• Journal of the Korean Vacuum Society
• /
• v.22 no.5
• /
• pp.270-275
• /
• 2013

Single-layer graphene layers have been synthesized by using chemical vapor deposition, subsequently transferred on 300 nm $SiO_2/Si$ and quartz substrates, and doped with $AuCl_3$ by spin coating for various doping concentrations ($n_D$) from 1 to 10 mM. Based on the $n_D$-dependent variations of Raman frequencies/peak-intensity ratios, sheet resistance, work function, and Dirac point, measured by structural, optical, and electrical analysis techniques, the p-type nature of graphene is shown to be strengthened with increasing $n_D$. Especially, as estimated from the drain current-gate voltage curves of graphene field effect transistors, the hole mobility is very little varied with increasing $n_D$, in strong contrast with the $n_D$-dependent large variation of electron mobility. These results suggest that $AuCl_3$ is one of the best p-type dopants for graphene and is promising for device applications of the doped graphene.

• Journal of Wetlands Research
• /
• v.15 no.2
• /
• pp.251-264
• /
• 2013

There are some factors affecting the shorebirds in selecting a coastal inland roost site where they have to stay during the high tide when the entire intertidal zone is covered with water. We investigated eight species (Eastern Curlews Numenius madagascariensis, Green Shanks Tringa nebularia, Bar-tailed Godwits Limosa lapponica, Grey Plovers Pluvialis squatarola, Dunlins Calidris alpine, Whimbrels Numenius phaeopus, Eurasian Curlews Numenius arquata and Terek Sandpipers Xenus cinereus) to identify the spatial and temporal variability in coastal inland roost use in the area and the factors influencing the use. We considered the area and length of the standing water in the roost site, temperature, wind speed, the time of migration and the intensity of disturbance. As a result, number of individuals and type of species using the roost site varied across spatial and temporal scales. And the factors affecting the roost use was species-specific. The roost site of the study area was a closed shrimp farm however, it has been converted to a Salicornia herbacea, a salt marsh plant, farm recently. In a situation where coastal inland roost site is needed, we hereby describe a resolution for the juxtaposition of shorebirds and farming.

• Korean Journal of Materials Research
• /
• v.10 no.9
• /
• pp.629-635
• /
• 2000

The texture evolution during isothermal forging and subsequent heat treatment in Ti-48.5at%Al-0.6at%Mo alloy was investigated. Especially, in the present study, research interest was focused on the interrelation between lamellar volume fraction and textures varied with the change of heat-treated time and temperature. It was found that texture components having ND┴{302) and TD$\perp${100} with minor TD$\perp${111} were developed by isothermal forging. In addition, when the followed heat-treatment time and temperature increased from $1330^{\circ}C$/10h to $1350^{\circ}C$/20h respectively, both the lamellar volume fraction and the intensity of textures mentioned above also gradually increased. However, the tensile elongation at room temperature decreased oppositely, as the lamellar volume fraction increased. These results suggested that tensile properties of $\gamma$-TiAl with the nearly lamellar microstructure at room temperature were affected more strongly by the microstructural features such as lamellar volume fraction rather than by textures.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.138-152
• /
• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.7
• /
• pp.574-577
• /
• 2011

In this study, we use the $2.5cm{\times}7.5cm$ soda lime glass as the substrate. We used the ultrasonicator. Glass was dipped in the acetone, methanol and DI water respectively for 10 minutes. Ar(99.99%)gas was used as the sputtering gas. We varied the RF power between 100~175 W with 25 W steps. Base pressure was kept by turbo molecular pump at $3.0{\times}10^{-6}$ torr. Working pressure was kept by injection of Ar gas. ZnS thin films were deposited with the radio frequency magnetron sputtering technique at various temperatures and sputtering powers. It is also clearly observed that, the intensity of the (111) XRD peak increases with increasing the RF power. Electrical properties were measured by hall effect methods at room temperature. The resistivity, carrier concentration, and hall mobility of ZnS deposited on glass substrate as a function of sputtering power. It can be seen that as the sputtering power increase from 100 to 175 W, the resistivity of the films on glass decreased significantly from $8.1{\times}10^{-2}$ to $1.2{\times}10^{-3}\;{\Omega}{\cdot}cm$. This behavior could be explained by the effect of the sputtering power on the mobility and carrier concentration. When the RF power increases, the carrier concentration increases slightly while the resistivity decreases significantly. These variation originate from improved crystallinity and enhanced substitutional doping as the sputtering power increases.

• Korean Journal of Materials Research
• /
• v.12 no.6
• /
• pp.452-457
• /
• 2002

Titanium oxide films were prepared by RF reactive magnetron sputtering. The effect of sputtering conditions on structural and optical properties was investigated systemically as a function of sputtering pressure(5~20 mTorr) and $O_2/Ar$ flow ratio(0.08~0.4). The results of the X-ray diffraction showed that all films had only the anatase $TiO_2$ phase. At low sputtering pressure and $O_2/Ar$ flow ratio, the films had preferred orientations along [101] and [200] directions. As the sputtering pressure and $O_2/Ar$ flow ratio increased, the intensity of the 101 and 200 diffraction peaks decreased gradually. The microstructure of the sputtered films showed the fine grain size (20nm~50nm) and columnar microcrystals perpendicular to the substrate. With increasing the sputtering pressure and decreasing $O_2/Ar$ flow ratio, the sputtered films showed the more porous columnar structure. XPS analysis showed that stoichiometric $TiO_2$ films were deposited at 7 mTorr sputtering pressure and 0.2 $O_2/Ar$ flow ratio. The results of the X-ray diffraction showed that all films had only the anatase $TiO_2$ phase. Ellipsometeric analysis showed that the refractive index increased from 2.32 to 2.46 as the sputtering pressure decreased. The packing density calculated using the refractive index varied from 0.923 to 0.976, indicating that $TiO_2$films became denser as the sputtering pressure decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.264-264
• /
• 2010

