• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.137-147
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• 2006

In this study, shape memory alloy damper with characteristics of pseudoelastic hysteresis for helicopter rotor blades are investigated. SMAs can be available in damping augmentation of vibrating structures. SMAs show large hysteresis in the process of pseudoelastic austenite-martensite phase transformation which takes place while subjected to loading above the austenite finish temperature. Since SMAs display pseudoelastic hysteresis behavior over large strain ranges, a significant amount of energy dissipation is possible. A damper can be designed with SMA wires prestressed to a baseline level somewhere in the middle of the pseudoelastic stress range. An experimental study of the effects of pre-strain and cyclic strain amplitude as well as frequency on the damping behavior of pseudoelastic shape memory alloy wires are performed. The effects of the shape memory alloy damper on aeroelastic and ground resonance stability of helicopter are studied. In aeroelastic stability, the dynamic characteristics of blades related to pitch angle and the amplitude of lag motion for the rotor equipped with SMA damper were examined. The performance of SMA damper on ground resonance instability are presented through the frequencies and modal damping with respect to rotating speed.

• Ocean and Polar Research
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• v.30 no.3
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• pp.313-324
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• 2008

In order to understand the variation of ENSO-related oceanic environments in the tropical and North Pacific Ocean, spatio-temporal variations of sea surface temperature anomaly (SSTA) and sea surface height anomaly (SSHA) are analyzed from distributions of complex empirical orthogonal functions (CEOF). Correlations among warm pool variation, southern oscillation index, and ocean surface currents were also examined with respect to interannual variability of the warm pool in western tropical Pacific. Spatio-temporal distributions of the first CEOF modes for SSTA and SSHA indicate that their variabilities are associated with ENSO events, which have a variance over 30% in the North Pacific. The primary reasons for their variabilities are different; SST is predominantly influenced by the change of barrier layer thickness, while SSH fluctuates with the same phase as propagation of an ENSO episode in the zonal direction. Horizontal boundary of warm pool area, which normally centered around $149^{\circ}E$ in the tropics, seemed to be expanded to the middle and eastern tropical regions by strong zonal currents through the mature phase of an ENSO episode.

• Child Health Nursing Research
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• v.13 no.3
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• pp.318-328
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• 2007

Purpose: Because it is important to prevent adolescents from becoming involved in smoking, this study was done to explore important factors influencing cigarette use and the increase in smoking frequency. Method: For this study the Korea Youth Panel Survey (KYPS) was analyzed. Because the KYPS is longitudinal, a fixed effect regression method was used to control for the effects of time-independent factors. More specifically, a logistic regression was used to explore factors affecting cigarette use, and a Poisson regression was used to explore smoking frequency. Result: As the adolescents got older, the number of male adolescents who tried smoking increased, while the number of female adolescents who tried smoking decreased. Also, the frequency of cigarette use among male and female smokers increased over time. Significant factors affecting cigarette use were friends who smoked, delinquent behavior, and loneliness at schools. Important factors affecting the increase in smoking frequency were grade (e.g., the 2nd- and 3rd-year of middle school), friends who smoked, delinquent behavior, monthly pocket money, expectation for the highest level of education, and attack tendency. Conclusions: To solve the problems linked to adolescent smoking, it is critical to develop intervention programs that target specific homogeneous subgroups of smokers, and that take into consideration gender difference in smoking and factors affecting levels of smoking behavior.

• Journal of Korean Association for Spatial Structures
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• v.3 no.1 s.7
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• pp.87-97
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• 2003

The structural system that discreterized from continuous shells is frequently used to make a large space structures. As well these structures show the unstable phenomena when a load level over the limit load, and snap-through and bifurcation are most well known of it. For the collapse mechanism, rise-span ratio, element stiffness and load mode are main factor, which it give an effect to unstable behavior. In our real situation, most structures have semi-rigid joint that has middle characteristic between pin and rigid joint. So the knowledge of semi-rigid joint is very important problem of stable large space structure. And the instability phenemena of framed space structures show a strong non-linearity and very sensitive behavior according to the joint rigidity For this reason In this study, we are investigating to unstable problem of framed structure with semi-rigidity and to grasp the nonlinear instability behavior that make the fundamental collapse mechanism of the large space frame structures with semi-rigid joint, by proposed the numerical analysis method. Using the incremental stiffness matrix in chapter 2, we study instability of space structures.

• Agribusiness and Information Management
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• v.8 no.2
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• pp.16-21
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• 2016

The interest in convenience food has increased over the years. Many researchers have tried to discover what factors affect the consumption of convenience food. Despite the diversity of studies, few studies emphasize a household's income. The aim of this article is to identify the different consumption patterns between upper, middle, and lower income brackets. Generally, households with higher income consumed more convenience food or the relationship was not significant. However, many convenience foods are regarded as nutritionally unbalanced and have a lower quality. So, the hypothesis cannot be easily confirmed because there are tradeoffs not only between health, as nutrition balance and cost, but also health and convenience. Thus, there is a need to indicate the divergent attributes of buying convenience food in a distinct income group. In addition, the convenience food is subdivided into two distinct categories: convenience food as a substitution for a whole meal (unhealthy) and substitution as part of a diet (healthy). We found that higher income groups purchase healthier convenience food while lower income groups purchase unhealthier convenience food. Also there are distinct attributes that influence the consumption of healthy and unhealthy convenience food.

