• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.239.1-239.1
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• 2011

Dye sensitized solar cells (DSC) are promising devices for inexpensive, nontoxic, transparent, and large-scale solar energy conversion. Generally thick $TiO_2$ nanoporous films act as efficient photoanodes with their large surface area for absorbing light. However, electron transport through nanoparticle networks causes the slowdown and the loss of electron transport because of a number of interparticle boundaries inside the conduction path. We have studied DSCs with precisely dimension-controlled $TiO_2$ nanotubes array as photoanode. $TiO_2$ nanotubes array is prepared by template-directed fabrication method with atomic layer deposition. Well-ordered nanotubes array provides not only large surface area for light absorbing but also direct pathway for electrons with minimalized grain boundaries. Large enlongated anatase grains in the nanotubes could enhance the conductivity of electrons, but also suppress the recombination with holes through defect sites during diffusion into the electrode. To study the effect of grain boundaries, we fabricated two kinds of nanotubes which have different grain sizes by controlling deposition conditions. And we studied electron conduction through two kinds of nanotubes with different grain structures. The solar cell performance was studied as a function of thickness and grain structures. And overall solar-to-electric energy conversion efficiencies of up to 7% were obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.393-396
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• 2000

Spent fuel rod cutting device should cut a spent fuel rod to an optimal size in order to fast decladding operation. In this paper, for developing spent fuel rod cutting device with cutter blade, rod properties such as dimension and material of zircaloy tube and fuel pellet are investigated at first and then, various methods of existing cutting devices used commercially are investigated and their performance are analyzed and compared. This device is designed to be operated automatically via remote control system considering later use in Hot-Cell (radioactive area) and the mdularization in the structure of this device makes maintenance easy. SUS and Zircaloy-4 are selected as cut material used in the test of spent fuel rod cutting device by cutter blade. In order for constructing the high durable cutter blade, various materials are analyzed in terms of quality, shape, characteristic, and heat treatment, etc. and from these results, spent fuel rod cutting device is designed and manufactured based on the considerations of durability, round shape sustainability of rod cross-section, debris generation, and fire risk, etc.

• Journal of Plant Biology
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• v.34 no.1
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• pp.9-18
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• 1991

This study deals with the effect of dwarf growth on xylem structure, especially on the dimension of xylem elements described for 12 species of naturally occuring dwarf trees. The length and tangential diameter of tracheary elements and fibers in dwarf trees appear to be shorter and narrower than those in normal trees. Radial width and cell number of the same annual rings are narrower and smaller in dwarf trees than those in normal trees. Height of rays in dwarf trees is lower than that in normal trees. Dwarf conifers appear to have higher ratio, of latewood to earlywood than that in normal trees. In the hardwood species studied, mesomorphy of vessel elements is lower in dwarfs than that in normal trees. It can be concluded that this dwarf growth occurs as a result of extremely slow growth by environmental stress such as water deficiency.ciency.

• Journal of Navigation and Port Research
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• v.33 no.6
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• pp.451-456
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• 2009

In this paper, we presents an algorithm which generates its high-resolution DTM using a low-resolution DTM of the sea floor terrain and fractal theory. The fractal dimension of each patch region divided from the DTM is extracted and then with this information and original data, each cell region in the patch is interpolated using the midpoint displacement method and a median filter is incorporated to generate natural and smooth sea floor surface. The effectiveness of the proposed algorithm is tested on a fractal terrain map.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.1-7
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• 2005

To resolve some of the most pressing uncertainties of Peridinium identity, morphological characteristics of Korean Peridinium were examined using light and scanning electron microscopy. The Peridinium samples were collected from three different regions of Juam, Sang-sa and Togyo Reservoirs, when seasonal blooms occurred. Formula of the epithecal plate was recorded with 7 precingular, 3 intercalary, and 4 apical plates (4', 3a, 7"). An apical pore, 3 ${\sim}$ 5 ${\mu}m$ in size, was apparently present. The cingulum was easily observed under light microscope, and was considerably offset by about 15 ${\mu}m$ (2 ${\sim}$ 3 times per cingulum width). The sulcus was straight longitudinally and widened apparently towards the antapex. None of spine was found on the surface of the thecal plates on scanning electron micrographs. The average body length was 50.4 ${\mu}m$ with a range of 29 ${\sim}$ 63 ${\mu}m$. The geometric dimension, as designated to the body length:width ratio, was found from calculation to be 1.12 with a range of 1.00 ${\sim}$ 1.35, therefore, the cell was shown slightly elongated. Based on their morphology, the causative organisms of red tides in three different Korean waters were identified as P. bipes f. occultatum, which was reported for the first time in Korea.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.282-282
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• 2011

