• Nuclear Engineering and Technology
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• 제39권2호
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• pp.133-142
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• 2007

The Electric Power Research Institute (EPRI) demonstrated a method for monitoring the performance of instrument channels in Topical Report (TR) 104965, 'On-Line Monitoring of Instrument Channel Performance.' This paper presents the results of several models originally developed by EPRI to monitor three nuclear plant sensor sets: Pressurizer Level, Reactor Protection System (RPS) Loop A, and Reactor Coolant System (RCS) Loop A Steam Generator (SG) Level. The sensor sets investigated include one redundant sensor model and two non-redundant sensor models. Each model employs an Auto-Associative Kernel Regression (AAKR) model architecture to predict correct sensor behavior. Performance of each of the developed models is evaluated using four metrics: accuracy, auto-sensitivity, cross-sensitivity, and newly developed Error Uncertainty Limit Monitoring (EULM) detectability. The uncertainty estimate for each model is also calculated through two methods: analytic formulas and Monte Carlo estimation. The uncertainty estimates are verified by calculating confidence interval coverages to assure that 95% of the measured data fall within the confidence intervals. The model performance evaluation identified the Pressurizer Level model as acceptable for on-line monitoring (OLM) implementation. The other two models, RPS Loop A and RCS Loop A SG Level, highlight two common problems that occur in model development and evaluation, namely faulty data and poor signal selection

• Journal of Satellite, Information and Communications
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• 제11권4호
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• pp.52-57
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• 2016

The backscatter signals are very weak so they can be easily interfered by signal interferences and channels. In this paper, we propose a two-level classification algorithm for backscatter communications which chooses the idle frequency channel based on cognitive radio systems. The two-level classification algorithm provides an optimal idle frequency channel by obtaining informations about idle frequencies, fading of the channels, and the channels' usage state by primary users. Our simulation results show the improvement of BER and received power performance in backscatter communications by using the proposed algorithm, and the improvement of the algorithm's performance in backscatter communications.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제19권2호
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• pp.213-219
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• 2006

Topology optimization problem requires numerous repeated evaluations of objective function and design sensitivity for elements within design domain with various density distributions. The recently proposed two-level condensation scheme(TLCS) is very promising for the construction of reduced system and for an accurate and efficient analysis concerned about eigenvalue and dynamic problems. We used the two-level dynamic condensation scheme for the analysis and sensitivity computation part in the structural topology optimization problem. The results of the topology optimization for the reduced system show the TLCS provides high accuracy and computation efficiency compared to the full scale system within engineering accuracy.

• Transactions of the Korean Society of Mechanical Engineers
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• 제12권4호
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• pp.790-805
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• 1988

Static strength and fatigue life scattering of glass fiber reinforced epoxy composite materials has been studied. Normal, lognormal, two-parameter and three-parameter Weibull distribution functions are used for strength and one-stress fatigue life distribution. The value of mean fatigue life is analysed using mean fatigue life, mean log fatigue life and expected value of 2 and 3-parameter Weibull distribution functions. Modification on non-statistical cumulative damage models is made in order to interpret the result of two-stress level fatigue life scattering. The comparison results show that 3-parameter Weibull distribution has better predictions in static strength and one-stress level fatigue life distributions. However, no advantage of 3-parameter Weibll distribution is found over 2-parameter Weibull distribution in two-stress level fatigue life predictions. It is found that two-stress level fatigue life prediction by the expanded equal rank assumption is close to the experimental data.

• The Korean Journal of Applied Statistics
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• 제19권1호
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• pp.111-120
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• 2006

In a two-stage two-level balanced nested design, type I error rates for the parametric tests and the rank transformed tests for the main effects and the nested effects are in overall similar to each other. Furthermore, powers for the rank transformed statistic for the main effects and the nested effects in a two-stage two-level balanced nested design are generally superior to powers for the parametric statistic When the effect size and the sample size are increased, we can find that powers increase for the parametric statistic and the rank transformed statistic are dramatically improved. Especially for the case of the fixed effects in the asymmetric distributions such as an exponential distribution, powers for the rank transformed tests are quite high rather than powers for the parametric tests.

• Journal of the Ergonomics Society of Korea
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• 제32권6호
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• pp.529-534
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• 2013

Objective: This study determines which of two types of 2D menu is better on iPhone. Background: Menu systems have been important components in modern graphical user interfaces. Review of menu design studies for human-computer interaction suggests that menu design guidelines for smartphones need to be reappraised. Method: A nested factorial design was used. Twenty-four participants were divided into two groups. The subjects were nested within the menu type. Two types of menus are an overview menu and a text menu. Two different breadth levels are 16 and 64. The participants performed five tasks in each breadth level. A task is defined as locating a product or product class on the deepest level of the hierarchy. An Apple iPhone 2G was used. Results: The results for ANOVA indicated a lack of a significant difference for time to respond between the two types of 2D menus. The overview menu showed the better satisfaction score between the two menu types. Conclusion: Even though the differences were not significant, an overview menu tended to show better performance and preference scores than a text menu that required scrolling. Application: This study can provide menu design guidelines when 2D menus are considered for small displays in a high breadth level.

