• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.993-998
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• 2017

In this paper, a high-accuracy current sensing technique for three-phase current paths in an electrical switchboard is proposed. Conventional open-style current sensors using magnetic sensors show inaccurate sensing performance with more than 10% error due to undesired magnetic field interference from neighboring paths. To increase accuracy, large and expensive current transformers with large permeabilities have been used, which increased the cost and size. The proposed technique can improve the measured magnetic field by the calculation of magnetic interference effect from neighboring current paths. The relationship between neighboring magnetic fields and the desired magnetic field is theoretically analyzed in a general case. The proposed technique is verified using magnetic field simulations in a three-phase busbar environment.

• Journal of Radiation Protection and Research
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• v.3 no.1
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• pp.6-22
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• 1978

High energy electron beams took effect for tumor radio-therapy, however, had a lot of problems in clinical application because of various conversion factors and complication of physical reactions. Therefor, we had experimentally studied the important properties of high energy electron beams from the linear accelerator, LMR-13, installed in Yonsei Cancer Center. The results of experimental studies on the problems in the 8, 10, 12 Mev electron beam therapy were reported as following. 1. On the measurements of the outputs and absorbed doses, the ionization type dosimeters that had calibrated by $^{90}Sr$ standard source were suitable as under 3% errors for high energy electrons to measure, but measuring doses in small field sizes and the regions of rapid fall off dose with ionization chambers were difficult. 2. The electron energy were measured precisely with energy spectrometer consisted of magnet analyzer and tele-control detector and the practical electron energy was calculated under 5% errors by maximum range of high energy electron beam in the water. 3. The correcting factors of perturbated dose distributions owing to radiation field, energy and material of the treatment cone were checked and described systematically and variation of dose distributions due to inhomogeneous tissues and sloping skin surfaces were completely compensated. 4. The electron beams, using the scatterers; ie., gold, tin, copper, lead, aluminium foils, were adequately diffused and minimizing the bremsstrahlung X-ray induced by the electron energy, irradiation field size and material of scatterers, respectively. 5. Inproving of the dose distribution from the methods of pendulum, slit, grid and focusing irradiations, the therapeutic capacity with limited electron energy could be extended.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1149-1164
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• 1997

In this study, the applicability of the RNG k-.epsilon. model to the analysis of the complex flows is studied. The governing equations based on a non-orthogonal coordinate formulation with Cartesian velocity components are used and discretized by the finite volume method with non-staggered variable arrangements. The predicted results using the RNG k-.epsilon. model of three complex flows, i.e., the flow over a backward-facing step and a blunt flat plate, the flow around a 2D model car are compared to these from the standard k-.epsilon. model and experimental data. That of the unsteady axisymmetric turbulent flow within a cylinder of reciprocating model engine including port/valve assembly and the spray characteristics within a chamber of direct injection model engine are compared to these from the standard k-.epsilon. model and experimental data. The results of reattachment length, separated eddy size, average surface pressure distribution using the RNG k-.epsilon. model show more reasonable trends comparing with the experimental data than those using the modified k-.epsilon. model. Although the predicted rms velocity using the modified k-.epsilon. model is lower considerably than the experimental data in incylinder flow with poppet valve, predicted axial and radial velocity distributions at the valve exit and in-cylinder region show good agreements with the experimental data. The spray tip penetration predicted using the RNG k-.epsilon. model is more close to the experimental data than that using the modified k-.epsilon. model. The application of the RNG k-.epsilon. model seems to have some potential for the simulations of the unsteady turbulent flow within a port/valve-cylinder assembly and the spray characteristics over the modified k-.epsilon. model.

• Journal of Internet Computing and Services
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• v.18 no.1
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• pp.21-26
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• 2017

In this paper, an USB-OTG (Uiversal Serial Bus On-the-go) interface module was designed with the iris information for personal identification. The image recognition algorithm which was searching face and iris areas, was proposed with pixel differences from eye blinking after several facial images were captured and then detected without any activities like as pressing the button of smart phone. The region of pupil and iris could be fast involved with the proper iris area segmentation from the pixel value calculation of frame difference among the images which were detected with two adjacent open-eye and close-eye pictures. This proposed iris recognition could be fast processed with the proper grid size of the eye region, and designed with the frame difference between the adjacent images from the USB-OTG interface with this camera module with the restrict of searching area in face and iris location. As a result, the detection time of iris location can be reduced, and this module can be expected with eliminating the standby time of eye-open.

• Journal of Korean Society of Rural Planning
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• v.18 no.1
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• pp.9-15
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• 2012

This study used GIS method for the characteristic analysis of farmstead location in study area. The present study surveyed the coordinates of location for 76 livestock farmsteads with big size in rural areas within city of Cheonan. Based on the surveyed data, this study analyzed the spatial characteristics of location for the farmsteads by using both new evaluation criteria and their corresponding GIS (geographic information system) layers developed in this research. The criteria consist of six factors, which are 2 geographic factors for slope(SLO) and aspect(ASP) of earth surface, 3 accessability factors for distance from water area(DWA), road(DRO), and built-up area(DBA), including type of landuse(TLA). In the analysis results of six criteria using the grid funcations of GIS, the highest distributed ratios of the farmsteads per criterion were found at the lower slope area less then 2% in SLO, the area with south and south-east direction in ASP, the area with distance between 500m and 1,000m in both DWA and DRO, the area within 500m in DWA, and the paddy and upland area in TLA. As new finding of this study, these analysis results seemed that the farmsteads have been located at the better places with the priority to build and manage conveniently and economically.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.7-7
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• 2009

