• KIPS Transactions on Computer and Communication Systems
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• v.2 no.12
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• pp.533-540
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• 2013

Anonymity is the one of main reasons for substantial improvement of Internet. It encourages various users to express their opinion freely and helps Internet based distributed systems vitalize. But, anonymity can cause unexpected threats because personal information of an online user is hidden. Especially, distributed systems are threatened by Sybil attack, where one malicious user creates and manages multiple fake online identities. To prevent Sybil attack, the traditional solutions include increasing the complexity of identity generation and mapping online identities to real-world identities. But, even though the high complexity of identity generation increases the generation cost of Sybil identities, eventually they are generated and there is no further way to suppress their activity. Also, the mapping between online identities and real identities may cause high possibility of losing anonymity. Recently, some methods using online social network to prevent Sybil attack are researched. In this paper, a new method is proposed for extracting a user's system-wide Sybil-resistant trust value by using the properties embedded in online social network graphs. The proposed method can be categorized into 3 types based on sampling and decision strategies. By using graphs sampled from Facebook, the performance of the 3 types of the proposed method is evaluated. Moreover, the impact of Sybil attack on nodes with different characteristics is evaluated in order to understand the behavior of Sybil attack.

• Journal of Korea Water Resources Association
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• v.52 no.spc2
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• pp.801-810
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• 2019

This study analyzes the impact on geomorphic changes downstream due to alternate bars developed weir upstream through laboratory experiments. The disturbance, such as a spur in the side wall, of the flow at the inlet of the channel triggers the development of alternate bar upstream at the beginning of the experiment, and gradually moved downstream with keeping their shapes over time. The bed in the downstream of weir in the mid of channel scoured due to the scarcity of sediment inflow because weir upstream traps it. Moreover, bar migration speed decreases as the bars approaches to the weir with time. However, as time increases, the alternate bars upstream migrate over the weir, and sediment in the eroded bed of the weir downstream are deposited. The phase of the bar upstream changes oppositely after passing through the weir. The phase of the bar downstream changes rapidly as the shape of alternate bar is clear upstream, which is affected by the strong disturbance. The phase of bar changes, and the bar migration speed decreases gradually with time, and finally stopped due to forcing effects on the bar by the disturbance. The faster the reaction of alternate bar with a long spur, the larger the bar height formed downstream and the shorter the bar length. This means that the larger the forcing effect of bar, the more it affects the bar migration. In addition, although the size of the alternate bar increases over time, the bar doesn't migrate downstream and a forced bar is generated.

• Journal of Navigation and Port Research
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• v.45 no.4
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• pp.224-230
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• 2021

It has been 16 years since the government announced its first Ocean Education Policy in 2005. Although the public consensus on the importance of ocean education has been formed, it is impossible to objectively analyze the impact of the policy on the society or the economy. The aim of this paper was to identify differences in perceptions and behaviors about the ocean between groups participating in ocean education and non-participating groups and to analyze the effectiveness of ocean education by developing measurement indicators for the value that individuals gave to ocean education services. To conduct this study, first, the value of ocean education was defined and value items that could be provided to individuals were classified. Second, to develop indicators that could measure classified value items, a Delphi survey was conducted to collect opinions of various experts. Third, by measuring the content validity ratio (CVR) for each item, final indicators and questionnaire were derived. As a result of Delphi analysis, 18 items with a CVR value of 0.6 or higher were finally adopted out of 32 indicator items. In the cognitive value category, indicators that could identify an individual's level of knowledge of the ocean, change in perception, and problem-solving ability were selected. In the behavioral value category, indicators were expanded to judge changes in attitudes and relationships toward the ocean and responsible behavior in more detail. This study is meaningful in that it provides the basis for directly judging the value of ocean education service provided by the government to the people. Results of such analysis are expected to contribute to securing a stable budget and the justification for expanding human resources in the government's continuous promotion of ocean education policies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.552-561
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• 2019

The purpose of this study was to verify a model for the structural relationships of safety education provided by a marine leisure sports experience center to first-aid coping skills and experience satisfaction. 307 male and female customers who used a marine leisure sports experience center located in the city of S-si, K-do Province, were investigated from June 15 to August 30, 2017. The collected data were statistically analyzed by SPSS/PC+ 20.0 and Amos 16.0. The findings of the study were as follows: First, the safety education offered by the marine leisure sports experience center was found to have affected first-aid coping skills(t=3.425, p<.001). Second, the safety education by the marine leisure sports experience center was found to have exerted an influence on experience satisfaction(t=3.751, p<.001). Third, the first-aid coping skills of the marine leisure sports experience center was found to have had an impact on experience satisfaction(t=6.781, p<.001). The measurement model for the hypothesis test in this study was found to be appropriate(GFI=.978, NFI=993, CFI=984). Given the findings of the study, more extended safety education is expected to be effective, as customers who use marine leisure sports experience centers will be able to enjoy marine leisure sports more safely and improve their quality of life when they are compulsorily required to receive safety education.

