• Wind and Structures
• /
• v.28 no.2
• /
• pp.71-87
• /
• 2019

The yaw and interference effects of blades affect aerodynamic performance of large wind turbine system significantly, thus influencing wind-induced response and stability performance of the tower-blade system. In this study, the 5MW wind turbine which was developed by Nanjing University of Aeronautics and Astronautics (NUAA) was chosen as the research object. Large eddy simulation on flow field and aerodynamics of its wind turbine system with different yaw angles($0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ and $45^{\circ}$) under the most unfavorable blade position was carried out. Results were compared with codes and measurement results at home and abroad, which verified validity of large eddy simulation. On this basis, effects of yaw angle on average wind pressure, fluctuating wind pressure, lift coefficient, resistance coefficient,streaming and wake characteristics on different interference zone of tower of wind turbine were analyzed. Next, the blade-cabin-tower-foundation integrated coupling model of the large wind turbine was constructed based on finite element method. Dynamic characteristics, wind-induced response and stability performance of the wind turbine structural system under different yaw angle were analyzed systematically. Research results demonstrate that with the increase of yaw angle, the maximum negative pressure and extreme negative pressure of the significant interference zone of the tower present a V-shaped variation trend, whereas the layer resistance coefficient increases gradually. By contrast, the maximum negative pressure, extreme negative pressure and layer resistance coefficient of the non-interference zone remain basically same. Effects of streaming and wake weaken gradually. When the yaw angle increases to $45^{\circ}$, aerodynamic force of the tower is close with that when there's no blade yaw and interference. As the height of significant interference zone increases, layer resistance coefficient decreases firstly and then increases under different yaw angles. Maximum means and mean square error (MSE) of radial displacement under different yaw angles all occur at circumferential $0^{\circ}$ and $180^{\circ}$ of the tower. The maximum bending moment at tower bottom is at circumferential $20^{\circ}$. When the yaw angle is $0^{\circ}$, the maximum downwind displacement responses of different blades are higher than 2.7 m. With the increase of yaw angle, MSEs of radial displacement at tower top, downwind displacement of blades, internal force at blade roots all decrease gradually, while the critical wind speed decreases firstly and then increases and finally decreases. The comprehensive analysis shows that the worst aerodynamic performance and wind-induced response of the wind turbine system are achieved when the yaw angle is $0^{\circ}$, whereas the worst stability performance and ultimate bearing capacity are achieved when the yaw angle is $45^{\circ}$.

• Journal of Sensor Science and Technology
• /
• v.28 no.1
• /
• pp.41-46
• /
• 2019

In order to develop novel thermal imaging materials for microbolometer applications, $[(Ni_{0.3}Mn_{0.7})_{1-x}Cu_x]_3O_4$ ($0.18{\leq}x{\leq}0.26$) thin films were fabricated using metal-organic decomposition. Effects of Cu content on the electrical properties of the annealed films were investigated. Spinel thin films with a thickness of approximately 100 nm were obtained from the $[(Ni_{0.3}Mn_{0.7})_{1-x}Cu_x]_3O_4$ films annealed at $380^{\circ}C$ for five hours. The resistivity (${\rho}$) of the annealed films was analyzed with respect to the small polaron hopping model. Based on the $Mn^{3+}/Mn^{4+}$ ratio values obtained through x-ray photoelectron spectroscopy analysis, the hopping mechanism between $Mn^{3+}$ and $Mn^{4+}$ cations discussed in the proposed study. The effects of $Cu^+$ and $Cu^{2+}$ cations on the hopping mechanism is also discussed. Obtained results indicate that $[(Ni_{0.3}Mn_{0.7})_{1-x}Cu_x]_3O_4$ thin films with low temperature annealing and superior electrical properties (${\rho}{\leq}54.83{\Omega}{\cdot}cm$, temperature coefficient of resistance > -2.62%/K) can be effectively employed in applications involving complementary metal-oxide semiconductor (CMOS) integrated microbolometer devices.

