• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.32-40
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• 2018

In order to avoid excessive vibration, it is required to carry out a vibration analysis of heat-exchanger/nuclear-reactor at the design stage. Information of eigen-frequency in the vibration problem is required to evaluate safety of heat-exchange/nuclear reactor. This paper describes a numerical method, Galerkin's method, to solve the eigenvalue problem occurred in a cantilever beam. The beam is restrained with added mass and spring at the free end or a node point of a mode shape. The numerical results of eigen-frequency were compared with simple analytical and experimental results given by simple approach and simple test, respectively. It is found that Galerkin's method is applicable to estimate the eigen-frequency of the cantilever beam. The frequencies become lower with increasing the added mass and the frequencies increase with the spring force. It is shown the heavy added mass has a role of support on the flexible tube. The eigen-frequency of the first mode, for the system with the added mass mounted at the free end, can be calculated by the approximate analytical method existing with more or less accuracy.

• The Journal of the Korea Contents Association
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• v.17 no.2
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• pp.687-695
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• 2017

This study tried to confirm the effective intervention to reduce drinking frequency and problem behaviors among the three interventions; school based, feedback, and behavior change. Meta-analysis was conducted targeting at 16 studies of randomized controlled trial in which alcohol intervention has been applied to adolescent. The drinking frequency and problem behaviors were analyzed by follow up period. There was a significant difference in the feedback intervention to reduce the frequency of drinking under 3 months of follow up period. Also, there was a significant difference in the feedback intervention to reduce the problematic behaviors of drinking between 4 and 12 months of follow up period(p<.05). The study confirmed that feedback intervention is effective in reducing the frequency of drinking during the follow up period under 3 months, and it is effective in reducing the problem behaviors of drinking during the 4~12 months of follow up period. Also, the study confirmed that school-based intervention and feedback intervention were useful in reducing and preventing harmful effects of drinking by adolescents.

• Journal of Families and Better Life
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• v.10 no.1 s.19
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• pp.115-130
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• 1992

The purpose of this study is ; 1) to identify the overall levels of family problem and stress perceived by urban homemakers, 2) to investigate the relations between them. For the purpose of this study, the samples were chosen among 369 homemakers living in Seoul. These data were analyzed by Frequency, mean, t-test, F-test, Duncan's Multiple Rang test and pearson's correlation. The significant results are as follows : 1) urban homemakers perceive 'economic problem' as the highest level, 'children problem' as the second one and 'health problem' as the lowest one in family life problem. There is significant difference in family problem perception according to education level, husband's job, children's numbers, and living level. 2) There is not sigificant difference in stress level according to independence variables. 3) There are positive correlations between the family problem perception and stress level of urban homemakers. In conclusion, we come to know every field of family life effects homemakers as stressors. According, it is necessary for us to understand and prevent family life problem in order to release stress perceived by homemakers.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.215-218
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• 2004

The pseudolites are ground-based transmitters that can be configured to emit GPS-like signals with the purpose of enhancing the GPS by providing increased accuracy, integrity, and availability. Although the use of the pseudolites offers many potentially significant benefits, a number of technical issues must also be addressed. One is the pseudolite signal power level which is related with near-far problem, and other issues include deployment requirements, signal data rate, signal integrity monitoring, and user antenna location and sensitivity. In order to solve the near-far problem, the frequency offset or the pulsing schemes is implemented in most the pseudolites. However, in the case of the previous pulsing scheme with the fixed code pattern, the near-far problem still remains. This paper aims to design a sequential pulsing scheme to avoid the near-far problem. A pulse mode pseudolite has less interference than the continuous mode.

• Korean Journal of Child Studies
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• v.26 no.2
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• pp.193-207
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• 2005

The present research studied children's coping strategies by age, sex, and frequency of victimization and examined the relationship of coping strategies to loneliness in peer victimization. Participants were 434 children from the 3rd to 6th grades of an urban elementary school. Self-report data indicated seven types of coping strategies : cognitive distancing, adult support seeking, peer support seeking, negative problem solving, positive problem solving, internalizing, and externalizing. With increasing age, children used less adult support seeking and more positive problem solving. While girls used more adult and peer support seeking, boys employed more externalizing and negative problem solving. Children with higher victimization frequencies were more likely to use negative problem solving and internalization. Lack of strategies for seeking social support was associated with loneliness.

