• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.286-286
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• 2010

The lack of homogeneously sized single-walled carbon nanotubes (SWNTs) hinders their many applications because properties of SWNTs, in particular electrical conduction, are highly dependent on the diameter and chirality. Therefore, the preferential growth of SWNTs with predetermined diameters is an ultimate objective for applications of SWNTs-based nanoelectronics. It has been previously emphasized that a catalyst size is the one crucial factor to determine the CNTs diameter in chemical vapor deposition (CVD) process, giving rise to several attempts to obtain size-controllable catalyst by diverse methods, such as solid supported catalyst, metal-containing molecular nanoclusters, and nanostructured catalytic layer. In this work, diameter-controlled CNTs were synthesized using a nanostructured catalytic layer consisting of Fe/Al2O3/Si substrate. The CNTs diameter was controlled by structural modification of Al2O3 supporting layer, because Al2O3 supporting layer can affect agglomeration phenomenon induced by heat-driven surface diffusion of Fe catalytic nanoparticles at growth temperature.

• 한국광학회지
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• 제9권4호
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• pp.258-263
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• 1998

준탄성광산란(QELS)을 이용하여 지름이 0.3$\mu\textrm{m}$인 폴리스티렌구의 평균지름을 측정하였다. 폴리스티렌구가 표준입자로 사용되기 위하여는 평균지름의 불확도가 수 % 이내가 되어야 한다. 본 연구에서는 QELS장차중 시료용기의 정렬방법 및 온도측정방법을 특별히 보완하여 계통오차를 대폭 줄였다. 표준입자 인증물질인 NIST SRM 1691 (0.269$\pm$0.007$\mu\textrm{m}$: TEM; 0.275$\pm$0.007$\mu\textrm{m}$:QELS)을 측정하여 평균지름이 0.2730.006$\mu\textrm{m}$ 인 결과를 얻었다. 개선된 측정방법 및 측정불확도를 상세히 기술하였으며 NIST의 측정결과와 비교하였다.

• 한국임상수의학회지
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• 제21권2호
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• pp.143-148
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• 2004

Serial ultrasonographic examination was daily performed on 12 pregnant Shih-tzu bitches from day 15 until parturition to determine the size of gestational structures. Gestational age was timed from the day of ovulation (day 0), which was estimated to occur when plasma progesterone concentration was first increased above 4.0 ng/ml. Extra-fetal structures were measurable from days 17 to 46. Outer uterine diameter increased from $9.9{\pm}0.4$ mm (Mean${\pm}$SD) at day 20 to $44.3{\pm}0.8$ mm at day 46 and inner chorionic cavity diameter increased from $7.2{\pm}0.2$ mm at day 17 to $36.9{\pm}1.5$mm at day 41. Length of chorionic cavity or zonary placenta increased from $6.6{\pm}0.4$ mm at day 21 to $46.4{\pm}0.9$ mm at day 44. Of the extra-fetal structures, inner chorionic cavity diameter was the most accurate for estimation of gestational age until day 38. Fetal structures were measurable from days 23 to 60. Crown-rump length increased from $3.9{\pm}0.3$ mm at day 23 to $55.2{\pm}3.3$ mm at day 41, fetal body diameter increased from $7.9{\pm}0.6$ mm at day 32 to $47.8{\pm}2$ mm at day 60, and fetal head diameter increased from $6.3{\pm}1.1$ mm at day 29 to $25.6{\pm}0.2$ mm at day 60. Of the fetal structures, fetal head diameter was the most accurate for estimation of gestational age from day 38 until day 60.

• Journal of Biosystems Engineering
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• 제4권2호
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• pp.46-52
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• 1979

The water delivery hose for agricultural pump is getting popular in rural areas in korea. Friction head loss, discharge, and power requirements were measured in various discharge for different material and diameter of hose to get basic data for economical use in agricultural pump. The results attained in this study were as follows ; 1. Friction head loss increased significantly as the velocity increased, and the difference of velocity between the different diameter of hose was bigger than that between materials, which was resulted in the increase of the friction head loss. 2. Friction head loss in the case of that the velocity with 2m/sec was constant was about 3.53 to 4.01 m/100m in the diameter 3" and about 2.30 to 3.10 m/100m in the diameter 4". Material A of diameter 3" showed the maximum value 8.4m/100m in Reynolds number $2.0\times10^5$, 4" got the minimum value 2.24m/100m, the difference between these values was bigger than 6m per 100 meters in the friction head loss. 3. Darcy-Weisbach formular with friction coefficient [f] calculated by Nikurades formular in the smooth pipe or with friction coefficient [f] calculated on the base of C value 125 in Hazen-Williams formular was available in friction head loss of the water discharger hose in rural areas. 4. Total head increased as friction head loss increased , meanwhile total discharge decreased, and 20 percents of energy was more saved in Material C 4″pipe than Material A 3″pipe in the view point from the discharge per unit power requirement, this phenomenon suggested that long distance pipe would be advantage in larger diameter pipe for save of energy. for save of energy.

• 한국지반공학회논문집
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• 제16권1호
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• pp.43-50
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• 2000

본 논문은 실내시험과 수치모델을 이용하여 십자형 배수재의 압밀촉진효과와 등가직경을 검토하고 판형배수재와 비교하였다. 배수재의 등가직경은 실내시험으로부터 역계산하여 문헌에 의해 제시된 공식으로부터 산정된 결과와 비교하였고, 압밀효과는 3차원 흐름해석프로그램인 MODFLOW를 사용하였다. 해석모델의 신뢰성은 현장의 침하-시간 계측자료를 이용하여 검토하였다. 실내시험결과 산정된 판형 배수재의 등가직경은 Rixner의 제안식에 유사한 경향을 보였고, 십자형 배수재의 등가직경은 $d_w\;=\; \\tarc{3}{4}.(b+t)$로 산정되었다. 실제현장을 모델링한 수치해석결과 십자형 배수재는 압밀시간이 9-10% 감소하였고, 현장자료를 이용한 수치 흐름모델로부터 산정한 등가직경은 실내시험보다 3.5배 작은 것으로 나타났다.