• Clean Technology
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• v.24 no.4
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• pp.293-300
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• 2018

Sulfamethoxazole (SMX) is sulfaamide-based synthetic antibiotics, which are widely prescribed pharmaceutical compound to treat bacterial infections in both human and animals. Most of them are not completely decomposed as refractory substances. The environmental impact of pharmaceuticals as emerging contaminants has generated severe concerns. In this study, catalytic wet peroxide oxidation (CWPO) of SMX was carried out with $Cu/Al_2O_3$ catalyst and investigated the optimum reaction conditions of temperature, dosage of catalyst and concentration of $H_2O_2$ to completely decompose the SMX. It was observed that SMX was completely decomposed within 20 min using 0.79 mM $H_2O_2$ and 6 g $Cu/Al_2O_3$ catalyst at 1 atm and $40^{\circ}C$, but SMX was not fully mineralized and converted to intermediates as hydroylated-SMX, sulfanilic acid, 4-aminobenzenesulfinic acid and nitrobenzene. After that these are completely mineralized through organic acid. We proposed the decomposition reaction path ways of SMX by analyzing the behavior of these intermediates. To investigate the durability of heterogeneous catalyst, decomposition of SMX was observed by continuously recycling catalysts. When the heterogeneous catalyst of 10 wt% $Cu/Al_2O_3$ was continuously reused 5 times, decomposition of SMX was a little lowered, but the activity of catalyst was overall very stable.

• Nutrition Research and Practice
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• v.13 no.4
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• pp.352-357
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• 2019

BACKGROUND/OBJECTIVES: Youth is the crucial stage between childhood and adulthood during which an individual acquires new behavior and practices including dietary habits, that may be influenced by his peers, social circle, nutrition knowledge level and other factors. The increase in awareness of young adults is of special importance from the perspective of health and prevention of obesity related chronic diseases. To measure the nutrition literacy level of university students using the Turkish version of Adolescent Nutrition Literacy Scale (ANLS). We evaluated their food habits using the Adolescent Food Habit Checklist (AFHC) tool and analysed it, if the eating habits were affected by nutrition literacy level. SUBJECTS/METHODS: A cross-sectional descriptive study was conducted on randomly selected 276 students studying in the Faculty of Health Sciences of Istanbul Aydin University, Turkey. Data was collected by means of ANLS and AFHC tools by face to face interview method. SPSS statistical sofware (IBM SPSS Statistics 19) was used to analyse the obtained data. RESULTS: Participants comprised of 47.1% males and 52.9% females with mean age of $20.0{\pm}1.60years$. Mean body mass index (BMI) was determined as $22.4{\pm}3.76$ ($23.6{\pm}3.63$ males $21.3{\pm}3.57$ females). Functional, interactive and critical nutritional literacy scores for male participants were $22.49{\pm}5.71$, $17.45{\pm}4.84$, and $28.28{\pm}7.13$ respectively (total $64.98{\pm}10.15$). For females the values were $24.66{\pm}5.13$, $20.17{\pm}4.28$, and $32.20{\pm}5.65$ (total $69.72{\pm}8.59$) respectively. For all the three sub-categories of nutrition literacy, the scores acquired by females were significantly higher than males (P < 0.001). In the AFHC tool, the mean score acquired by males were $9.26{\pm}4.18$ whereas for females it was $10.37{\pm}3.40$ significantly higher as compared to males (P = 0.007). CONCLUSION: The food habits of female participants were better than males; in accordance with their nutrition literacy status. It may be concluded that food habits are influenced by nutrition literacy and therefore stress much be given to increase the nutrition awareness among children youth as well as adults.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.1-9
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• 2019

