• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1674-1685
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• 2022

The ball valve is an important device in the pipeline transportation system of nuclear power plants. Its operational stability and safety directly affect the normal working of nuclear power plants. In this study, the transient numerical simulation of the opening and closing process of a ball valve was conducted on the basis of the flow interruption capability experiment of the ball valve by using the moving mesh method and inlet and outlet variable boundary conditions. The flow rate and pressure difference with time of the opening and closing process of the ball valve were studied. The internal flow characteristics of the ball valve under different relative openings were analyzed in conjunction with the typical back-step flow structure. Results show that the transient numerical results agree well with the experimental results. The internal flow characteristics of the ball valve are similar at the same opening during opening and closing process. At small opening, the spool and outlet channels easily form a back-step flow structure. The disappearance and generation of backflow vortices during opening and closing occur at 85% opening and 75% opening, respectively. With the decrease in opening degree, the difference in vortex core area in the flow channel of the ball valve spool in the opening and closing process gradually appears. The research results provide some reference value for the design and optimization of ball valves.

• 한국정보통신학회논문지
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• 제26권10호
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• pp.1447-1452
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• 2022

세계 10대 도시이며 Metro City인 서울특별시는 인쇄, 봉제, 기계금속 등 전통적인 도심제조업이 분포되어있다. 이들 제조업 집적지 내 소상공인은 서로 상부상조 하는 형태로 발전해왔다. 집적지의 특성상 각 공정은 개별 업체가 담당한다. 상대적으로 영세한 소상공인이 공정 간 실시간 물류 이동 정보를 제공하는 주문처리 서비스를 준비하기에 어려운 현실이다. 본 논문에서는 패키지(Package) 제조 및 특수인쇄 분야 소상공인의 원활한 수주, 배송 처리를 위해 기존 물류 Data를 수집, 분석하고 CRNN, k-NN, ID3 Decision Tree algorithm을 적용한 인공지능 Fulfillment Service Platform 시스템을 설계한다. 본 연구를 통하여 집적지 소상공인 누구나 Cloud 네트워크를 통하여, 개별 수주, 배송 맞춤서비스를 사용할 수 있게 함으로써 매출 증대 및 역량 향상에 크게 기여할 것으로 기대한다.

• Advances in nano research
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• 제11권6호
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• pp.581-593
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• 2021

This model is proposed to describe the buckling behavior of Carbon Nanotubes (CNTs) embedded in an elastic medium taking into account the combined effects of the magnetic field, the temperature, the nonlocal parameter, the number of walls. Using Eringen's nonlocal elasticity theory, thin cylindrical shell theory and Van der Waal force (VdW) interactions, we develop a system of partial differential equations governing the buckling response of CNTs embedded on Winkler, Pasternak, and Kerr foundations in a thermal-magnetic environment. The pre-buckling stresses are obtained by applying airy's stress function and an adjacent equilibrium criterion. To estimate the nonlocal critical buckling load of CNTs under the simultaneous effects of the magnetic field, the temperature change, and the number of walls, an optimization technique is proposed. Furthermore, analytical formulas are developed to obtain the buckling behavior of SWCNTs embedded in an elastic medium without taking into account the effects of the nonlocal parameter. These formulas take into account VdW interactions between adjacent tubes and the effect of terms involving differences in tube radii generally neglected in the derived expressions of the critical buckling load published in the literature. Most scientific research on modeling the effects of magnetic fields is based on beam theories, this motivation pushes me to develop a cylindrical shell model for studying the effect of the magnetic field on the static behavior of CNTs. The results show that the magnetic field has significant effects on the static behavior of CNTs and can lead to slow buckling. On the other hand, thermal effects reduce the critical buckling load. The findings in this work can help us design of CNTs for various applications (e.g. structural, electrical, mechanical and biological applications) in a thermal and magnetic environment.

