1,722,953 research outputs found
A novel design for an RF MEMS resistive switch on PCB substrate
No full textCopyright @ 2008 Stimulation Action on MEM
나노유체를 이용한 수조비등에서의 임계열유속 증진에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 원자력및양자공학과, 2009.2, [ x, 108 p. ]The understanding of CHF phenomenon and an accurate prediction of the CHF condition are important for safe and economic design of many heat transfer units including nuclear reactors, fossil fuel boilers, fusion reactors, electronic chips, etc. The phenomenon has been investigated extensively over the world since Nukiyama (1934) first characterized it. In particular, a large amount of significant work has been done during the last four decades with the development of water cooled nuclear reactors.
The wettability of the heated surface under pool boiling of surfactant solutions and nano-fluids has been investigated. Tri-sodium phosphate (TSP, ) solutions and Aluminum oxide nano-fluids were prepared for experiments. Contact angles of pure water and the solutions on the quenched surface and fresh surface were measured. Surfaces deposited TSP and nano-particle could affect surface energy of the strips and enhance hydrophilicity of the surfaces. Several implications of the experimental results on the pool boiling CHF model and CHF enhancement using TSP and NF were discussed.
A increase of CHF was observed with nano-fluid. The addition of nano-particle helped to increase the wettability by reducing the surface tension. This happens with the decrease in bubble diameter, breakup of bubbles and avoidance of bubble coalescence. CHF increase or decrease depends upon competition between high wettability and high instability. An optimum nano-fluid concentration is needed which must have high crystalline content. When the concentration reaches at a critical value, CHF will tend to a constant value.
As the results of previous study, surface tension effect the results of CHF. And it is same to nano-fluids, because surface tension change the dynamics of mixture fluids at two phase and means the instability of thermal hydraulics. Contact angle which be in the limelight at recent research means wettability of heated surface. However, in case of nano-fluids, both...한국과학기술원 : 원자력및양자공학과
A Mechanical Mimicry of the Negative Stiffness and Adaptation Mechanism of Stereocilia Bundle
No full textMechanical modeling of stereocilia's amplifying mechanism by combining negative stiffness and adaptation
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2011.2, [ v, 40 p. ]자연의 기본적인 감각 수용 기관인 유모세포는 기존 센서의 설계시 상충 관계에 있는 고감도와 광대역의 특성을 모두 가지고 있다. 자연은 반강성 메커니즘과 적응 메커니즘을 통해 이러한 특성을 갖는다. 반강성 메커니즘은 팁링크라는 단백질에 의해 이온 채널이 열리는 현상으로 인해 일어나는 현상이며 작은 신호에 대한 증폭 현상을 수반한다. 적응 현상은 섬모 번들의 위치를 적응 모터를 움직임으로써 조절해 주며 반강성 영역을 조절해 주는 역할을 한다. 이 두 메커니즘을 통해 섬모 번들은 고감도 광대역의 특성을 갖게 된다. 섬모 번들의 이런 메커니즘을 기계적인 시스템으로 모사한 연구는 현재까지 알려진 바가 없으며 본 연구에서는 섬모 번들의 두 증폭 메커니즘을 효과적으로 모사할 시스템을 제안하였다. 모델은 자석의 척력을 이용해 반강성 메커니즘을 구현한 부분과 스텝 모터를 사용해 자석을 움직여 반강성 영역을 조절하는 적응 메커니즘 부분으로 구성되어 있다. Displacement clamping 실험을 통해 제안한 모델이 반 강성의 특성을 가지며 자석이 움직임에 따라 반강성 역역이 이동하는 적응 현상을 확인 할 수 있었다. 이러한 모델은 최대 증폭과 강성 유지가 동시에 필요한 피에조 구동기 등의 기계적 설계 문제를 해결 할 수있는 기초 연구가 될 것으로 예상된다.한국과학기술원 : 기계공학전공
동위원소를 이용한 원자력 배터리 개발
No full text학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2004.2, [ vii, 43 p. ]Until now, the development of the useful microelectromechanical systems has the problems because previous batteries (solar, chemical, etc) did not satisfy the requirements related to power supply. At this point of time, nuclear battery using isotope sources is rising the solution of this problem. Nuclear battery can provide superior out-put power and lifetime. So a new type of micro power source (nuclear battery) for microelectromechanical systems has been designed and analyzed. In this work, I designed the three parts, isotope source, conversion device, and shielding. I chose suitable sources, and designed semiconductor using the chosen isotope sources. Power is generated by radiation exciting electrons in the semiconductor depletion region. The efficiency of the nuclear battery depends upon the pn-junction. In this study the several conceptual nuclear batteries using radioactive materials are described with pn-junction. And for the safety, I designed the shielding to protect the environment by reducing the kinetic energy of beta particles.한국과학기술원 : 원자력및양자공학과
Epidemiologic study of in-hospital cardiopulmonary resuscitation among pediatric patients: A retrospective, population-based cohort study in South Korea
No full textWe aimed to examine the clinical trends of in-hospital cardiopulmonary resuscitation (ICPR) and factors associated with live discharge following ICPR. As a national population-based cohort study, data were extracted from the South Korean National Inpatient Database. This study included 8992 pediatric patients under 18 years of age who underwent ICPR due to in-hospital cardiac arrest during hospitalization in South Korea between 2010 and 2019 (10 years). The annual prevalence, survival, duration of hospitalization, and total cost of hospitalization at ICPR were examined as clinical trends. In 2010, 7.94 per 100,000 pediatric patients received ICPR; the prevalence increased to 11.51 per 100,000 pediatric patients in 2019. The 10-year survival rates were similar, and the in-hospital, 6-month, and 1-year survival rates over 10 years were 44.0%, 34.0%, and 32.4%, respectively. The mean length of hospital stay at ICPR in 2010 was 20.7 (95% confidence interval [CI]: 19.3-22.2) days; this decreased to 16.6 (95% CI: 15.2-18.0) days in 2019. The mean total cost at ICPR was 11,081.1 (95% CI: 10,216.2-11,946.1) United States Dollars (USD) in 2010; this increased to 22,629.4 (95% CI: 20,588.3-24,670.5) USD in 2019. The prevalence of ICPR increased among pediatric patients in South Korea between 2010 and 2019; however, the survival rates were similar for the 10 years. The length of hospital stay at ICPR gradually decreased from 2010 through 2019, while the total cost of hospitalization at ICPR has gradually increased between 2010 and 2019.N
Specific Interactions of the –8 and –7 Base Pairs of Phage SP6 Promoter with Its RNA Polymerase
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