GGBFS(Ground Granulated Blast Furnace Slag), one of the representative concrete mineral admixtures, improves the long-term durability and engineering performance of concrete by latent hydraulic activity. In this study, considering 3 levels of W/B(0.37, 0.42, 0.47) and GGBFS replacement ratio(0 %, 30 %, 50 %), durability performances for chloride attack are evaluated, and equations which predict behavior of accelerated chloride diffusion are proposed. Also, the relationship between accelerated chloride diffusion coefficient and passed charge is evaluated. In target curing day, accelerated chloride diffusion tests(Tang's method, ASTM C 1202) and compressive strength(KS F 2405) are performed. In the 730 day's results of accelerated chloride diffusion coefficient, GGBFS concrete has up to 28 % of decreasing ratio compared to OPC concrete, and in those of passed charge, GGBFS concrete has up to 29 % of decreasing ratio compared to OPC concrete. Also, it is deemed that the impact of variation of W/B is less in GGBFS concrete than in OPC concrete. The equations which predict accelerated chloride diffusion coefficient and passed charge are drawn, based on the characteristics of mixture and test results. The equation which predicts passed charge shows slightly higher coefficient of determination than that which predicts accelerated chloride diffusion coefficient.

• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.85-93
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• 2019

The purpose of this study is to identify the influence of demographic characteristics such as inappropriate lifestyle, stress, and health status among health risk factors of early adolescents according to gender. There is a gender difference in the perception of mental and physical health of early adolescents, and the result can be different in behavior patterns between men and women. This study was conducted to identify the health risk factors as independent variables for early adolescents in Daegu and Gyeongbuk area, and to analyze the determinants of gender (male, female) differences by parents, family environment, friends, academic background, appearance, grade, location, school grades, family situation, and health status as demographic factors. And, the Odds Ratio of the early adolescents was analyzed through logit analysis and the differences according to the influence relationship of each of them were examined. As a result of the analysis, the more the sleep and physical activity, parents, home environment, friends, academic background, and appearance are increased, the more the influence is likely to become on the male students. On the contrary, the rest of the health risk factors can increase, and the threat to the health risk factors is likely to become severe to the female students.Among them, it is necessary to develop a pre-preventive program for early adolescents' health risk factors, provide basic data for practical application in the field, and seek a detailed program according to the gender of early adolescents.

• Management & Information Systems Review
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• v.38 no.1
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• pp.43-61
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• 2019

It is true that there are not enough empirical studies on the companionship to social welfare workers until now. Thus, this study has reduced the need to demonstrate the causal relationship between compassion experienced and outcome variables by social workers. The purpose of this study is to demonstrate the impact of the compassion experienced by social workers in social welfare facilities on positive psychological capital, and to the psychological effect formed by the psychosomatic concentration. Third, the purpose of this study is to verify the effect of positive psychological capital on the relationship between compassion and affective commitment, and fourth, the relationship between positive psychological capital and organizational identification. For empirical research, the hypothesis was verified after a survey of 369 social workers at social welfare facilities in Seoul and Gyeonggi Province. The study showed that the compassion experienced by social workers had a positive(+) effect on positive psychological capital, and that positive psychological capital had a positive(+) effect on affective commitment. In the relationship between compassion and affective commitment, the effect of the mediation of positive psychological capital has also been proven to be significant. In addition in the relationship between positive psychological capital and affective commitment, it has been noted that organizational identification has also been proven to be significant. Therefore, this study has theoretical implications for the mediating effect of the positive psychological capital and the moderating effect of organizational identification in relation to the compassion. This study will have practical implications for enhancing social workers' behavior to be more compassionate in their attitude to customers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.627-635
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• 2019

A programmable drone is a drone developed not only to experience the basic principles of flight but also to control drones through Arduino-based programming. Due to the nature of the training drones, the main users are students who are inexperienced in controlling the drones, which often cause frequent collisions with external objects, resulting in high damage to the drones' frame. In this study, the structural stability of the drone was evaluated by means of a structural dynamics based collision simulation for educational drone frame. Collision simulations were performed on three cases according to the impact angle of $0^{\circ}$, $+15^{\circ}$ and $-15^{\circ}$, using an analytical model with approximately 240,000 tetrahedron elements. Using ANSYS LS-DYNA, which provides excellent functions for the simulation of the dynamic behavior of three-dimensional structures, the stress distribution and strain generated on the drone upper, the drone lower, and the ring assembly were analyzed when the drones collided against the wall at a rate of 4 m/s. Safety factors resulting from the equivalent stress and the yield strain were calculated in the range of 0.72 to 2.64 and 1.72 to 26.67, respectively. To ensure structural stability for areas where stress exceeds yield strain and ultimate strain according to material properties, the design reinforcement is presented.