• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.11
• /
• pp.1121-1127
• /
• 2014

In this paper, a planar frequency reconfigurable antenna is proposed with variable capacitors. The proposed one is designed with a planar monopole, and varies resonant frequencies by variable capacitive loading of a varactor diode. The equivalent circuit and electromagnetic(EM) simulation are utilized for the analysis at the variable characteristic design of the antenna, and the same radiation performance. The implemented frequency variable monopole antenna has been verified by comparing prototypes with designed capacitors and ones with biased varactor diodes. The proposed antenna has presented the resonant frequency variations from 2.25 GHz to 2.42 GHz.

• Journal of electromagnetic engineering and science
• /
• v.17 no.4
• /
• pp.202-207
• /
• 2017

This paper presents the performance of a planar, low-profile, and wide-gain-bandwidth leaky-wave slit antenna in different thickness values of high-permittivity gallium arsenide substrates at terahertz frequencies. The proposed antenna designs consisted of a periodic array of $5{\times}5$ metallic square patches and a planar feeding structure. The patch array was printed on the top side of the substrate, and the feeding structure, which is an open-ended leaky-wave slot line, was etched on the bottom side of the substrate. The antenna performed as a Fabry-Perot cavity antenna at high thickness levels ($H=160{\mu}m$ and $H=80{\mu}m$), thus exhibiting high gain but a narrow gain bandwidth. At low thickness levels ($H=40{\mu}m$ and $H=20{\mu}m$), it performed as a metasurface antenna and showed wide-gain-bandwidth characteristics with a low gain value. Aside from the advantage of achieving useful characteristics for different antennas by just changing the substrate thickness, the proposed antenna design exhibited a low profile, easy integration into circuit boards, and excellent low-cost mass production suitability.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.10
• /
• pp.799-804
• /
• 2018

In this paper, a method for measuring the dielectric constant of a planar dielectric substrate using the free space material constant measurement method in a general measurement environment is proposed. Two horn antennas and a network analyzer were used for S-parameter measurement and the transmission and reflection coefficients of a planar dielectric substrate were calculated from the measurement results. To obtain a reliable dielectric constant in a low-precision-measurement environment, only the magnitude of the transmission coefficient, which has a small error due to the measurement environment, is used for dielectric constant estimation. Finally, the dielectric constant is determined by comparing the measured results at different frequencies.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.4
• /
• pp.199-204
• /
• 2016

This paper was proposed floating island power MOSFET for lowering on state resistance and the proposed device was maintained 600 V breakdown voltage. The electrical field distribution of floating island power MOSFET was dispersed to floating island between P-base and N-drift. Therefore, we designed higher doping concentration of drift region than doping concentration of planar type power MOSFET. And so we obtain the lower on resistance than on resistance of planar type power MOSFET. We needed the higher doping concentration of floating island than doping concentration of drift region and needed width and depth of floating island for formation of floating island region. We obtained the optimal parameters. The depth of floating island was $32{\mu}m$. The doping concentration of floating island was $5{\times}1,012cm^2$. And the width of floating island was $3{\mu}m$. As a result of designing the floating island power MOSFET, we obtained 723 V breakdown voltage and $0.108{\Omega}cm^2$ on resistance. When we compared to planar power MOSFET, the on resistance was lowered 24.5% than its of planar power MOSFET. The proposed device will be used to electrical vehicle and renewable industry.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.8
• /
• pp.486-489
• /
• 2015

Power semiconductor device has a very long history among semiconductor, since the invention of low-pressure bipolar transistor 1947, and so far from small capacity to withstand voltage-current, high-speed and high-frequency characteristics have been developed with high function. In this study, the PWM IC Switch to the main parts used in IGBT (insulated gate bipolar transistor) for the low power loss and high drive capability of the simulator to Synopsys' T-CAD used by the 1,700 V NPT Planar IGBT, 1,700 V FS was a study of the Planar IGBT, the results confirmed that IGBT 1,700 V FS Planar is making about 11 percent less than the first designed NPT Planar IGBT.