• Asian Oncology Nursing
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• v.12 no.1
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• pp.52-60
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• 2012

Purpose: This study is to determine knowledge about early detection and risk perception of cancer according to taking cancer screening tests in the general population. Methods: The participants were 151 people aged 40 years or older. A questionnaire consisted of knowledge about early detection (warning signs, cancer screening methods, general knowledge for early detection), cancer risk perception and history of cancer screening during past 2 years. Results: The percentages of correct answers were 64.7% in knowledge about warning signs, 73.7% in knowledge of cancer screening tests and 80.1% in general knowledge for early detection. Participants had the highest knowledge about screening methods for stomach cancer and the lowest for liver and colon cancer. The level of risk perception was medium. The participants who participated in cancer screening showed lower risk perception than those who did not. There was no significant relationship between knowledge and performance of cancer screening. The primary reason for not participating in cancer screening was patient's perception of their own health. Conclusion: These results suggest that cancer risk perception can affect the performance of cancer screening and we need to study how to handle this problem. Additionally screening programs should focus on liver cancer and colon cancer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.123-129
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• 2017

This study investigated the dental prosthesis condition from the sixth primitive data of Korea National Health and Nutrition Examination Survey to analyze and compare the necessity of existent dental prosthesis condition, dental bridge and dentures in order to determine the real oral health condition by educational level targeting adults aged over 20 years old. From the results, based on demographic-sociologic features, 32.2% of females were under elementary school graduation level, which was lower than males, and the educational level decreased with increasing age, and these trends were statistically significant. As for income level, 45.3% of university graduates had the highest income level and 77.4% of this age group were professionals, which was the highest percentage and was statistically significant. In terms of dental prosthesis condition according to educational level, the under elementary school graduation group had the most dental prosthesis and the greatest need for partial dentures and full dentures. As for the necessary number of fixed implants, the upper jaw had the most number of fixed implants and in the lower jaw, the under middle school graduation needed the most fixed implants.

• Journal of Korean Academy of Nursing
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• v.37 no.1
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• pp.35-43
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• 2007

Purpose: This study was to explore the prevalence of alcohol experiences and to identify the expectancy on the effects of alcohol and alcohol knowledge in early adolescents. Method: The cross-sectional survey of 1854 students from seven middle schools in one district of Seoul was conducted by convenience sampling. Alcohol experience and early onset of alcohol use were measured by the Youth Risk Behavior Survey. Alcohol expectancy was measured by an Alcohol Effects Questionnaire. Result: Over sixty five percent of adolescents reported that they had previous drinking experiences. The participants with no alcohol drinking experience had a lower level of alcohol knowledge than those with experience(t=2.73, p=.007). In expectancy on effects of alcohol, girls had a more positive alcohol expectation than boys(t=-2.54, p=.011). Alcohol knowledge negatively correlated with alcohol expectancy(r=-.40 p=.000). In regression of alcohol expectancy, gender and alcohol knowledge were significant predictors explaining 17%. Conclusion: The results support that alcohol expectancy is an important link with early drinking experiences and alcohol knowledge, focusing on the importance of gender differences. Therefore, an alcohol prevention program in early adolescence is needed and should be focused on multidimensionality of the alcohol expectancy with developmental and psychosocial factors for early adolescents.

• Research in Community and Public Health Nursing
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• v.17 no.3
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• pp.376-386
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• 2006

Purpose: This study was conducted to analyze the exposure of female high school students to Internet pornography and its related factors. Methods: A total of 392 female high school students were selected through convenience sampling. Data were collected using self-reported questionnaires from June 27 to July 8, 2005. Results: 1. As for exposure to Internet pornography, 61.0% of the respondents had been exposed to Internet pornography and 29.7% had their first exposure to Internet pornography when they were in the 3rd grade of middle school. In addition, 87.9% of the respondents spent less than 30 minutes each time to view Internet pornography. In 41.8% of the respondents, the reason for seeing Internet pornography was curiosity about sexuality. 2. Both the level of sexual knowledge (t=3.174, p=.002) and attitude (t=2.567, p=.011) were significantly different between the exposure group and the non-exposure group. 3. Grade, daily mean time to use computer, and sexual knowledge had statistically significant effects on exposure to Internet pornography. Conclusion: It is necessary to make repeated study to find other variables that affect students' exposure to Internet pornography and to develop education programs to enhance students' coping ability against Internet pornography. Also, parents' concern over youth is necessary to prevent them from being exposed to Internet pornography.

• Research in Mathematical Education
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• v.7 no.3
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• pp.163-189
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• 2003

The purpose of this study is to develop a test, which can be used in creative problem solving ability in mathematics of the mathematically gifted and the regular students. This test tool is composed of three categories; fluency (number of responses), flexibility (number of different kinds of responses), and originality (degree of uniqueness of responses) which are the factors of the creativity. After applying to 462 middle school students, this test was analyzed into item analysis. As a results of item analysis, it turned out to be meaningful (reliability: 0.80, validity: item 1(1.05), item 2(1.10), item 3(0.85), item 4(0.90), item 5(1.08), item difficulty: item 1(-0.22), item 2(-0.41), item 3(0.23), item 4(0.40), item 5(-0.01), item discriminating power: item 1(0.73), item 2(0.73), item 3(0.67), item 4(0.51), item 5(0.56), over the level of a standard basis. This means that the test tool was useful in the test process of creative problem solving ability in mathematics