• The Korean Journal of Archival Studies
• /
• no.58
• /
• pp.31-63
• /
• 2018

The foremost priority for establishing record management of public institutions is strengthening the function and role of the records centers in the institutions and creating the foundation of the organization and personnel for demonstrating professionalism of archivists. However, concept of current records center is not clear and there is no substance of the organization. It also says that once a records manager is deployed, a records center is founded since appointment criteria for archivists is prone to be interpreted subjectively by the institutions. Therefore, it's time for more concrete improvements to resolve these issues. This research analyses some problems found in the system of records centers in the main office and district offices of education focusing on the environment of them. The problems are centers without substance in district offices of education because of the organization structure that all authority has been assembled in the main office, and the reality of records managers who have fallen into records discarders, etc. To solve these problems, this paper proposes changing the appointment criteria for archivists, operating an integrated records center reflecting the intensive working system, and legislating special act on record management of educational institutions.

• Journal of Digital Convergence
• /
• v.17 no.9
• /
• pp.97-104
• /
• 2019

With the development and spread of smart devices, the proportion of mobile shopping is gradually increasing, and the market for mobile gift certificates is also increasing. This study examines the usage status and acceptance attitude of mobile gift certificates for university students who are major customers of mobile gift certificates. Also, based on the extended integrated technology acceptance model (UTAUT2), the results of the analysis of the mediating effect of the intention of the user on the relationship between acceptance of mobile vouchers and recommendation intention were presented. As a result of the analysis, it was shown that the effort expectation, hedonic motivation, price utility, and habit had significant influence on the intention to use the mobile gift certificates. Also, the intention to use mobile gift certificates has mediating effects between effort expectation, hedonic motivation, price utility and recommendation intention. The results of this study can be applied to strategic marketing such as recruitment of new customers through mobile gift certificates while explaining customers' acceptance of technology to mobile gift vouchers or future prospective customers.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.6
• /
• pp.350-361
• /
• 2019

The fourth industrial revolution based on the intelligent revolution has revolutionized the society as a whole, and it has also affected the defense sector. Various aspects of the war have been changing with the development of technology. In particular, various strategies such as research and development of core technology related to defense unmanned system field and infrastructure are being established based on the fourth industrial revolution technology. In this paper, we have conducted a study to select the technology required for maritime unmanned systems, which can be considered as a priority consideration for the future development of the core technology to be secured prior to the development of the weapon system. First, the core technology prioritization model for the marine unmanned system was established, and the technology fields of the unmanned robot were reclassified and integrated in the related literature such as the classification of the defense technology standard. For the empirical analysis, a questionnaire survey was conducted for 12 specialists who are engaged in the planning of weapons systems, and the importance of technical fields that require development in the development of marine unmanned systems was analyzed. As a result, it was possible to identify the key technology areas that should be considered in selecting the key technologies proposed by the military groups, research institutes, and companies. This could contribute to the establishment of the technology roadmap to develop the marine unmanned system from the future point of view.

• Journal of Digital Convergence
• /
• v.17 no.11
• /
• pp.61-70
• /
• 2019

The The government has recently announced its mid- to long-term plans for promoting art. With the advent of the 4th industrial revolution, contemporary art contents that are integrated with Intelligent Information Technologies such as Artificial Intelligence (AI), Virtual Reality (VR), and Big Data are being introduced, and social interest in humanities and creative convergence is rising. In addition, the industrialization of the art market is expanding amid the rising popularity of art among the general public and the growing interest of art as an investment replacement system, along with the strengthening of the creative personality education of our Education Ministry. Therefore, it is necessary to establish a strategy for transparency and revitalization of the art market by providing comprehensive information such as search functions, analysis data, and criticism by writer and price. This paper has established an information system plan for the establishment of an online supply system for art transaction information, providing auction transaction information for art market, providing report and news for art market, providing public relations platform, and providing art market analysis service and membership relationship management service. To this end, the future model was established through environmental analysis and focus analysis of the art market, and strategic tasks and implementation plans were established accordingly.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.20 no.1
• /
• pp.10-21
• /
• 2021

