• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.187-192
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• 2018

This thesis is about the study of inverter terminal boxes in a explosion proof type exhaust fan that can control wind volume and operating time. In Korea, there is no ventilator to adjust the amount of wind and operating time when working in poor conditions. The purpose of the project is to create a explosion terminal box that can control the operating time and wind speed of a suitable explosion ventilator in hazardous environments. The two explosion-proof switches allow the operation time to be driven 1 hour, 3 hours and continuous time, and the speed of the induction motor rotation was set in 3 stages at 2000 rpm, 2600 rpm and 3000 rpm to control the volume. The tested motor used a half-horsepower barrier three-phase induction motor and a full-bridge inverter to set the desired flow rate and operating time.

• Journal of IKEEE
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• v.23 no.3
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• pp.1108-1111
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• 2019

This paper presents the comprehensive transformer design methodology with the winding method of automatic type suitable for LLC resonant converter. The problem with conventional LLC resonant transformer is that it is difficult to implement the winding method of automatic type because all windings are wound in one bobbin. Therefore, the LLC resonant transformer, which is capable of the winding method of automatic type to multiple section bobbin without insulation tape and barrier tape, is proposed in this paper and the design procedure of the proposed LLC resonant transformer is also shown. Modeling and analysis of the proposed LLC resonant transformer using Maxwell 3D simulation tool are described in detail and a protype 150W LLC resonant converter using the proposed LLC resonant transformer manufactured by 3D modelling is also verified through the experimental test.

• Tunnel and Underground Space
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• v.29 no.1
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• pp.38-51
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• 2019

Barcelona Basic Model (BBM) can describe not only swelling owing to decrease in effective stress, but also wetting-induced swelling due to decrease in suction. And the BBM can also consider increase in cohesion and apparent preconsolidation stress with suction, and decrease in the apparent preconsolidation stress with temperature. Therefore, the BBM is widely used all over the world to predict and to analyze coupled thermo-hydro-mechanical behavior of bentonite which is considered as buffer materials at the engineered barrier system in the high-level radioactive waste disposal system. However, the BBM is not well known in Korea, so this paper introduce the BBM to Korean rock engineers and geotechnical engineers. In this study, Modified Cam Clay (MCC) model is introduced before all, because the BBM was first developed as an extension of the MCC model to unsaturated soil conditions. Then, the thermo-elasto-plastic version of the BBM is described in detail.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.539-545
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• 2021

The effect of Sm₂O₃ doping on the microstructure and electrical properties of the ZPCCA-based varistors is comprehensively investigated. The increase of doping content of Sm₂O₃ results in better densification (from 5.70 to 5.82 g/cm³) and smaller mean grain size (from 7.8 to 4.1 ㎛). The breakdown electric field increases significantly from 2568 to 6800 V/cm as the doping content of Sm₂O₃ increases. The doping of Sm₂O₃ remarkably improves the nonlinear properties (increasing from 23.9 to 91 in the nonlinear coefficient and decreasing from 35.2 to 0.2 µA/cm² in the leakage current density). Meanwhile, the doping of Sm₂O₃ reduces the donor concentration (the range of 2.73 × 10¹⁸ to 1.18 × 10¹⁸ cm^-3) of bulk grain and increases the barrier height (the range of 1.10 to 1.49 eV) at the grain boundary. The density of the interface states decreases in the range of of 5.31 × 10¹² to 4.08 × 10¹² cm^-2 with the increase of doping content of Sm₂O₃. The dielectric constant decreases from 1594.8 to 507.5 with the increase of doping content of Sm₂O₃.

• Composites Research
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• v.34 no.1
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• pp.63-69
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• 2021

In order to develop an integrated heat dissipating material and gas barrier film for electronics, new polymer was designed and synthesized for preparing composites containing hexagonal boron nitride (hBN) filler. Depending on the size and content of the hBN filler, both thermal conductivity and oxygen transmission rate can be adjusted. The composite achieved a high thermal conductivity of 28.0 W·m-1·K-1 at most and the oxygen transmission rate was decreased by 62% compared to that of the filler free matrix. Effective filler aspect ratios could be estimated by comparing thermal conductivity and oxygen transmission rate with values predicted by theoretical models. Discrepancy on the aspect ratios extracted from thermal conductivity and oxygen transmission rate comparisons was also discussed.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.5
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• pp.61-72
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• 2019