• 로봇학회논문지
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• 제17권2호
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• pp.142-151
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• 2022

With the advent of the 4th industrial revolution, autonomous driving technology is being commercialized in various industries. However, research on autonomous driving so far has focused on platforms with wheel-type platform. Research on a tracked platform is at a relatively inadequate step. Since the tracked platform has a different driving and steering method from the wheel-type platform, the existing research cannot be applied as it is. Therefore, a path-tracking algorithm suitable for a tracked platform is required. In this paper, we studied a path-tracking algorithm for a tracked platform based on a GPS sensor. The existing Pure Pursuit algorithm was applied in consideration of the characteristics of the tracked platform. And to compensate for "Cutting Corner", which is a disadvantage of the existing Pure Pursuit algorithm, an algorithm that changes the LAD according to the curvature of the path was developed. In the existing pure pursuit algorithm that used a tracked platform to drive a path including a right-angle turn, the RMS path error in the straight section was 0.1034 m and the RMS error in the turning section was measured to be 0.2787 m. On the other hand, in the variable LAD algorithm, the RMS path error in the straight section was 0.0987 m, and the RMS path error in the turning section was measured to be 0.1396 m. In the turning section, the RMS path error was reduced by 48.8971%. The validity of the algorithm was verified by measuring the path error by tracking the path using a tracked robot platform.

• 문화기술의 융합
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• 제8권5호
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• pp.591-596
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• 2022

다양한 산업분야에서 사용되는 4절 링크기구는 링크 길이가 고정되어 있으므로 기구의 움직임을 변경하기 위해서는 독립적인 링크기구나 제어장치를 추가해야 하는 불편함이 있다. 따라서 본 논문에서는 상황에 따라 링크기구의 운동을 선택적으로 제어할 수 있도록 링크 길이가 조절되는 가변형 4절 링크기구를 설계하였으며 링크기구에 의해 구동되는 제품인 선풍기에 적용하여 그 타당성을 검증하였다. 바람 범위의 효율성을 고려하여 선풍기 회전각도를3단계로 분할하였으며 각 구간에 필요한 링크 길이를 계산하였다. 또한, 원통캠을 이용하여 링크 길이를 조절하였으며 선풍기의 회전각도 조절 작동 여부를 실제 제작 및 측정을 통해 확인하였다. 본 논문에서 제시한 가변형 링크기구는 산업용 로봇이나 연료 밸브 시스템 등과 같은 4절링크 적용 제품의 효율성을 향상시킬 수 있을 것으로 기대된다.

• Tribology and Lubricants
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• 제38권5호
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• pp.179-184
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• 2022

The power train of transmission for 21-ton grade wheel excavator makes use of a complex gear train composed of a planetary and helical gear system to drive the wheel excavator by transmitting power to the axle. The complex gear train with a shift mode is an important part of the transmission because of strength problems in an extreme environment. To calculate the specifications of the complex gear train and analyze the gear bending and compressive stresses of the complex gear train, this study analyzes gear bending and compressive stresses accurately for the optimal design of the complex gear train with respect to cost and reliability. In this article, the gear bending and compressive stresses of the complex gear train are calculated using the Lewes and Hertz equation. Evaluating the results with the data of the allowable bending and compressive stress from the stress and number of cycles curves of the gears verified the calculated specifications of the complex gear train. A computer structure analysis is performed with the 3D model of the planetary and helical gears to analyze the structure strength of the complex gear train. The results demonstrate that the durability and strength of the complex gear train are safe, because the safety factors of the bending and compressive stresses are more than 1.0.

• 로봇학회논문지
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• 제18권3호
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• pp.251-259
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• 2023

In the path traveling of differential-drive robots, the steering controller plays an important role in determining the path-following performance. When a robot with a pure-pursuit algorithm is used to continuously drive a right-angled driving path in an unstructured environment without turning in place, the robot cannot accurately follow the right-angled path and stops driving due to the ground and motor load caused by turning. In the case of pure-pursuit, only the current robot position and the steering angle to the current target path point are generated, and the steering component does not reflect the speed plan, which requires improvement for precise path following. In this study, we propose a driving algorithm for differentially driven robots that enables precise path following by planning the driving speed using the radius of curvature and fusing the planned speed with the steering angle of the existing pure-pursuit controller, similar to the Model Predict Control control that reflects speed planning. When speed planning is applied, the robot slows down before entering a right-angle path and returns to the input speed when leaving the right-angle path. The pure-pursuit controller then fuses the steering angle calculated at each path point with the accelerated and decelerated velocity to achieve more precise following of the orthogonal path.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.219-221
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• 2022