• Journal of Nutrition and Health
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• 제29권5호
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• pp.528-532
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• 1996

The purpose of this study was to analyse copper intake and effect ofZn(30mg ZnSO4/d) supplementation on plasma copper level of Korean adults. Daily Cu intakes were studied in ninety subjects aging 20-20 years. Among them twenty four subjects participated in 6 weeks Zn supplementation study. The men consumed 1.47($\pm$0.64)mg of Cu and the women consumed 0.98($\pm$0.43)mg of Cu daily. the most abundant sources of Cu was meat, fish, egg and soybean group, the second was cereal and grain group and the third was vegetable group. These three groups supplied about 90% of copper in the subjects. The plasma copper level of the subjects was not changed much until two weeks of Zn supplementation. However, after two weeks of Zn supplementation plasma copper level was reduced continuously during the experiment. There was no significant difference in plasma Cu level between control and supplement group of the men, while the supplemented women showed significantly lower plasma Cu level than control group at week 4(p<0.01) and week 6(p<0.05). Although plasma Cu level of the subjects was slightly changed, its concentration in plasma was still in normal range in all groups and no one showed clinical Cu deficiency. Therefore the Zn supplementation of RDA level doesn't seem to cause any adverse effect on Cu status.

• Journal of Korean Public Health Nursing
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• 제21권1호
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• pp.75-84
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• 2007

Purpose: The purpose of this study was to investigate the state and factors associated with level of physical activity and exercise in adolescents. Method: The subjects in this study included 528 adolescents registered at two junior high schools and two senior high schools in J City. The data were collected between October 20 and 30, 2006. Result: The study results showed that 23.8% of the adolescents engaged in vigorous activities for at least 20 minutes, three times a week, while 3.8% of the adolescents participated in moderate activities for at least 30 minutes, five times a week. The subjective level of health was determined to be $3.51\pm.91$ points on a 5-point scale. The level of stress was $2.58\pm.83$ points on a 4-point scale. The obesity index was $4.26\pm20.84$ points. Significant correlations were found between the subjective level of health and level of stress (r=-.201, p=.000), the subjective level of health and the obesity index (r=-.135, p=.004), and between the level of stress and the obesity index (r=.107, p=.024). Conclusion: These results showed that developing a health promotion program that includes an exercise program specific to gender and level of education, individualized strategies of stress control and optimal weight control is required.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 한국경영과학회 1998년도 추계학술대회 논문집
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• pp.224-227
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• 1998

This paper proposes inter-level causal reasoning to implement synergistic approach. We decompose KOSPI prediction model into economy and industry level. Two kinds of intra-level QCOM are combined in inter-level QCOM via Inter-level relations. Downward reasoning is achieved by propagating the disturbance in the higher level to lower level while upward reasoning is to analyze the reverse cases.

• Atmosphere
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• 제31권1호
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• pp.29-43
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• 2021

In this study, two-step statistical approach including Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) was employed, and main meteorological factors explaining the high-PM2.5 episodes were identified in two regions: Seoul and Busan. We first performed PCA to isolate the Principal Component (PC) that is linear combination of the meteorological variables observed at two levels: surface and 850 hPa level. The employed variables at surface are: temperature (T2m), wind speed, sea level pressure, south-north and west-east wind component and those at 850 hPa upper level variables are: south-north (v850) and west-east (u850) wind component and vertical stability. Secondly we carried out MLR analysis and verified the relationships between PM2.5 daily mean concentration and meteorological PCs. Our two-step statistical approach revealed that in Seoul, dominant factors for influencing the high PM2.5 days are mainly composed of upper wind characteristics in winter including positive u850 and negative v850, indicating that continental (or Siberian) anticyclone had a strong influence. In Busan, however, the dominant factors in explanaining in high PM2.5 concentrations were associated with high T2m and negative u850 in summer. This is suggesting that marine anticyclone had a considerable effect on Busan's high PM2.5 with high temperature which is relevant to the vigorous photochemical secondary generation. Our results of both differences and similarities between two regions derived from only statistical approaches imply the high-PM2.5 episodes in Korea show their own unique characteristics and seasonality which are mostly explainable by two layer (surface and upper) mesoscale meteorological variables.