• 한국축산시설환경학회지
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• 제4권2호
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• pp.127-136
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• 1998

To use the earth heat for the livestock housing, an underground heat exchanger is developed and pipes are layed in the depth of 2.5m under the ground. The pipes have two different kinds of diameter (200mm, 100mm) and materials (PE, PVC). The results of heating effect in winter and spring are following. The temperature in different soil depth varies from 5$^{\circ}C$ by 1.5m depth, to 9$^{\circ}C$ by 3.5m. So it should be better to have the depth greater than 2.5m. The difference of air temperature between the inside and outside pipe was 9.9 Kelvin(K) with 200mm diameter and 13.4K with the 100mm diameter with the same material in winter. By the lower outside temperature from -7.2$^{\circ}C$, it could keep the air temperature above 6$^{\circ}C$ through the 100mm diameter pipe. The heating performance was 593 W with 200mm diameter, 118W with 100mm diameter (PE), and 115W with 100m diameter (PVC), respectively. As the outside temperature varies from -1.5$^{\circ}C$ to 18.6$^{\circ}C$ in early spring, the air temperature through the pipes show 4∼8$^{\circ}C$. While the difference between maximum and minimum outside temperature is 14K, the one through the pipes could be reduced by 2K. Pipes with small diameter can more reduce the difference than the pipe with larger diameter.

• Journal of Advanced Marine Engineering and Technology
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• 제28권1호
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• pp.29-38
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• 2004

The Condensation heat transfer coefficients of R-22 and R-l34a were measured in smooth horizontal copper tubes with inner diameters of 1.77. 3.36 and 5.35 mm. respectively. The experiments were conducted in a closed loop. which was driven by a magnetic gear pump. They were Performed for the following ranges of variables: mass flux (200 to $500\;kg/\textrm{m}^2{\cdot}s$) saturation temperature $30^{\circ}C$ and quality (0 to 1.0). The main results obtained are as follows Condensation heat transfer coefficients in the small diameter tubes (ID < 7 mm) were observed to be strongly affected by inner diameter change and to differ from those in the large diameter tubes. The heat transfer coefficients in the small diameter tubes were 20 ~ 40 % higher than those in the large diameter tubes as the inner diameter of the tube was reduced. Also. it was very difficult to apply some well-known previous predictions (Cavallini-Zecchin's. Haraguchi's and Dobson's correlation) to small diameter tubes. Based on an analogy between heat and mass transfer the new correlation is Proposed to predict the experimental data more accurately.

• 한국유체기계학회 논문집
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• 제19권1호
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• pp.45-51
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• 2016

This study conducted CFD analysis on the mean velocity vector of distribution of the ejector driven pipe while changing the inlet velocity to 1 m/s at the diameter ratio of diffuser of 1:3, 1:2.25, 1:1.8 with the end position of driven pipe at 1, 1.253, 1.333, 1.467 respectively, which used $k-{\varepsilon}$/High Reynolds Number for the turbulence model, SIMPLE method for the analysis algorithm, and PIV experiment to verify the CFD analysis. As a result of the CFD analysis the optimum diameter ratio of ejector driven pipe was 1:3, the optimum end position of driven pipe was 1.333 for the diameter ratio of 1:3, 1:2.25, 1:1.8 and the PIV experiment obtained the same result as the CFD analysis. Therefore, the numerical analysis of the flow characteristics of ejector can be used for the optimum design implementation on ejector system.

• Transactions on Electrical and Electronic Materials
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• 제14권3호
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• pp.156-159
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• 2013

The electrical properties of ZnO nanowire field effect transistors (FETs) have been investigated depending on various diameters of nanowires. The ZnO nanowires were synthesized with an Au catalyst on c-plane $Al_2O_3$ substrates using hot-walled pulsed laser deposition (HW-PLD). The nanowire FETs are fabricated by conventional photo-lithography. The diameter of ZnO nanowires is simply controlled by changing the thickness of the Au catalyst metal, which is confirmed by FE-SEM. It has been clearly observed that the ZnO nanowires showed different diameters simply depending on the thickness of the Au catalyst. As the diameter of ZnO nanowires increased, the threshold voltage of ZnO nanowires shifted to the negative direction systematically. The results are attributed to the difference of conductive layer in the nanowires with different diameters of nanowires, which is simply controlled by changing the catalyst thickness. The results show the possibility for the simple method of the fabrication of nanowire logic circuits using enhanced and depleted mode.

• 한국생산제조학회지
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• 제21권3호
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• pp.415-420
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• 2012

Dust collecting performance of axial-vane type cyclone for oil mist was analyzed in this study. For predicting cut diameter size of cyclone, the number and angle of vane (${\beta}_2{^{\prime}}$) was calculated by CFD. As the result, ${\beta}_2{^{\prime}}$ was decreased as the number of vane was increased and the angle of inclination (${\beta}_2{^{\prime}}$) decreased, and it cause strong swirl flow. Therefore, it could be confirmed that as the number of vane was increased and the angle of inclination was decreased, cut diameter size was decreased. Also, by verifying the results of CFD through experiment, the cut diameter size could be 2 ${\mu}m$ at 4 $m^3/min$ of flow rate.