Single-walled carbon nanotubes (SWCNTs) were grown on a Si wafer by using thermal chemical vapor deposition (t-CVD). We investigated the effect of the catalyst deposition rate on the types of CNTs grown on the substrate. In general, smaller islands of catalyst occur by agglomeration of a catalyst layer upon annealing as the catalyst layer becomes thinner, which results in the growth of CNTs with smaller diameters. For the same thickness of catalyst, a slower deposition rate will cause a more uniformly thin catalyst layer, which will be agglomerated during annealing, producing smaller catalyst islands. Thus, we can expect that the smaller-diameter CNTs will grow on the catalyst deposited with a lower rate even for the same thickness of catalyst. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. The catalyst layers were. coated by using thermal evaporation. The deposition rates of the Al and Fe layers varied to be 90, 180 sec/nm and 70, 140 sec/nm, respectively. We prepared the four different combinations of the deposition rates of the AI and Fe layers. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of $H_2$ as a carrier gas and 20 sccm of $C_2H_2$ as a feedstock at 95 torr and $810^{\circ}C$. The substrates were subject to annealing for 20 sec for every case to form small catalyst islands prior to CNT growth. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, UV-Vis NIR spectroscopy, and atomic force microscopy. The fast deposition of both the Al and Fe layers gave rise to the growth of thin multiwalled CNTs with the height of ${\sim}680\;{\mu}m$ for 10 min while the slow deposition caused the growth of ${\sim}800\;{\mu}m$ high SWCNTs. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of $113.3{\sim}281.3\;cm^{-1}$, implying the presence of SWCNTs (or double-walled CNTs) with the tube diameters 2.07~0.83 nm. The Raman spectra of the as-grown SWCNTs showed very low G/D peak intensity ratios, indicating their low defect concentrations.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.49 no.3
• /
• pp.53-61
• /
• 2012

This paper proposes a real-time distance measurement system of high temperature and high speed target using infrared stereo camera. We construct an infrared stereo camera system that measure the difference between target and background temperatures for automatic target measurement. First, the proposed method detects target region based on target motion and intensity variation of local region using difference between target and background temperatures. Second, stereo matching by left and right target information is used to estimate disparity about real-time distance of target. In the proposed method using infrared stereo camera system, we compare distances in three dimension trajectory measuring instrument and in infrared stereo camera measurement. In this experiment from three video data, the result shows an average 9.68% distance error rate. The proposed method is suitable for distance and position measurement of varied targets using infrared stereo system.

• Journal of the Microelectronics and Packaging Society
• /
• v.16 no.4
• /
• pp.33-39
• /
• 2009

A microlens array (MLA) was developed based on the wet-etched quartz substrate and coating of UV adhesive on the substrate for maskless lithography application. The developed MLA has the focal length of ${\sim}45\;{\mu}m$ and the spot size of ${\sim}1\;{\mu}m$. The spot size of the focused beam passing through the MLA was detected by CCD camera, and its intensity was monitored by beam profiler. Uniform spots with nearly identical intensities were observed on the focal plane when a beam passes through the fabricated MLA. The focal length was varied depending on thickness of the coated UV adhesive. The thicker the thickness of the UV adhesive was, the shorter the focal length of the MLA was. With a general mask aligner, UV beam focusing was tested onto photoresist (PR). The beams were well focused onto PR when UV passes through the MLA. Depending on the variable distances from the MLA, beam sizes onto PR were controlled. Even at high temperature for a long time, the performances of the MLA were not changed.

• Journal of Bio-Environment Control
• /
• v.4 no.1
• /
• pp.9-16
• /
• 1995

The effect of day and night temperature on the seedlings growth as well as physiological responses of red pepper seedlings to temperature, such as uptake of water and nutrients, rates of photosynthesis and respiration of leaf and root were also investigated in growth cabinet. The results obtained were as follows ; 1. As the temperature dropped down to 12$^{\circ}C$, the uptake of water and nutrients, nitrate, phosphorus and potassium were decreased drastically. At 5$^{\circ}C$ there was virtually no uptake of water and nutrients. 2. Photosynthetic activity in the leaves of red pepper seedlings was increased gradually from 5$^{\circ}C$ to $25^{\circ}C$ and observed the highest photosynthetic activity at $25^{\circ}C$, but respiratory activity of leaf increased up to 3$0^{\circ}C$ and the same trend was observed in root respiratory activity. 3. Optimal combination of day and night temperature for shoot dry weight which is the decisive criterion of good seedlings of red pepper was found to be $25^{\circ}C$ at nighttime and 3$0^{\circ}C$ at daytime and then day/night temperature showed in the order of 25/25, 30/15, 15/25, 10/$25^{\circ}C$. No increment of shoot dry weight at 5$^{\circ}C$ in nighttime temperature observed regardless of daytime temperature.