• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.88-93
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• 1998

Since rattling noise, which occur in mechanical linkage with free play or glove boxes in passenger cars, play an important role in the generation of industrial noise and vibration, it is interest to study these dynamics. A difference equations are derived which described the motions of a mass constrained by pre-compressed spring and forced by a high frequency base excitation. Two types of saddle are founded from these difference equations and the stable and unstable manifolds are constructed in these saddle point. For a certain region in a parameter space of exciting displacement and coefficient of restitution, transversal intersections of stable and unstable manifolds exist. Therefore it is founded that there are large families of periodic and irregular non-periodic motions in rattling system i.e. chaos motion is observed.

• Journal of the Korea Fashion and Costume Design Association
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• v.25 no.2
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• pp.1-16
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• 2023

Due to the current seriousness of environmental pollution and the eco-friendly movement of the fashion industry, research on sustainable fashion design is being actively conducted. In this study, consumer perception of upcycling products, are divided into image, function, and meaning; and image is further divided into shape, color, and material. It was redefined as pattern, and image recognition was evaluated among men and women in their 20s and 30s, and men and women in their 40s and 50s used as subjects. First, factors that determine each image were extracted based on qualitative analysis of the precedent cases of upcycling bags, and quantitative analysis of the subjects was induced through a questionnaire. As a result of the analysis of evaluation items related to image association, the average frequency analysis of all subjects for each stimuli and the cognitive variance of the frequency analysis by generation by gender were found to be similar. However, awareness of some stimuli by generation showed a significant difference. Overall, in the three stimuli with high overall preference, common features, such as the basic box-shaped symmetrical structure, the monochromatic color of the Munsell system, solid and practical texture, and appropriate use of patterns were identified. In addition, it was confirmed that there was a difference with factors such as femininity, simplicity, touch, and splendor in the measurement factors. In conclusion, it is considered that the main significance of this study is that it excluded the recognition and meaning of upcycling products and explored the original design and image elements of products. Therefore, it is expected that this study will be used as a basic data for responding to the gender image of each generation as an alternative method of sustainable fashion design, and it will be an opportunity to expand the scope of the study to a detailed study beyond the biased topic.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.190-192
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• 2003

When generators trip on the occurrence of disturbance, the power system frequency declines by the amount of difference between demand and supply due to the imbalance between power generation and load. Even though the power system is operated with the same grid structure, generating capacity, and load, the resulting frequency decline and its recovery slope show different aspects according to the inertia constants of generators, spinning reserves, and the speed adjusting rates at the governors. From this point of view, we analysed differences of frequency decline at the various conditions in domestic power system.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.1
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• pp.82-92
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• 1997

The purpose of this study is to segment an infant's wear market on the base of housewife's fashion life-style for satisfaction of varied needs and high efficiency of marketing activity. This study was used 183 questionnaires (20∼30 generation housewife in Seoul) for statistical analysis. This study was used factor analysis and cluster analysis to group same respondents and frequency analysis, x2_analysis, ANOVA, duncan-test to analyze characteristics of demographics, clothing purchase pattern for each segmented group. The respondents were divided into 4 groups of differnt housewife's fashion life-style matte tons according to the results of analysis. The findings of the research on each groups are summarized as follows: 1) Subdividing market was classified such as a fashion-seeking/shoping-oriented group, personality-seeking group, practical/planning group, traditional conservative group. 2) According to characteristics of demographics in Subdividing market, there were significant difference in their school career, family monthly income, existence of job. 3) According to clothing purchase pattern in Subdividing market, there were significant difference in housewife's fashion life-style. But there were only partly significant difference in characteristics of demographics. In this study, housewife's fashion life-style segmentation in infant's wear market has purpose that marketing managers are given these infornations and various wants of consumers can be satisfied.

• Journal of Community Nutrition
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• v.5 no.2
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• pp.93-104
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• 2003

