• 한국항공운항학회지
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• 제26권4호
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• pp.122-128
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• 2018

A compound drone that combines a fixed wing and a rotary wing is an aircraft that can take off and landing vertically, and can increase flight time and fly faster with fixed wings. The compound drones are divided into many types depending on the method of adding the thrust vectoring or the lift fan and the position of the rotor. In this study, we designed and fabricated a composite drone with four V-TOL motors in a fixed-wing, and assigned missions to the aviation body, hence judged mission accuracy using the actual flight test. The design process and the mission evaluation process employed in this study can be utilized on the development of various unmanned aerial vehicle.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1008-1016
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• 2019

In the SG (steam generator) of PWR (pressurized water reactor) for a nuclear plant, hundreds of U-shaped tubes are used for the heat exchanger system. They interact with primary pressurized cooling water flow, generating flow-induced vibration in the secondary flow region. A simplified U-tube model is proposed in this study to apply for experiment and its counterpart computation. Using the commercial code, ANSYS-CFX, we first verified the Moody chart, comparing the straight pipe theory with the results derived from CFD (computational fluid dynamics) analysis. Considering the virtual mass of fluid, we computed the major modes with the low natural frequencies through the comparison with impact hammer test, and then investigated the effect of pump flow in the frequency domain using FFT (fast Fourier transform) analysis of the experimental data. Using two-way fluid-structure interaction module in the CFD code, we studied the influence on mean flow rate to generate the displacement data. A feasible CFD method has been setup in this research that could be applied potentially in the field of nuclear thermal-hydraulics.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.622-625
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• 2016

우리나라는 삼면이 바다로 구성되어 있고 산악지형이 65% 이상이며 강수량이 높은 편이다. 따라서 차량 전복 및 추락 사고가 빈번히 일어나고 있어 이에 대비한 인명구조시스템 개발이 시급히 요구되고 있다. 본 논문에서는 차량 전복 및 추락사고 대처용 인명구조 시스템을 설계 및 구현하고 시험을 통해 기능을 검증하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.670-671
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• 2016

자동화 수동변속기는 수동변속기에 액츄에이터를 설치하여 자동으로 수동변속기를 변속할 수 있게 한 변속기로써, 자동화 수동변속기의 조작 편의성과 수동변속기 수준의 높은 연비로 인해 대형 상용차에 많이 적용되고 있다. 대형 상용차에 적용되는 12단 자동화 수동변속기는 다른 자동 변속기와 마찬가지로 자동변속로직과 변속맵에 의해 변속시점을 결정하지만 기존의 방식으로는 변속충격, 클러치 마모, 연비저하 등의 문제점이 발생할 수 있다. 본 논문은 12단 자동화 수동변속기에 알맞은 변속로직 및 변속맵의 설계와 성능확인시험에 대한 내용을 다루고 있다.

• Steel and Composite Structures
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• 제31권5호
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• pp.437-452
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• 2019

In this study, in-situ static and dynamic tests of four pre-stressed concrete (PC) track beams with different span lengths and curvatures in a straddle monorail transit system were reported. In the static load tests, the strain and deflection at critical sections of the PC track beams were measured to determine the load bearing capacity and stiffness. The dynamic responses of strain, deflection, acceleration, and displacement at key positions of the PC track beams were measured under different train speeds and train loads to systematically study the dynamic behaviors of the PC track beams. A three-dimensional finite element model of the track beam-vehicle coupled vibration system was established to help understand the dynamic behavior of the system, and the model was verified using the test results. The research results show that the curvature, span length, train speed, and train loads have significant influence on the dynamic responses of the PC track beams. The dynamic performance of the PC track beams in the curve section is susceptible to dynamic loads. Appropriate train loads can effectively reduce the impact of the train on the PC track beam. The PC track beams allow good riding comfort.

• 한국수소및신에너지학회논문집
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• 제30권3호
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• pp.237-242
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• 2019

In the hydrogen refueling station (HRS), it is need the pre-cooling system (PCS) to limit the inside temperature ($85^{\circ}C$) of the onboard thank (700 bar) and to charge the hydrogen at short time (within 3 minutes) to fuel cell electric vehicle (FCEV). From those safety reasons, the temperature of hydrogen gas must be controled $-33^{\circ}C$ to $-40^{\circ}C$ in PCS. The cooling test of the gaseous ($N_2$, He, $H_2$) was carried out using heat exchanger (pre-cooler) by indirect cooling and direct cooling method. It was confirmed that the temperature of hydrogen gas had below $-40^{\circ}C$ at below $-75^{\circ}C$ of chiller temperature in direct cooling.

