Drag and heat-flux assessment of hypersonic flow on an asymmetric blunt shaped body

Ikhyun Kim,Keunyeong Kim,Sangha Park,Byungkook Jang,Gisu Park,Gi-Hyuk Choi 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

Assessment of aerodynamic forces and heat-transfer rates for certain flight conditions is an essential task in designing a hypersonic vehicle. Experimental investigation of impulse ground-based type facilities is researchers standard practice for such purposes. However, due to extremely short test times of the flow, measurement of aerodynamic forces and heat-transfer rates in such facilities causes many technical issues. This study presents a series of drag and heat-flux measurements taken in the shock tunnel. An asymmetric blunt shaped forebody was tested at a nominal Mach 6. A conventional accelerometer-based drag balance system was applied to the test model during force measurements. K-type thermocouple sensors were used to measure surface heat-transfer rates. A comprehensive procedure for implementation and calibration of each measurement technique is provided in a single manuscript.

프리캐스트 모듈 바닥의 동하중 재하시험

Ikhyun Sung 한국재난정보학회 2017 한국재난정보학회 논문집 Vol.13 No.1

본 연구에서 프리캐스트 바닥판 위를 이동하는 차량하중에 의한 바닥판 접합거동을 파악하고자 하였다. 하중 재하를 위하여 프레임을 제작하였고 각 측정 장치를 활용하여 거동을 파악하였다. 바닥판의 정적응답을 검토하여 이론값과 비교하였고 그 특성은 매우 합리적임을 알 수 있었다. 또한, 동적영향 평가를 위하여 가속도, 속도 및 변위를 측정하여 시험에서 이동하중의 특성을 분석하였다. 이동하중에 의한 동적응답을 위하여 바닥판 진동수를 측정하였는데 하중의 범위에 대하여 진동의 특성은 민감하다고 판단되었다. 결과적으로 연결부의 동적 응답은 연결방법에 따라 특성이 다르므로 설계에 주의를 기울여야 할 것으로 판단되었다. In this study, we tried to understand the panel joint behavior by the vehicle load moving on precast panel. The frame was made for loading and the behavior was determined by using each measuring device. The static response of the panel was examined and compared with the theoretical value, and it was found that the characteristics were very reasonable. In addition, acceleration, velocity, and displacement were measured for dynamic impact evaluation, and the characteristics of moving load were analyzed in the test. The vibration frequency of the panel was measured for the dynamic response by the moving load, and the vibration characteristic was considered to be sensitive to the range of the load. As a result, it is considered that the dynamic response of the connection part should be careful in design because the characteristics are different according to the connection method.

레진으로 접착 보강한 강재보의 거동

Ikhyun Sung 한국재난정보학회 2017 한국재난정보학회 논문집 Vol.13 No.1

본 연구에서 강재 보와 보강을 위하여 부착한 탄소섬유판의 동일거동을 분석하기 위하여 시험 체를 제작하여 시험한 결과와 유한요소해석을 통한 분석을 실시하였다. 현재 국내외의 연구에서는 복합재료를 사용한 보수 보강 복구에 대한 사용검토가 많이 연구되어지는 실정에서 섬유보강 복합재료는 얇고 강도가 좋으며 가벼워 구조물의 보강 시에 사하중의 증가를 발생시키지 않고 부재의 치수 증가에도 영향이 없어 매우 유용한 재료로 부각된다. 그러나 노후화에 따른 부착력 저하 등의 문제와 경제성 및 설계상의 어려움으로 사용이 극히 제한적인 부분이다. 연구에서는 미래에 사용될 수 있다면 좋을 기초자료로써 단순한 빔에 탄소섬유판을 부착하여 성능을 평가하였다. 노후화를 고려하지는 못하였으나 부착성능 측면에서는 양호한 사용성능을 가진다고 판단되어진다. In this paper, the behaviour of composite steel-CFRP members is studied experimentally and using FE-analysis. The use of advance composite materials in construction for repair and rehabilitation has become a frequent used method in the last decade. FRP composites have many advantages over the traditional technique of steel bonding for a number of reasons: 1. Composites add little or no additional weight to a building, eliminating the need for costly foundation strengthening. 2. FRP composites are very thin (1.2mm to 1.4mm). So there is no loss of floor space and negligible effect over the architectural aspect. 3. FRP composites do not corrode, this makes it long lasting. However, the method is yet to become a mainstream application due to a number of economical and design related issues. Brittle de-bonding failure, aging effect on bonding, broad based awareness and proper design guidelines are the main concern for future research works. This paper is focused on the ultimate load carrying capacity of the CFRP-strengthened beams and their effect on the deflection and failures modes by varying the amount of CFRP content.

