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Sung-Cheoul Roh,강승희 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.11
This study investigates the effects of parameters such as a blade profile (changing the digit of the 4-digit NACA00xx airfoil), the Reynolds number, and the solidity on the performance characteristics of a straight bladed vertical axis wind turbine (VAWT). A numerical analysis, adopting the multiple stream tube (MST) method, is carried out to evaluate the performance depending on the parameters. The numerical result shows that the variation of a blade profile directly influences the power production, i.e., the high-digit NACA00xx airfoil provides higher power in a low speed zone (BSR < 3; BSR: blade speed ratio (ΩR/Uf), Ω: angular velocity of blade, R: radius of a straight Darrieus wind turbine, Uf: free stream velocity) than the low-digit NACA00xx profile. On the contrary, the low-digit NACA00xx airfoil produces higher power in a high speed range (BSR > 5) than the high-digit NACA00xx profile. An enhancement of the power production is observed with increasing the Reynolds number on the whole tested blade speed ratio range (1 < BSR < 12). In particular, the rate of the enhancement of the power is rapidly decreased with the increases of the Reynolds number (Re = ρŪrc/μ, ρ: air density, Ūr: mean resultant velocity acting on a blade with variable rotating speeds in a uniform free stream velocity (Uf), c: blade chord length, μ: air viscosity). For the effect of the solidity on the power production, a marked reduction of the range of the blade speed ratio that can provide the power is observed with increasing the solidity. A pattern of very steep variation of the power around the peak in the low speed zone (BSR < 3) is found in a high solidity range (σ > 0.3; σ: solidity (Nc/R), N: number of blade, c: chord length of an airfoil), and this tendency is conspicuously different from that of the eggbeater-type Darrieus VAWT, which is interpreted as a gradual variation of the power around the peak.
Patchable, flexible heat-sensing hybrid ionic gate nanochannel modified with a wax-composite.
Chun, Kyoung-Yong,Choi, Wook,Roh, Sung-Cheoul,Han, Chang-Soo RSC Pub 2015 Nanoscale Vol.7 No.29
<P>Heat-driven ionic gate nanochannels have been recently demonstrated, which exploit temperature-responsive polymer brushes based on wettability. These heat-sensing artificial nanochannels operate in a broad temperature-response boundary and fixed liquid cell environment, thereby experiencing limited system operation in the flat and solid state. Here we have developed a patchable and flexible heat-sensing artificial ionic gate nanochannel, which can operate in the range of the human body temperature. A wax-elastic copolymer, coated onto a commercial nanopore membrane by a controlled-vacuum filtration method, was used for the construction of temperature-responsive nanopores. The robust and flexible nanochannel heat sensor, which is combined with an agarose gel electrolyte, can sustain reversible thermo-responsive ionic gating based on the volumetric work of the wax-composite layers in a selective temperature range. The ionic current is also effectively distinguished in the patchable bandage-type nanochannel for human heat-sensing.</P>
실리콘 미세 가공을 이용한 열전형 미소유량센서 제작 및 특성
이영화 ( Young Hwa Lee ),노성철 ( Sung Cheoul Roh ),나필선 ( Pil Sun Na ),김국진 ( Kook Jin Kim ),이광철 ( Kwang Chul Lee ),최용문 ( Yong Moon Choi ),박세일 ( Se Il Park ),임영언 ( Young Eon Ihm ) 한국센서학회 2005 센서학회지 Vol.14 No.1
N/A A thermoelectric flow sensor for small quantity of gas flow rate was fabricated using silicon wafer semiconductor process and bulk micromachining technology. Evanohm R alloy heater and chromel-constantan thermocouples were used as a generation heat unit and sensing parts, respectively. The heater and thermocouples are thermally isolated on the Si₃N₄/ SiO₂/Si₃N₄ laminated membrane. The characteristics of this sensor were observed in the flow rate range from 0.2 slm to 1.0 slm and the heater power from 0.72 mW to 5.63 mW. The results showed that the sensitivities ((??(ΔV)/??(q)); AV : voltage difference, 4 : flow rate) were increased in accordance with heater power rise and decreasing of flow rate.