• International Journal of Railway
• /
• 제4권2호
• /
• pp.50-55
• /
• 2011

The dynamic stability of railway vehicle has long been one of the important issues in railway safety. The dynamic simulator has been used as a tool for investigating the dynamic stability of railway vehicles and wheel/rail interfaces. In particular, small scale simulators have been widely used in laboratory studies instead of full scale roller rigs which can be quite costly and rather inconvenient for testing out the effect of diverse design parameters. But techniques for design of a small scale simulator for the fundamental study about the dynamic characteristics of the wheel-rail systems and the bogie systems have not been well developed in Korea. Therefore, a research on the development of a small scale simulator for investigating bogie dynamics needs to be undertaken. The present paper investigates design of a small-scaled derailment simulator and the design of a small scale bogie. The simulator developed can be used to investigate the effect of diverse parameters such as attack angle, wheelbase and cant on dynamic behavior of the bogie and key dynamic performance parameters such as derailment coefficient and critical speed.

• 로봇학회논문지
• /
• 제18권3호
• /
• pp.285-292
• /
• 2023

Small-scale ground mobile robots can access confined spaces where people or larger robots are unable. As the scale of the robot decreases, the relative size of the environment increases; therefore, maintaining the mobility of the small-scale robot is required. However, small-scale robots have limitations in using a large number of high-performance actuators, powerful computational devices, and a power source. Insects can effectively navigate various terrains in nature with their legged motion. Discrete contact with the ground and the foot enables creatures to traverse irregular surfaces. Inspired by the leg motion of the insect, researchers have developed small-scale robots and they implemented swing and lifting motions of the leg by designing leg linkages that can be adapted to small-scale robots. In this paper, we propose a leg linkage design for insect-inspired small-scale ground mobile robots. To use minimal actuation and reduce the control complexity, we designed a 1-DOF 3-dimensional leg linkage that can generate a proper leg trajectory using one continuous rotational input. We analyzed the kinematics of the proposed leg linkage to investigate the effect of link parameters on the foot trajectory.

• 한국습지학회지
• /
• 제18권3호
• /
• pp.267-274
• /
• 2016

농촌 지역 하수도 보급은 하천, 호소 및 습지와 같은 수계 수질 보호를 위해서 반드시 필요하다. 또한 안정적인 소규모 하수처리장 운영을 위해서는 유입 유량과 농도의 변화가 큰 소규모 하수도 특성을 고려해야 한다. 본 연구에서는 봉화군 18개의 소규모 하수처리장 운전 결과를 통해 유입유량비 (유입 유량 / 설계 유량) 특성, 소규모 하수처리장 처리 효율에 미치는 영향과 적정 유입유량비 산정에 관한 연구를 수행하였다. 분석 결과 유입유량비는 여름철에 가장 높은 것으로 나타난 반면, 유입 하수 농도는 가을철과 겨울철에 높은 것으로 나타났다. 유입유량비가 증가할수록 처리 효율이 증가하는 경향을 보였으며, 영양염류 처리 효율이 유기물과 부유물질 처리 효율에 비해 민감한 영향을 받는 것으로 나타났다. 안정적인 소규모 하수처리장 처리 효율을 위해서는 유입유량비 0.8 이상을 유지해야 할 것으로 판단된다.

• 한국물환경학회지
• /
• 제34권2호
• /
• pp.226-233
• /
• 2018

Small-scale wastewater discharge facilities account for 98% of all workplaces, but in the generation and emission of major pollutants, they account for 27.5 % and 23.5 %, respectively. Since the proportion of the emission load of the small-scale workplace is not large, the national environmental policy has been established mainly around large-scale wastewater discharge facilities. However, in the case of specific hazardous substances in water, the amount of the discharge load of the small-scale wastewater discharge facility was 2.4 times higher than that of the generation load. Certain types of specific hazardous substances in water, which have a higher discharge load than large-scale wastewater discharge facilities, account for 24 ~ 32 %. There are also cases in which the discharge load from a small-scale discharge facility is more than four times higher, depending on the specific kind of water pollutant. As a result of inspections, the violation rate of the small-scale wastewater discharge facility among the total violations by facilities is 93.9 ~ 97.5 %. As a result, the ecotoxicity value of small-scale wastewater discharge facilities was high in most industries, and there was a fluctuation in the measured value. This indicates that the ecological integrity of the water system can be largely influenced by small-scale wastewater discharge facilities. Therefore, it is necessary to expand the environmental management of small-scale wastewater discharge facilities, and in some cases, the effect of the improvement in quality may be more significant than in the management of large-scale wastewater discharge facilities.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
• /
• pp.156-161
• /
• 2003

Mechanical behavior of rock joints usually can be characterized by small-scale laboratory shear tests due to economical and technical limitations, but their applicability to the behaviour of rock mass has been always questioned by a number of researchers because of scale effect. Though there have been several researches regarding the scale effect, it has been a controversial problem how to apply the result of small-scale laboratory shear test directly to field design from different conclusions among researchers. In order to grasp the trend of scale effect of shear behavior, a series of direct shear tests on replicas of natural rock joint surfaces made of gypsum cement with different size and roughness were conducted and analyzed. Result showed that as the size of the specimen increased, average peak shear displacement increased, but average shear stiffness and average peak dilation angle decreased. As for the dependency of scale on shear strength, the degree of scale effect was dependent on normal stress and roughness of rock joint. For the condition of low normal stress and high roughness, decrease of average peak shear strength with increasing size of joint was evident.