세계 10대 도시이며 Metro City인 서울특별시는 인쇄, 봉제, 기계금속 등 전통적인 도심제조업이 분포되어있다. 이들 제조업은 세부 업종 및 공정에 따라 소상공인 집적지를 형성해 서로 상부상조 하는 형태로 발전해왔다. 집적지의 특성상 집적지 내 각 공정별 업체 간 물류는 신속히 이루어지고 있으나 상대적으로 영세한 소상공인이 최종 단계의 완제품 수요자에 대한 주문처리 서비스를 준비하기에는 어려운 현실이다. 따라서 원활한 수주, 배송처리를 위해 집적지 상공인을 위한 통합수주 Fulfillment Service Platform 도입이 시급하다. 본 논문에서는 전통 도심산업 중 인쇄업 소상공인의 기존 Fulfillment Service data를 수집, 분석하고 CRNN, k-NN, ID3 Decision Tree algorithm을 적용한 인공지능 Fulfillment Service Platform 시스템을 설계한다. 본 연구를 통하여 집적지 소상공인 누구나 활용할 수 있는 개별 수주, 배송 맞춤서비스 사용이 가능하게 함으로써 소상공인 매출 증대 및 역량 향상에 크게 기여할 것으로 기대한다.

• Earthquakes and Structures
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• 제23권2호
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• pp.151-168
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• 2022

Torsion is one of the most important causes of building collapse during earthquakes. Sometimes, despite the symmetric form of the building, infill walls disturb the symmetry of the lateral resisting system. The purpose of this research is to investigate the effect of urban layout on developing torsion caused by infill walls. For this purpose, a typological study was conducted based on the conditions of perimeter walls on 364 buildings and then 9 cases were selected. The dimensions of the selected buildings are constant and the conditions of the perimeter walls including facades with openings and cantilevered facades are variable. The selected buildings with 60 different layouts of infill walls were analyzed and the behavior of each one was evaluated based on the torsional irregularity criteria of seismic codes. The results of the analyses showed that if the perimeter walls of a building are symmetric, asymmetric interior walls will not be important in developing torsion and effective parameters in symmetry of the perimeter infill walls are the number of walls, area of openings, aspect ratio, and construction details. Finally, architectural solutions to mitigate the torsional effects of infill walls were proposed for buildings with solid infill walls on some sides, for buildings where the perimeter walls of one side are on the cantilevered part, and for buildings where the perimeter walls of two adjacent sides are on the cantilevered part. In three-sided buildings, where two adjacent façades are cantilevered, it is often impossible to use the potential of the infill walls.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2021년도 추계학술발표대회
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• pp.371-374
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• 2021

자율주행 기술이 급속도로 발전하고 있지만, 자율주행 레이싱 기술과 관련 산업은 전세계적으로 아직 걸음마 수준이다. 본 연구팀은 국내 자율주행차 대표기업인 (주)언맨드솔루션에서 지원하는 플랫폼을 사용하여 자율주행 레이싱 제어 모델 프레임워크를 설계하고 기초 실험을 진행하였다. 제안된 자율주행 레이싱 제어 모델은 GPS 신호처리부, LiDAR 신호처리부, 영상처리부, 차량제어부, 추월/회피 제어부, 컨트롤러 통신부 등으로 구성된다. 실험을 통해 각 구성요소에 대한 기본 성능을 검증하였고, 레이싱에 최적화된 인공지능(AI) 기반 추월/회피 제어 알고리즘 개발을 위한 중요한 토대를 마련하였다. 본 연구를 바탕으로 2021년 11월에 국내 최초로 개최되는 세계 AI 로보카레이스 대회에 출전하여 제안된 자율주행 레이싱 제어 모델 프레임워크의 성능을 검증할 계획이다.