-generation experiments with a high survey monitoring frequency. However, microlensing events produced by both planets appear similar light curves with a short duration timescale, thus it is difficult to distinguish them. In this paper, we investigated the detectable separation range of a wide-separation planet as the planet bound to its host star. We construct the fractional deviation maps using the magnifications of the planetary lensing and the single-lensing by planet itself for various parameters such as a mass ratio, separation, and source radius. As a result, we found that the pattern of the fractional deviation is related to the ratio of source radius to caustic size, and the ratio satisfying the detection criterion (i.e., ${\geq}5%$ in the fractional deviation) varies with a separation. Hence, we derived a fitting formula as the function of a mass ratio and a source radius to reflect the variation in the calculations of the detectable separation range of a wide-separation planet as the planet bound to its host star. In addition, we estimated the condition that a wide-separation planet can be detected as a single-lensing event under the finite source effect. We found that such a case is possible provided that the source radius is smaller than ~2.5 times of Einstein ring radius of a planet, regardless of a separation or a mass ratio.

• 한국산학기술학회논문지
• /
• 제14권7호
• /
• pp.3358-3367
• /
• 2013

본 연구는 충청북도 소재 일개 대학교 간호학과에 재학 중인 2학년 학생 88명(실험군: 47명, 대조군: 41명)을 대상으로 노인환자 유사체험의 효과를 검정하기 위해 수행되었으며 결과변수로는 노인 및 노인환자에 대한 태도와 공감 정도가 측정되었다. 연구 결과 노인환자 유사체험은 간호대학생의 노인 및 노인환자에 대한 태도에는 유의한 효과를 미치지 못하였으나 공감 수준을 향상시키는데 효과가 있는 것으로 나타났다. 또한 대상자들은 노인환자 유사체험에 대한 제한점으로 1회성의 단편적 경험, 노화에 대한 불안감 야기, 체험복장의 현실감 부족, 체험 과정 중의 사고 위험성 등을 제시하였고 이러한 제한점이 유사체험의 긍정적 효과를 약화시킬 수 있는 것으로 제기되었다. 따라서 이러한 제한점들을 고려하여 중재 프로그램을 개선하여 제공한다면 중재가 간호 대학생들의 노인환자에 대한 긍정적 태도와 공감적 이해증진으로 이어지는데 크게 기여할 것으로 판단되었다.

• 대한한의학회지
• /
• 제37권2호
• /
• pp.53-61
• /
• 2016

Objectives: Considering high prevalence of myopia in Asian countries, social cost paid for myopia may gradually increase in Korea. However, studies for developing myopia treatment are deficient. The study was to evaluate whether the periocular acupressure with a medical massager is effective for suppressing myopia progression. Methods: This study was an investigator-sponsored, prospective, open-labeled, and superiority pre and post single-armed study. 14 myopia children aged 7-12 years wore a medical massager for 15 minutes to stimulate periocular acupoints. For 24 weeks, the participants used the device twice a day. Based on prior studies, the refraction change of naturally proceeded myopia was set as -0.38 D. The axial length change of naturally proceeded myopia was set as 0.228 mm. To assess the safety, we performed vital sign check, physical examination, visual acuity test, slit lamp examination, IOP measurement, and fundus examination. Results: The refraction and axial length of the participants increased. For 24 weeks, the change in refraction was -0.38 D at the right eye and -0.40 D at the left. The change in axial length was 0.21 mm at the right and 0.22 mm at the left. In the safety assessment, any adverse event did not occur. Conclusions: There was no significant difference between the control group and the intervention group. The effect of growth may have more contributed to our result than that of acupressure. Based on our result, a full-scale study will not be conducted.