• Proceedings of the ESK Conference
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• 1994.04a
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• pp.75-84
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• 1994

A control panel layout method based on the constraint satisfaction problem(CSP) technique was developed to generate an ergonomically sound panel design. This control panel layout method attempts to incorporate a variety of relevant ergonomic principles and design constrains, and generate an optimal or, at least, a "satisfactory" solution through the efficient search algorithm. The problem of seeking an ergonomically sound panel design should be viewed as a multiple criteria problem, and most of the design objectives should be understood as constraints. Hence, a CSP technique was employed in this study for dealing with the multi-constraiants layout problem. The efficient search algorithm using "preprocess" and "look ahead" procedures was developed to handle the vast amount of computational effort. In order to apply the CSP technique to the panel layout procedure, the ergonomic principles such as spatial compatibility, frequency-of- use, importance, functional grouping, and sequence-of-use were formalized as CSP terms. The effectiveness of the developed panel layout method was evaluated by example problems, and the results clearly showed that the generated layouts took various ergonomic design principles into account.esign principles into account.

• Korean Journal of Child Studies
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• v.18 no.2
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• pp.299-310
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• 1997

This study investigated the effects of teacher inquiry methods on children's interpersonal cognitive problem solving ability. The subjects were 40 children who ranged in age from 48 to 60 months. The experimental group participated in problem solving training through teacher's inquiries 3 times per week for 10 weeks, but the control group did not have training in problem solving. The statistical analysis was by the SAS program. The results showed that (1) the group trained in interpersonal problem solving interaction showed a greater frequency for solving interpersonal problems on the post-test; they also employed more ways of solving interaction problems (such as, alternative solutions, consequential solutions, etc.). (2) There was no difference between groups in the levels of responses for solving interpersonal problems.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.439-444
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• 2004

The important problem in high speed spindle is to reduce and minimize the thermal effect by motor and ball bearings. In this study. the effects of bearing preload and cooling for high speed spindle with high frequency motor are investigated. A high speed spindle is composed of angular contact ball bearings, high frequency motor, grease lubrication, oil jacket cooling, and so on. Heat generation of the bearing and the high frequency motor are estimated from the theoretical and experimental data. The thermal analyses of high speed spindle to minimize the thermal effect and maximize the cooling effect are carried out under the various cooling conditions and preload. Method of variable bearing preload and cooling can be useful to design the high speed motor spindle. The results show that the optimal preload and cooling are very effective to minimize the thermal displacement by motor and ball bearing.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.2
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• pp.194-198
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• 2018

The government established the 8th national energy plan that electricity energy from renewables in 2030 will be 20%. The frequency stability problem is one of the key issues to overcome for accomplishing the energy plan. Frequency quality deteriorates due to short term variations of renewables output. Battery energy storage system(BESS) is considered as a good alternative to improve the frequency quality due to its quick response. In this paper, we examined the effectiveness of BESS against the conventional governor properties.

• ETRI Journal
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• v.33 no.1
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• pp.27-31
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• 2011

This paper addresses estimating the frequency of a cisoid in the presence of white Gaussian noise, which has numerous applications in communications, radar, sonar, and instrumentation and measurement. Due to the nonlinear nature of the frequency estimation problem, there is threshold effect, that is, large error estimates or outliers will occur at sufficiently low signal-to-noise ratio (SNR) conditions. Utilizing the ideas of averaging to increase SNR and weighted linear prediction, an optimal frequency estimator with smaller threshold SNR is developed. Computer simulations are included to compare its mean square error performance with that of the maximum likelihood (ML) estimator, improved weighted phase averager, generalized weighted linear predictor, and single weighted sample correlator as well as Cramer-Rao lower bound. In particular, with smaller computational requirement, the proposed estimator can achieve the same threshold and estimation performance of the ML method.