Although a generation-related difference in nutrient and food-group intake has been broadly recognized in the Japanese population, few studies have examined the difference and correlation of intakes with consideration of a family line and co-habitation status. We conducted a dietary survey using female college students in dietetic course in Aichi, Japan, and their mothers and grandmothers. A validated self-administered diet history questionnaire was used for assessment of intakes. Data from 110 families were included in the analysis. The means of 13 nutrients and 10 food groups (of the 15 and 14, respectively) showed significant differences among the three generations. A significant difference was observed in the carbohydrate, protein, saturated fatty acid, cholesterol, and fish intakes between the students living with their mothers and those apart. In the correlation analyses between generations, moderate correlation was observed for most nutrients and food groups between the students and their mothers living together (correlation range = 0.30-0.61 for nutrients, and = 0.21 -0.56 for food groups). A wide variation with no consistency was observed for the correlation between the students and their grandmothers (-0.18 -0.59 and -0.33 -0.65, respectively), No meaningful correlation was observed between any two generations living apart. Among the food groups examined, pulses, fish, and vegetables showed relatively large differences for the correlation between two groups with different living conditions. When living together, the correlation coefficients for nutrients and food groups between the students and their mothers decreased according to the increase in frequency of eating out by the students. These results suggest that living together and eating together were an important factor for the resemblance in dietary habits between generations in the population with a marked generation-related difference in intakes. (J Community Nutrition 5(2) : 93-104, 2003)

• Culinary science and hospitality research
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• v.16 no.4
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• pp.1-14
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• 2010

This study is to analyze the difference of perception about Korean traditional food by generations in Busan area. For the analysis of this study, both the cross tabulation analysis and Frequency analysis were used, by choosing the random specimen of investigation from middle and high school students, college students and general people residing in Busan area. The result of the study is as follows. First, the frequency of preference for traditional food is different by generations. Second, Korean traditional food is the most preferred among all generations. Third, menu is decided mainly for a father in the family. Finally, standardized and simplified recipes are needed for busy people. To improve the difference by generation, herbs or seasonings should be added or ingredients should be changed into ones suitable to young generation's taste. It is necessary for future studies to have extended samples nationwide for balanced specimen.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.82-86
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• 2002

The thermal characteristics of high-speed air spindle system with built-in motor are studied. Experiment and finite difference method analysis obtain temperature rise and temperature distribution of housing. For the analysis, air fluid film model is built and temperature rise and distribution in thermal steady state are computed for each rotational speed. Generally, it is said that the heat generation of air bearing is negligible. But the heat generation in air film by heat dissipation can not be negligible especially into high-speed region of the journal. In case that the heat generation of air spindle system is high, natural frequency of the spindle system becomes lower when the thermal state is in steady-state and it means the changes of air bearing stiffness due to the change of bearing clearance. It is shown that the temperature rise of air spindle system causes thermal expansion and induces the variation of bearing clearance. In consequence the stiffness of air bearing becomes smaller.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.4
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• pp.120-127
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• 2006

An experimental study was carried out in order to investigate the effects on the fore- and hind-wings of a dragonfly-type model. A model with two pairs of wing was developed to measure the lift and thrust of a dragonfly-type model. The fore-wing and hind-wing had incidences angle of $0^{\circ}\;and\;10^{\circ}$. The freestream velocity is 1.6m/sec and the corresponding chord Reynolds number was $Re=2.88{\times}10^3$. Also, these experiments were carried out with a phase difference of $90^{\circ}$ between the fore- and hind-wing, aerodynamic forces caused by fore-wing only and two pairs of wings were investigated according to the reduced frequency. The results show that the model with fore-wings only generates a thrust component; however, the dragonfly-type model with hind-wings with an incidence angle of $10^{\circ}$ generates a drag component. The total drag is also increased with reduced frequency due to the increased lift of hind-wings.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.113-118
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• 2004

This paper presents a two-dimensional edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle by the finite difference lattice Boltzmann method (FDLBM). We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted coordinates. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of $\alpha=23^0$. At a stand-off distance $\omega$, the edge is inserted along the centreline of the jet, and a sinuous instability wave with real frequency f is assumed to be created in the vicinity of the nozzle and th propagate towards the downstream. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. Its interaction with the wedge produces an irrotational feedback field which, near the nozzle exit, is a periodic transverse flow producing the singularities at the nozzle lips. The lattice BGK model for compressible fluids is shown to be one of powerful tool for computing sound generation and propagation for a wide range of flows.

• ETRI Journal
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• v.29 no.6
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• pp.725-735
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• 2007

This paper describes a line element planar antenna with three frequency bands. To obtain broadband characteristics, a modified planar antenna that has semi-elliptical elements based on the characteristics of a line element planar antenna is proposed and analyzed by the finite difference time domain method. Return loss characteristics are discussed as functions of the eccentricity values of semi-ellipse at each element. The broadbanding of the modified planar antenna is implemented based on the results. The planar antenna with three systems (an 800 MHz band cellular phone, a third-generation cellular phone, and a 2.4 GHz band wireless LAN system) is considered as an application example.