• Journal of Aerospace System Engineering
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• v.11 no.2
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• pp.16-22
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• 2017

This paper investigates fretting wear damage in aerospace, biomedical, and nuclear components. Experimental parameters are identified that affect fretting wear damage. The parameters observed in industries are directly compared. The magnitudes of frequency, relative displacement, and normal force are found to differ depending on the contacting components where fretting wear occurs. In addition, recent solutions to minimize fretting wear damage are reviewed. The solutions include depositing of a low-friction coating, surface treatment, selection of substrate material, and optimal design of contact geometries. This comparative study suggests useful methods and solutions for analyzing fretting wear damage and for designing tribo-components.

• Journal of Korean Academy of Nursing
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• v.38 no.6
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• pp.813-821
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• 2008

Purpose: This study was conducted to develop an instrument measuring awareness of osteoporosis. Methods: The process included construction of a conceptual framework, generation of 86 preliminary items, verification of content validity, selection of secondary items, verification of construct validity and extraction of final items. The 86 items were reviewed for content validity by two groups of experts and were tested to evaluate inter item correlation coefficient by two groups of adult women. From June to August 2007, data were collected from 383 adult women who lived in Seoul and provinces in Korea. Data were analyzed by performing item analysis, Varimax factor analysis and Cronbach's alpha. Results: There were 31 items in the final instrument categorized into 5 factors. The factors were labeled as "preventive behaviors (10 items)", "risk factors (5 items)", "characteristics of osteoporosis (6 items)", "improving bone health (5 items)", and "bone physiology (5 items)". Cumulative percent of variance was 60.92% and eigen values ranged from 1.20 to 12.44. Cronbach's alpha was .948 and ranged from .804 to .917. Conclusion: Validity and reliability of the scale are confirmed in this study showing its utility for measuring awareness of osteoporosis for women. Utilization of the scale will also contribute to designing an appropriate prevention program for osteoporosis.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.1
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• pp.35-40
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• 2015

Generators are the most complex and expensive single element in a power system. The generator protection relays should to minimize damage during fault states and must be designed for maximum reliability. A conventional CDR(Current Differential Relaying) technique based on DFT(Discrete Fourier Transform) filter have the disadvantages that the time information can lead to loss in the process of converting the signal from the time domain to the frequency domain. A WT(Wavelet transform) and WT analysis is known that it is possible with the local analysis of the fault and transient signal. In this paper, to overcome the defects in the DFT process, an application of WT for fault detection of generator is presented. This paper describes an selection of mother Wavelet to detect faults of generator. Using collected data from the fault simulation with ATPdraw, we analyzed the several mother Wavelet through the course of MLD(multi-level decomposition) using MATLAB software. Finally, it can be seen that the proposed technique using detail coefficient of Daubechies level 2 which can be fault discriminant of generator.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.250-261
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• 1999

Based on a set of performance plots relating the design variables to the imposed conditions, an easy-to-use and versatile design procedure for chevron-type multipass plate heat exchangers is developed. In order for the present procedure to cover multipass with unequal passes and non-unity ratio of heat capacity rate, each stream number of transfer unit is adopted as the basic design variable instead of the exchanger number of transfer unit. It is found that there exists a unique relation between the stream and exchanger number of transfer units regardless of the chevron angle and the plate length. In addition, for a given value of the pressure drop the heat transfer area per unit mass flow rate can be expressed in terms of the stream number of transfer unit only. These two relationships in the form of simple plots constitute the framework of design. The sample results in comparison with the available data indicate that the present procedure includes the previous ones as a subset, and that every design method is affected essentially by the selection of specific correlations for the heat transfer coefficient and the friction factor.

• Korean Journal of Child Studies
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• v.16 no.2
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• pp.125-138
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• 1995

The purpose of the present research was to study developmental trends in categorical organization strategy. The subjects were 160 children - 40 nine - year - old boys, 40 nine - year - old girls, 40 seven - year - old boys, 40 seven - year - old girls. All subjects received one of three lists of items differing in category representativeness in either a free -recall or a sort -recall task. The selection of list materials permitted separation of the effects of age differences in category knowledge from those of knowledge per se on children's recall behavior. The tasks were administered to children individually with the memory task followed by the metamemory task. The data was analyzed with three - way ANOVA arid Pearson's correlation coefficient. The results were that (1) Children's recall, clustering, and metamemory increased with age, while age effects for clustering were restricted to the sort - recall/high typicality condition. At each age level, children showed higher level of recall, clustering and metamemory for category typical rather than atypical list, and sort - recall than free-recall. Level of clustering and metamemory were superior in the sort - recall task and for items of high category typicality. (2) 9 - year - old children were capable of deliberately and efficiently using category organization as a memory strategy at least when appropriate contextual support was present (as determined by task requirements and list materials: sort - recall/high typicality).