Lead telluride (PbTe) is a very promising thermoelectric material due to its narrow band gap (0.31 eV at 300 K), face-centered cubic structure and large average excitonic Bohr radius (46 nm) allowing for strong quantum confinement within a large range of size. In this work, we present the thermoelectric properties of individual single-crystalline PbTe nanowires grown by a vapor transport method. A combination of electron beam lithography and a lift-off process was utilized to fabricate inner micron-scaled Cr (5 nm)/Au (130 nm) electrodes of Rn (resistance of a near electrode), Rf (resistance of a far electrode) and a microheater connecting a PbTe nanowire on the grid of points. A plasma etching system was used to remove an oxide layer from the outer surface of the nanowires before the deposition of inner electrodes. The carrier concentration of the nanowire was estimated to be as high as $3.5{\times}10^{19}\;cm^{-3}$. The Seebeck coefficient of an individual PbTe nanowire with a radius of 68 nm was measured to be $S=-72{\mu}V/K$ at room temperature, which is about three times that of bulk PbTe at the same carrier concentration. Our results suggest that PbTe nanowires can be used for high-efficiency thermoelectric devices.

• Journal of Korean Society of Forest Science
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• v.98 no.6
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• pp.764-771
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• 2009

This research aimed at analyzing relationship between spatial distribution of Pinus densiflora, and topographical factors in Seorak and Chiak national park. 100 m grid size was proven to be suitable for analyzing spatial distribution characteristics of Pinus densiflora. Pinus densiflora appeared mainly on 400 m~800 m of elevation, $15^{\circ}{\sim}30^{\circ}$ of slope and 0~2 of TWI. There were no big differences in appearance frequency of Pinus densiflora area by aspect. There were differences in distribution characteristics of Pinus densiflora between below and above 400 m of elevation. There were no big differences in appearance frequency of Pinus densiflora area above 400 m of elevation but a big differences by topographical factors below 400 m of elevation.

• Journal of computational fluids engineering
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• v.17 no.3
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• pp.75-86
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• 2012

We developed a preliminary CFD analysis methodology to predict a pressure build up due to hydrogen flame acceleration in the APR1400 IRWST on the basis of CFD analysis results for test data of hydrogen flame acceleration in a scaled-down test facility performed by Korea Atomic Energy Research Institute. We found out that ANSYS CFX-13 with a combustion model of the so-called turbulent flame closure and a model constant of A = 5.0, a grid model with a hexahedral cell length of 5.0 mm, and a time step size of $1.0{\times}10^{-5}$ s can be a useful tool to predict the pressure build up due to the hydrogen flame acceleration in the test results. Through the comparison of the simulated results with the test results, we found out that the proposed CFD analysis methodology enables us to predict the peak pressure within an error range of about ${\pm}29%$ for the hydrogen concentration of 19.5%. However, the error ranges of the peak pressure for the hydrogen concentration of 15.4% and 18.6% were about 66% and 51%, respectively. To reduce the error ranges in case of the hydrogen concentration of 15.4% and 18.6%, some uncertainties of the test conditions should be clarified. In addition, an investigation for a possibility of flame extinction in the test results should be performed.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.382-387
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• 2005

Polyvinylidene fluoride (PVDF) surface was irradiated and became superhydrophilic by low energy (180 eV) and high flux $(\~10^{15}/cm{\cdot}s)$ ion beam. As an ion source, a closed electron Hall drift thruster of $\phi=70mm$ outer channel size without grid was adopted. Ar, $O_2$ and $N_2O$ were used for source gases. When $N_2O^+$ and $O_2^+$ reactive gas ion beam were irradiated with the ion fluence of $5\times10^{15}/cm^2$, the wetting angle for deionized water was drastically dropped from $61^{\circ}\;to\;4^{\circ}\;and\;2^{\circ}$, respectively. Surface energy was also increased up to from 44 mN/m to 81 mN/m. Change of chemical component in PVDF surface was analyzed by x-ray photoelectron spectroscopy. Such a great increase of the surface energy was intimately related with the increase of hydrophilic group component in reactive ion irradiated PVDF surfaces. By using an atomic force microscopy, the root-mean-square of surface roughness of ion irradiated PVDF was not much altered compared to that of pristine PVDF.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.735-744
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• 2016

This study attempted quantitative analysis by space syntax on the plan of a non-hierarchical arrangement, which selected SANAA's work after Almere Stadt Theater, and analyzed the difference in the quantitative value of the non-hierarchical arrangement in plan that appears externally. The analysis results were as follows. First, SANAA's spaces with a non-hierarchical arrangement plan that appears externally showed a definite quantitative value difference, and had a hierarchical space difference in the plan that does not appear externally. Second, the spaces with a high integration value also had a high connectivity value, which is indicated by increasing the number of space openings using the method of giving hierarchy to the non-hierarchical arrangement plan or adjusting the size of the room or location to grant hidden hierarchy. Third, SANAA used exterior corridor rather than interior corridor in grid-type plan to solve the accessibility problem, and the open coat spaces between rooms provide natural lighting and ventilation and are used as equipment that controls the hidden hierarchy of space at the same time.