The purpose of this study is to propose the clue of planning guideline for the elderly welfare center supporting the healthy life of the elderly through deriving the planning element of the elderly welfare center based on the Salutogenic Model(SM). The research method was proceeded with literature review. The meaning of Sense of Coherence(SOC) and Generalised Resistance Resources(GRR) which constitute Salutogenic Model is established. The correlation between SOC and GRR is analyzed. The conclusions of this study are as follows. First, EBD, BD, HD, UD, and BFD were studied as planning theories that could enhance the SOC of space. Second, based on the five planning theories, 43 planning elements needed for the elderly welfare center plan were derived. Third, as a result of classifying the plan elements based on the SOC, 'Manageability' is divided into 22 elements, 'Meaningfulness' is 11 and 'Comprehensibility' is 10 elements. Fourth, the details of the SOC items for each theory are as follows: BFD focuses on 'Manageability' with 'Manageability'(74%) and 'Comprehensibility'(26%), but 'Meaningfulness' does not exist. And UD regards 'Comprehensibility'(66%) as important, and 'Manageability' and 'Meaningfulness' as 17%. BD, on the other hand, has a high percentage of 'Meaningfulness'(70%), 'Comprehensibility'(21%) and 'Manageability'(9%). Next, the 'Manageability' of HD and EBD is 46%. And HD was 'Meaningfulness'(34%), 'Comprehensibility'(20%), and EBD was 'Meaningfulness'(30%) and 'Comprehensibility'(24%). The three items of SOC showed different distribution according to the spatial planning theory. As a result of the analysis, the spatial planning theory with the 'Comprehensibility' was related to Universal Design(UD), and the spatial planning theory with the 'Manageability' was related to Barrier-Free Design(BFD). In addition, the spatial planning theory of 'Meaningfulness' was related to Bio-philic Design(BD). Therefore, the plan of the elderly welfare center needs to approach the multidimensional design methodology to enhance the SOC(Sense of Coherence).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.43-50
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• 2021

Recently, researches and projects of companies based on artificial intelligence have been actively carried out. Various services and systems are being grafted with artificial intelligence technology. They become more intelligent. Accordingly, interest in deep learning, one of the techniques of artificial intelligence, and people who want to learn it have increased. In order to learn deep learning, deep learning theory with a lot of knowledge such as computer programming and mathematics is required. That is a high barrier to entry to beginners. Therefore, in this study, we designed and implemented a web-based deep learning platform called DeepBlock, which enables beginners to implement basic models of deep learning such as DNN and CNN without considering programming and mathematics. The proposed DeepBlock can be used for the education of students or beginners interested in deep learning.

• Journal of Appropriate Technology
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• v.6 no.2
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• pp.146-150
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• 2020

Assistive technologies for people with disabilities are often marginalized in the Fourth Industrial Revolution. In this paper, we intend to present the possibility of acquiring tactile information through the tactile display adapting an electromagnetic actuator. The multi-layered display designed for tactile communication has innovatively narrowed the size and spacing of cells in order to express pictures, maps, and graphics. This display has enabled the visually impaired to touch two-dimensional information combining with other assistive technologies so that. It would also provide a technical source of access to STEM education (Science, Technology, Engineering, and Mathematics) so that students will perform better and be better prepared for advanced education. Moreover, it can be applied to public infrastructure and transportation in smart-city projects on the globe. Hence, this paper introduces the principle of Electromagnetic-actuator and how it can be utilized in many diverse areas.

• Journal of the Korean Society of Safety
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• v.37 no.1
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• pp.70-77
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• 2022

The total number of Korean restaurants using delivery applications has substantially increased from 7.6% in 2018 to 11.2% in 2019. In 2020, the gross sales in the food delivery service market reached approximately 17 trillion won; this amount is virtually six times that in 2017 (i.e., 2 trillion won). Meanwhile, the annual average death toll of motorcycle riders increased by 3.5%, whereas the number of deaths due to other traffic accidents decreased by 8.2%. Consequently, the foregoing has become a critical social problem. Despite the continuing increase in the number of delivery riders due to the rapid expansion of the delivery industry, no appropriate safety management system has been established. Moreover, the government is experiencing difficulties in assessing the exact situation because of the absence of competent authority. In this study, fundamental data on the characteristics of delivery work and motorcycle accidents were collected through surveys and interviews; then, the influencing factors of traffic accidents were analyzed. Different influencing factors were identified: work experience as a rider; number of deliveries; whether to accept delivery requests in transit; manner of accepting delivery requests; and traffic law violations, such as speeding (for faster delivery) and running a red light. Because the motorcycle delivery industry has a relatively low job-entry barrier (i.e., special qualifications are not required), the riding skills of riders must be improved, and delivery companies must be technically developed to achieve a safe working environment. The results of this study can be utilized as fundamental data for system development or structural improvement of the delivery industry.

• Journal of Convergence for Information Technology
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• v.12 no.3
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• pp.151-157
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• 2022

The purpose of this study was to investigate the frequency characteristics of forced vibration considering the vehicle progress. And the vibration characteristics in frequency domain that occur, when vehicle passes the bump, were analyzed. The responses such as displacement, velocity and acceleration were obtained through numerical analysis, and FFT processing was performed to analyze the frequency response function(FRF) characteristics. In particular, the location of vehicle eigenmodes and external excitation modes was clearly shown and analyzed. In the forced vibration model by external force, the behavior of the eigenmode in power spectrum and real and imaginary parts were also analyzed. The mode characteristics were also analyzed in each FRF. It was approximated by assuming total excitation force by considering the exciting frequency using impulse and sine wave forces, which can give the amplitude and frequencies. The response characteristics of forced oscillations having different mass, damping and stiffness have been systematically discussed.