• Design & Manufacturing
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• 제15권1호
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• pp.66-71
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• 2021

In this study, die turning injection(DTI) mold design for manufacturing reservoir fluid tanks used for cooling in-vehicle batteries, inverters, and motors was conducted based on multi-field CAE. Part design, performance evaluation, and mold design of the reservoir fluid tank was performed. The frequency response characteristics through modal and harmonic response analysis to satisfy the automotive performance test items for the designed part were examined. Analysis of re-melting characteristics and structural analysis of the driving part for designing the rotating die of the DTI mold were performed. Part design was possible when the natural frequency performance value of 32Hz or higher was satisfied through finite element analysis, and the temperature distribution and deformation characteristics of the part after injection molding were found through the first injection molding analysis. In addition, it can be seen that the temperature change of the primary part greatly influences the re-melting characteristics during the secondary injection. The minimum force for driving the turning die of the designed mold was calculated through structural analysis. Hydraulic system design was possible. Finally, a precise and efficient DTI mold design for the reservoir fluid tank was possible through presented multi-field CAE process.

• 국제초고층학회논문집
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• 제9권4호
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• pp.351-360
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• 2020

Monitoring civil structures periodically is necessary for ensuring the fitness of the structures. Cracks on inner and outer surfaces of the building plays a vital role in indicating the health of the building. Conventionally, human visual inspection techniques were carried up to human reachable altitudes. Monitoring of high rise infrastructures cannot be done using this primitive method. Also, there is a necessity for more accurate prediction of cracks on building surfaces for ensuring the health and safety of the building. The proposed research focused on developing an efficient crack classification model using Transfer Learning enabled EfficientNet (TL-EN) architecture. Though many other pre-trained models were available for crack classification, they rely on more number of training parameters for better accuracy. The TL-EN model attained an accuracy of 0.99 with less number of parameters on large dataset. A bench marked METU dataset with 40000 images were used to test and validate the proposed model. The surfaces of high rise buildings were investigated using vision enabled Unmanned Arial Vehicles (UAV). These UAV is fabricated with TL-EN model schema for capturing and analyzing the real time streaming video of building surfaces.

• 한국정보시스템학회지:정보시스템연구
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• 제30권4호
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• pp.95-118
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• 2021

Purpose This study verified the moderating effect of consumer knowledge in relation to the factors affecting the acceptance intention of autonomous vehicles by adding trust to the United Theory of Acceptance and Use of Technology model for the commercialization of autonomous vehicles. Design/methodology/approach For this purpose, this study conducted a survey on general consumers who are interested in automobiles. A total of 250 questionnaires were distributed and collected, and 242 questionnaires were used for analysis. To test the hypotheses, multiple regression analysis and multiple group analysis were performed. Findings Performance expectations, effort expectations, social influence, and trust were found to have a positive effect on the acceptance intention of autonomous vehicles. In addition, consumer knowledge between performance expectation and acceptance intention and between effort expectation and acceptance intention was confirmed as a variable that can moderate the relationship.

• International Journal of Internet, Broadcasting and Communication
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• 제14권2호
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• pp.47-54
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• 2022

For safe driving of autonomous vehicles, road damage detection is very important to lower the potential risk. In order to ensure safety while an autonomous vehicle is driving on the road, technology that can cope with various obstacles is required. Among them, technology that recognizes static obstacles such as poor road conditions as well as dynamic obstacles that may be encountered while driving, such as crosswalks, manholes, hollows, and speed bumps, is a priority. In this paper, we propose a method to extract similarity of images and find damaged road images using OpenCV image processing and CNN algorithm. To implement this, we trained a CNN model using 280 training datasheets and 70 test datasheets out of 350 image data. As a result of training, the object recognition processing speed and recognition speed of 100 images were tested, and the average processing speed was 45.9 ms, the average recognition speed was 66.78 ms, and the average object accuracy was 92%. In the future, it is expected that the driving safety of autonomous vehicles will be improved by using technology that detects road obstacles encountered while driving.