This study analyzed how external variables, such as the supply policy of shared bicycles and the spread of infectious diseases, affect the demand for shared bicycle use in the COVID-19 era. In addition, this paper presents a methodology for more accurate predictions. The Seasonal Auto-Regulatory Integrated Moving Average with Exogenous stressors methodology was applied to capture the effects of exogenous variables on existing time series models. The exogenous variables that affected the future demand for shared bicycles, such as COVID-19 and the supply of public bicycles, were statistically significant. As a result, from the supply volume and COVID-19 outbreak according to the scenario, it was estimated that approximately 46,000 shared bicycles would be supplied by 2022, and the COVID-19 cases would continue to be at the current level. In addition, approximately 32 million and 45 million units per year will be needed in 2021 and 2024, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.3
• /
• pp.362-373
• /
• 2021

This is an action research study of mixed methodology design to confirm the implementation process and effects of applying visual thinking and window paning on improving nursing ethics and professional courses. Based on the conceptual model for action research, a quantitative and qualitative approach was taken. The data was collected and analyzed in an integrated manner. The survey analysis was done using the SPSS WIN 23.0 program. The participants were interviewed after experiencing the techniques in class and content analysis was used on the answers. As a result of applying visual thinking and window paning, ethical decision-making confidence (t=6.748, p<.001) and nursing professional intuition (t=-3.52, p<.001) showed statistically significant changes. There was, however, no significant change in biomedical ethics consciousness (t=1.291, p=.199). Qualitative analysis found that they had fresh experience, an unfamiliar but comfortable feeling, feeling of being mine, insufficient time, systematic case study approach based on theory, were able to cultivate cooperation and coordination ability through discussion and experience in various professional fields, pride, ethical responsibility consciousness and were able to apply learning content in the field. Visual thinking and window paning foster diverse competencies in nursing education and help integrative learning. Therefore, based on the results it is proposed that visual thinking and window paning are applied to the improvement of instruction in other courses to develop core nursing competency.

• The Journal of the Korea Contents Association
• /
• v.21 no.6
• /
• pp.248-260
• /
• 2021

This study assumes that the smooth school life of adolescents from multicultural families is recognized as an important part of multicultural support policies and practices as a basis for realizing an integrated society, and system elements that are meaningful for their flexibility to adapt to school (individuals, families, schools) By empirically analyzing the effect of, we tried to bring out highly effective implications for the composition of a multidimensional practice system. Therefore, this study is a causal model in which self-identity (individual factor) and parental parenting attitude (family factor), which are important variables for each system level, are set as independent variables, and school support (school factor) consisting of teacher support and companion support is set as control variables. After collecting data through a questionnaire survey by interviews with 162 middle and high school students in Gyeonggi and Gangwon regions, the effect was analyzed through multiple regression analysis. As a result of the analysis, it was confirmed that school support has a very important static moderating effect in the positive (+) effect of adolescents' self-identity and parenting attitude on school adaptability. It was confirmed that the modulating effect is relatively more important.

• Korean Journal of Ecology and Environment
• /
• v.53 no.4
• /
• pp.311-323
• /
• 2020

We analyzed food sources of 45 fish species in 28 genera of 12 families based on literature data in freshwater ecosystems of South Korea. The food sources of 45 fish species included in a total of 26 phyla, 42 classes, 94 orders, 189 families and 294 genera. Among them, animal food sources were 16 phyla, 24 classes, 54 orders, 126 families and 212 genera, whereas plant food sources were relatively small with 10 phyla, 18 classes, 42 orders, 63 families and 82 genera. The animal food sources were classified into Arthropod, Insecta, Diptera and Chironomidae according to taxa. Meanwhile, Bacillariophyta, Bacillariophyceae, Cymbellales and Cymbellaceae were the most abundant among the plant sources. Self-Organized Map (SOM) and network analysis were conducted the food sources were classified into taxonomic groups and the feeding types of fish : 45 fish species were divided into five groups, characterizing 1) fishvores, 2) invertebratevores, planktivores including 3) zooplankton and 4) phytoplankton, and 5) omnivores. The network analysis presented link association between fishes and food sources. Macroinvertebrate including diptera and ephemeroptera were revealed as hub food sources based on network analysis. This literature study would expect that the application model with the food source of fish could be utilized for the evaluation of the food network or chain in freshwater ecosystems.