• Proceedings of the Korean Vacuum Society Conference
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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.

• Korean Journal of Optics and Photonics
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• 제9권4호
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• pp.258-263
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• 1998

Quasi-elastic light scattering is utilized to measure the mean diameter of the 0.3 $\mu\textrm{m}$-dimeter polystyrene sphere. The mean diameter of the polystyrene sphere is required to be known within the uncertainty of a few per centages. The systematic error has been considerably reduced by improving the system for the angle alignment and temperature measurement of cell. NIST SRM 1691 (0.269$\pm$0.007 $\mu\textrm{m}$: TEM; 0.275$\pm$0.007 $\mu\textrm{m}$: QELS) is measured to be 0.273 $\mu\textrm{m}$$\pm$0.006 $\mu\textrm{m}$ in mean diameter. Detailed description is given of the improved method and the resultant uncertainty, and the comparison of results with NIST is followed.

• Journal of Veterinary Clinics
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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.

• Journal of the Korean Geotechnical Society
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• 제16권1호
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• pp.43-50
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• 2000

In this paper, the consolidation efficiency and the equivalent diameter of the cross shaped drain are examined by using the laboratory test and the numerical model, and the results are compared with those of the band shaped drain. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The efficiency of the cross shaped drain is evaluated by using the 3-D flow program which was validated by the settlement-time test fill data. The results of laboratory test show that the equivalent diameter of the band shaped drain was close to the Rixner's formula and that of the cross shaped drain was fit to the following formula: $d_w\;=\; \\tarc{3}{4}.(b+t)$The results of the numerical analysis show that the cross shaped drain can reduce the consolidation time by 9-10% from that for the band shaped drain. The equivalent diameter obtained from the numerical flow model by using the field data is 3.5 times smaller than that obtained from the laboratory consolidation test.

• Journal of Animal Environmental Science
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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.

• The KSFM Journal of Fluid Machinery
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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.

• Journal of the Korean Society of Manufacturing Technology Engineers
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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.