Low power consuming operation of phase-change random access memory (PRAM) can be achieved by confining the switching volume of phase change media into nanometer scale. Ge2Sb2Te5 (GST) is one of the best materials for the phase change random access memory (PRAM) because the GST has two stable states, namely, high and low resistance values, which correspond to the amorphous and crystalline phases of GST, respectively. However, achieving the fast operation speed at lower current requires an alternative chalcogenide material to replace the GST and shrinking the dimension of programmable volume. In this paper, we have fabricated nanoscale contact area on Ge2Sb2Te5 thin films with trimming process. The GST material was fabricated by melt quenching method and the GST thin films were deposited with thickness of 100 nm by the electron beam evaporation system. As a result, the reset current can be safely scaled down by reducing the device contact area and we could confirmed the phase-change characteristics by applying voltage pulses.

• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1347-1360
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• 2009

A multi-dimensional component for the thermal-hydraulic system analysis code, MARS, was developed for a more realistic three-dimensional analysis of nuclear systems. A three-dimensional and two-fluid model for a two-phase flow in Cartesian and cylindrical coordinates was employed. The governing equations and physical constitutive relationships were extended from those of a one-dimensional version. The numerical solution method adopted a semi-implicit and finite-difference method based on a staggered-grid mesh and a donor-cell scheme. The relevant length scale was very coarse compared to commercial computational fluid dynamics tools. Thus a simple Prandtl's mixing length turbulence model was applied to interpret the turbulent induced momentum and energy diffusivity. Non drag interfacial forces were not considered as in the general nuclear system codes. Several conceptual cases with analytic solutions were chosen and analyzed to assess the fundamental terms. RPI air-water and UPTF 7 tests were simulated and compared to the experimental data. The simulation results for the RPI air-water two-phase flow experiment showed good agreement with the measured void fraction. The simulation results for the UPTF downcomer test 7 were compared to the experiment data and the results from other multi-dimensional system codes for the ECC delivery flow.

• Journal of Haehwa Medicine
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• v.10 no.1
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• pp.365-374
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• 2001

The brain is one of the most complex systems in nature. Brain waves, or the "EEG", are electrical signals that can be recorded from the brain, either directly or through the scalp. The kind of brain wave recorded depends on the behavior of the animal, and is the visible evidence of the kind of neuronal (brain cell) processing necessary for that behavior. But, EEG had been considered as a virtually infinite-dimensional random signal. However, nonlinear dynamics light on dynamical aspects of the human EEG. The methods of nonlinear dynamics provide excellent tolls for the study of multi-variable, complex system such as EEG. In this study, 20 persons seperated in 2 groups were examined with EEG, one group stimulated on specific area of the sole of the foot with footbed inside the shoes. This experiment resulted in at the group stimulated on specific area of the sole of the foot correlation dimension of P4 and O1 channels increased significantly. Therefore. we obserbed that stimulation on specific area of the body had a constant effections on the specific channels.

• Journal of Korean Institute of Industrial Engineers
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• v.28 no.4
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• pp.360-367
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• 2002

The machine-part group formation is to group the sets of parts having similar processing requirements into part families, and the sets of machines needed to process a particular part family into machine cells. The purpose of this study is to develop a two-phase machine-part group formation algorithm based on Self-Organizing Maps (SOM). In phase I, it forms machine cells from the machine-part incidence matrix by means of SOM whose output layer is one-dimension and the number of output nodes is the twice as many as the number of input nodes in order to spread out the input vectors. In phase II, it generates part families which are assigned to machine cells by means of machine ratio related with processing part and it gives machine-part group formation. The proposed algorithm performs remarkably well in comparison with many well-known algorithms for the machine-part group formation problems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.9
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• pp.918-926
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• 1992

In this paper, ferrite-core loop antenna for portable radio receiver is designed and its characteristics are analyzed. Antenna is fabricated by inserting the ferrite core inside the planar conductor loop$(10{\times}6{\times}15mm^3)$. Bandwidth and Q factor of fabricated antenna measure 0.55 MHz and 280, respectively. These results show remarkable enhancement compared to the conventional loop antenna having the same physical dimension(BW=1.9MHz, Q=8.14). Experimental results show that the relative gain of the fabricated antenna is about 11 dB higher than that of the conventional antenna.