Development of GaN Memory for Harsh Environment Operation

Ikhyun Kwon,Il Hwan Cho 대한전자공학회 2015 ITC-CSCC :International Technical Conference on Ci Vol.2015 No.6

카이로프렉틱 교정을 사용한 요추의 교정시 남성과 여성 시술자의 최대 힘의 차이에 관한 고찰

IkHyun Jeon,HanSuk Jung,JooHyun Ham,JinOk Choi1․,JuWon Lee 한서대학교 보완대체의학연구소 2017 Research Journal of Complementary and Alternative Vol.- No.8

롤빔에 카본플레이트를 보강한 강재의 일체적거동 및 강성보강효과

IkHyun Sung 한국재난정보학회 2013 한국재난정보학회 논문집 Vol.9 No.4

본 연구에서는 기존구조물에 대한 보수와 복구에 보강을 위하여 복합재료의 사용이 증가하고 있는 상황에서 방재의 개념에도 부합하는 탄소섬유보강재를 이용하여 기존금속재와 접합(접착방식)을 통한 강도증진효과를 연구하였다. 특히 실험을 통하여 강-탄소섬유보강재로 이루어진 복합재 거동을 파악하였으며 여기에 적절한 시험을 위한 새로운 형태의 시험편을 제작하였다. 접합재로 레진을 도포하는 방법을 달리하고 거동을 비교하기 위하여 표면처리가 다른 시험편을 각각 고려하여 시험한 결과 강성보강효과는 물론 일체거동의 특성이 잘 나타남을 알 수 있었다.

Overview of Flow Diagnosis in a Shock Tunnel

Ikhyun Kim,Sungmin Lee,Gisu Park,Jong Kook Lee 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.3

In this work, an overview of flow diagnosis in a shock tunnel is made by means of using established techniques that are easy to setup, economical to arrange, and simple to measure. One flow condition was considered having Mach number of 6 at the nozzle-exit, regarded as freestream. Measured aerothermodynamic data such as shock wave speed, wall static and total pressures, surface heat flux, and shock stand-off distance ahead of test model showed good agreement with calculation. This study shows an overall procedure of flow diagnosis in a shock tunnel in a single manuscript. Outcomes are thought to be useful in the field of education and also in a preliminary stage of high-speed vehicle design and tests, that need to be performed within a short time with decent accuracy.

Two Options and One Choice: Diffusion of the Wage Peak System Across Workplaces in South Korea

Ikhyun Joo,Kyungmin Baek 서울대학교 사회발전연구소 2023 Journal of Asian Sociology Vol.52 No.3

In South Korea’s super-aged society, an aging workforce and the shortage of a younger workforce is leading toward a labor shortage as population aging and low fertility rates accelerate. To ensure sufficient workforce capacity, a labor policy called the “wage peak system has spread across workplaces in South Korea. The wage peak system can be implemented in two ways, referred to herein as Type 1 and Type 2, and organizations can adopt either to conform to institutional pressures. This study examines the diffusion of the wage peak system across workplaces and the different motivations to adopt either type. The study used data from the Korean Workplace Panel Survey conducted between 2005 and 2019. The results showed that institutional contexts had a strong influence on the spread of the wage peak system in South Korea. This study has implications for the ways organizations choose to implement systems, depending on the institutional context and several other factors.

Experimental investigation of the effects of leading edge bluntness on supersonic flow over a double compression ramp

Ikhyun Kim,박기수,Yunghwan Byun 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.10

Understanding the flow characteristics over a double compression ramp is crucial for high-speed vehicle design. Leading edge bluntness is a key factor influencing the formation of a separation region on a double compression ramp flow. In the present study, the effect of bluntness on a double compression ramp is investigated experimentally at a nominal Mach number of 4. The test model has 13º and 40º inclinations with respect to the freestream. Five different levels of leading-edge radius, varying from 0.0 to 2.0 mm, were subjected to supersonic wind tunnel tests. Shadowgraph and infrared thermography techniques were employed to visualize the flow features of the double ramp model. Measurements of surface heat-transfer along the centerline of the test model were obtained from the acquired infrared images. It is shown that the leading-edge radius alters the separation characteristics as well as the surface heat-transfer. Possible reasons for such flow characteristics are discussed.

Pediatric tetrasomy 18p presenting as a spastic cerebral palsy: A case report

Ikhyun Lim,Sang Hee Park,서미리,Hyunseok Kwak,Wookyung Park,심성한,김민영 대한의학유전학회 2021 대한의학유전학회지 Vol.18 No.2

Tetrasomy 18p is a genetic syndrome caused by an isochromosome consisting of two copies of the short arm of chromosome 18. Clinically, pediatric cases of tetrasomy 18p manifest with global developmental delay, similar to most cases of chromosomal abnormality. In addition, it causes various symptoms including abnormal muscle tone. We report a case of an infant with global developmental delay and remarkable spasticity, the typical phenotype of bilateral spastic cerebral palsy. However, she had a subtle anomaly in her face, and brain magnetic resonance imaging (MRI) findings were inconsistent with her strong upper motor neuron signs. Upon genetic testing, she was determined to have an 18p isochromosome, confirming de novo non-mosaic tetrasomy 18p. Cerebral palsy is a neurological disorder that includes developmental delay caused by a non-progressive lesion in the developing brain. During diagnostic workup in patients with cerebral palsy, genetic testing should be considered when there are minor physical anomalies or equivocal MRI findings.