• 한국지반환경공학회 논문집
• /
• 제20권10호
• /
• pp.15-27
• /
• 2019

본 연구에서는 원통형 대책구조물의 설치조건에 따른 토석류의 에너지 저감효과를 분석하기 위해, 원통형 대책구조물을 설치 가능한 소형 수로를 제작하고 구조물의 종방향 설치 수를 변화시켜가면서 실내모형실험을 수행하였다. 또한 토석류와 대책구조물의 크기변화가 흐름특성에 미치는 영향을 확인하기 위해, 대형수로 내에서 소형수로 실험과 동일한 종방향 구조물을 배치하고, 토석류와 대책구조물의 크기를 증가시켜 실험을 수행하였다. 소형 및 대형수로 실험결과, 원통형 대책구조물의 설치 개수가 증가는 토석류의 유속과 흐름깊이를 감소시켜, 토석류의 에너지 저감효과를 증가시키는 것으로 나타났다.

• 전기학회논문지
• /
• 제59권3호
• /
• pp.499-505
• /
• 2010

This paper analyzed that the coordination of recloser-fuse when a superconducting fault current limiter (SFCL) is installed to a power distribution system linked small scale cogeneration system. As a rule, the recloser to properly protect against both permanent and temporary fault is installed to upstream of fuse. Therefore, in a power distribution system linked small scale cogeneration system, the fault current is increased by adding fault current of small scale Cogeneration system when a permanent fault occurs, and the fuse could melt during the first fast operation of the recloser because of more sufficient heat from the increased current. However, when SFCLs are applied into a power distribution system linked small scale cogeneration system, the coordination of recloser-fuse could be accomplished due to decreased fault current as the effect of the impedance value of the SFCL. Therefore, to solve these problems, we analysed the operation of recloser-fuse coordination in a power distribution system linked small scale cogeneration system with SFCL using PSCAD/EMTDC.

• 해양환경안전학회지
• /
• 제27권4호
• /
• pp.538-549
• /
• 2021

본 연구에서는 Froude 수 1.0으로 운항하는 길이 약 10m 급 소형 고속선박의 에너지 효율 설계를 위해 선미부에 트림 탭을 부착하였고, 선저 면과의 각도에 따른 항주자세와 저항성능의 변화를 살펴보았다. 성능 해석은 CFD 해석을 통해 수행되었으며, 축척에 의한 영향을 보기 위해 모형선과 실선에 대해 각각 해석을 수행 후 두 결과로부터 예측된 실선의 성능을 비교하였다. 나선에 대한 해석 결과는 두 결과가 전반적으로 유사하였고, 트림 탭이 부착된 경우 선저 면과의 각도가 동일할 때 자세 변화량이 달라 전 저항의 차이로 이어졌지만 자세에 따른 저항 변화 경향은 유사하였다. 이로부터 축척 효과가 있더라도 저항 저감 경향으로부터 최적 항주자세를 찾을 수 있으나, 트림 탭에 의한 자세 변화와 실선 주위 유동의 특성을 알기 위해서는 실선에 대한 직접적인 해석이 필요함을 알 수 있다.

• 대한화학회지
• /
• 제50권3호
• /
• pp.256-262
• /
• 2006

연구의 목적은 Small-Scale Chemistry(SSC)를 적용한 수업이 고등학생의 과학성취도 및 과학관련 정의적 특성에 미치는 효과를 알아보는 것이다. 이를 위해 제 7차 교육과정의 고등학교 과학 교과서 화학영역에 대한 SSC 실험 프로그램을 개발하였다. 실험집단에는 SSC 실험 프로그램을 적용하고 비교 집단에서는 교과서를 중심으로 한 전통적 실험 수업을 실시하여 사전-사후 과학성취도 및 과학관련 정의적 영역의 변화를 조사하였다. 연구결과에 의하면 SSC 실험 프로그램을 적용하여 수업한 실험집단의 성취도가 교과서 내용의 전통적인 실험수업을 실시한 비교집단에 비해 유의미하게 높았다(p<.01). 과학관련 정의적 영역의 경우, 흥미와 과학적 태도 영역에서도 SSC 실험집단이 비교집단에 비해 유의미하게 높은 것으로 나타났다(p<.05). 또한 SSC 적용 수업에 대한 학생들의 인식을 살펴본 결과 학생들은 대부분 과학학습에 있어 효과적이고 흥미 있는 수업이라고 응답하였으며, 과학성취도와 정의적 영역의 변화를 잘 설명해주고 있었다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
• /
• pp.125-128
• /
• 2006

Many research have been carried out concerned with the flexural performance of FRP composite in a various ways. Most of them, however, have used a small-scale specimen, so haven't been fully verified by full-scale model test. In this study, a full-scale RC beam model test for flexural strengthening with CFRP composites has been performed in order to verify test results obtained through a series of small-scale model test with respect to FRP stiffness affecting strengthening performance in the previous studies. A total of 4 specimens have been manufactured including control beam. The specimens strengthened with CFRP composites consist of 3 different CFRP stiffness with 2 types of CFRP composite. Consequently, the purpose of this study is to estimate influence of the size effect of specimens and FRP stiffness on the flexural performance. As a result, the effective strain of FRP composite is inversely proportional to FRP stiffness and ensures the same performance with small-scale model test.