• Convergence Security Journal
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• v.12 no.3
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• pp.115-121
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• 2012

Software failure time presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing. For data analysis of software reliability model, data scale tools of trend analysis are developed. The methods of trend analysis are arithmetic mean test and Laplace trend test. Trend analysis only offers information of outline content. In this paper, we discuss forecasting failure time case of failure time censoring. In this study, we predict the future failure time by using the curve regression analysis where the s-curve, growth, and Logistic model is used. The proposed prediction method analysis used failure time for the prediction of this model. Model selection using the coefficient of determination and the mean square error were presented for effective comparison.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.8
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• pp.506-509
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• 2003

This paper describes the possibility of analyzing gait pattern from the changes of the lower leg electrical impedance. This impedance was measured by the four-electrode method. Two current electrodes were applied to the thigh, knee, and foot., and two potential electrodes were applied to the lateral, medial, and posterior position of human leg. The correlation coefficients of the joint angle and the impedance change from human leg movement was obtained using a electrogoniometer and 4ch impedance measurement system developed in this study. We found the optimal electrode position for knee and ankle joint movements based on high correlation coefficient, least interference, and maximum magnitude of impedance change. The correlation coefficients of the ankle, knee, and the hip movements were -0.913, 0.984 and 0.823, respectively. From such features of the human leg impedance, it has been made clear that different movement patterns exhibit different impedance patterns and impedance level. This system showed feasibility that lower leg movement could be easily measured by impedance measurement system with a few skin-electrodes.

• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.33-38
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• 2013

Many occupational workers or professionals have to walk on the various floors for a long period of time. The objective of this study was to develop the safety shoes with increased traction through the material selection. In order to fulfill our objective, first, two kinds of filler were selected to compare the wear mechanism at outsole surface. The developed rubber materials were tested with two kinds of portable slip meters. The sample safety shoes with developed rubber materials were also tested with subject in the laboratory. During walking, the safety shoes were naturally abraded with counter surface. The coefficient of friction(COF) was gradually decreased with number of steps to 30,000, while the COF was abruptly increased from 30,000 to 40,000. The experimental results showed that COF tested with silica rubber was at least 10% higher than that with carbon black rubber in wet or detergent condition. It has been well recognized that filler properties play a important role in wet traction in the tire industry. However it has been unclear that filler properties would be decisive factor in safety shoes. Our study shows that silica exhibits a higher slip resistance than carbon black without reference to wear states in wet or detergent condition. So, this results will provide guides for outsole compounders to develop new products and improve product performance.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.21 no.1
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• pp.92-96
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• 1976

Considerably large phenotypic and genotypic variations for the important agronomic traits were found in a soybean population consisted with 825 local lines collected in Korea. Genetic coefficient of variation, heritability, and genetic gain for seed weight, plant height. and number of pods per plant were relatively high. Maturity showed a high heritability value with a low genetic gain and the result may be due to the narrow range of maturity date of the population studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.162-172
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• 1998

A numerical study of premixed combustion within a porous ceramic burner (PCB) is performed to understand flame behavior with respect to various model parameters. Basic flame structure within the porous ceramic burner and species profiles such as NO and CO are examined. Sensitivity analysis of flame speed, gas and solid temperature, NO and CO emission from the burner with respect to reaction steps and various physical properties of the ceramic material is applied to find the most significant parameters in selection of porous materials for the porous ceramic burner. Effects of thermal conductivity, extinction coefficient and scattering albedo on the burner characteristics are studied through the sensitivity analysis. The results of sensitivity study reveal the order of importance in ceramic material properties to get suitable burner performance. Scattering albedo, which governs the ratio of absorbed energy by the ceramic material to total radiative energy transferred, is one of the most important parameters in the material properties since it affects the actual absorbed radiation rate and thus it largely affects the flame structure. Through the study, it is found that the sensitivity study can be used to estimate the flame behavior within the porous ceramic burner more effectively.