• Geomechanics and Engineering
• /
• v.14 no.3
• /
• pp.233-240
• /
• 2018

Pullout tests are usually employed to determine the ultimate bearing capacity of reinforced soil, and the load-displacement curve can be obtained easily. This paper presents an analytical solution for predicting the full-range mechanical behavior of a buried planar reinforcement subjected to pullout based on a bi-linear bond-slip model. The full-range behavior consists of three consecutive stages: elastic stage, elastic-plastic stage and debonding stage. For each stage, closed-form solutions for the load-displacement relationship, the interfacial slip distribution, the interfacial shear stress distribution and the axial stress distribution along the planar reinforcement were derived. The ultimate load and the effective bond length were also obtained. Then the analytical model was calibrated and validated against three pullout experimental tests. The predicted load-displacement curves as well as the internal displacement distribution are in closed agreement with test results. Moreover, a parametric study on the effect of anchorage length, reinforcement axial stiffness, interfacial shear stiffness and interfacial shear strength is also presented, providing insights into the pullout behaviour of planar reinforcements of MSE structures.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.2
• /
• pp.248-258
• /
• 1992

Three-dimensional rigid-plastic finite element formulation based on the membrane theory was described and a computer program for large deformation analysis was developed. In the formulation, normal and planar anisotropy of sheet material and rotation of the principal axes of anisotropy was taken into consideration. Sheet metal was assumed to be rigid-plastic material obeying Hill's quadratic yield criterion and its associated flow rule. Deep drawing process, as a preliminary test, for normal anisotropic material was analyzed in order to examine the validity of developed finite element program. The results were consistent with the existing finite element solutions or experimental data. The present study was mainly concerned with the influence of planar anisotropy on deformation behaviour. Finite element analysis and experiment were carried out for the whole process of deep drawing of planar anisotropic material. The computational and experimental results on the shape of ear, strain distribution and punch load were in good agreement.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2009.01a
• /
• pp.482-486
• /
• 2009

Scale-invariant feature is an effective method for retrieving and classifying images. In this study, we analyze a scale-invariant planar curve features for developing 2D shapes. Scale-space filtering is used to determine contour structures on different scales. However, it is difficult to track significant points on different scales. In mathematics, curvature is considered to be fundamental feature of a planar curve. However, the curvature of a digitized planar curve depends on a scale. Therefore, automatic scale detection for curvature analysis is required for practical use. We propose a technique for achieving automatic scale detection based on difference of curvature. Once the curvature values are normalized with regard to the scale, we can calculate difference in the curvature values for different scales. Further, an appropriate scale and its position are detected simultaneously, thereby avoiding tracking problem. Appropriate scales and their positions can be detected with high accuracy. An advantage of the proposed method is that the detected significant points do not need to be located in the same contour. The validity of the proposed method is confirmed by experimental results.

• Korea-Australia Rheology Journal
• /
• v.13 no.3
• /
• pp.131-139
• /
• 2001

A coupled approach is proposed for the prediction of sheet profile in sheet casting process, which combines one-dimensional analytical method on planar elongational flow region and three-dimensional numerical method on the other region. The strategy is constructed from the observations that the flow domain of sheet casting process can be separated into two parts based old the flow kinematics. The flow field in the central region of sheet, over which the planar elongational flow dominates, is possibly replaced by one-dimensional analytical solution. Then only a partial flow domain near the edge region of sheet, where the flow kinematics cannot be described by the planar elongational flow itself, requires three-dimensional numerical simulation. Good agreement is observed between the coupled approach developed in this study and the full three-dimensional numerical simulation previously developed and reported by the authors. This coupled approach may have provided flexibility with low costs to accommodate a wide range of die sizes in sheet casting process.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.10
• /
• pp.1365-1372
• /
• 2001

In the planar flow casting(PFC) process, the conditions of the melt puddle between nozzle and rotating wheel affect significantly the quality and dimensional uniformity of the downstream ribbon. For stable puddle formation, the nozzle is placed very close to the quenching wheel, so the surface-tension and wall-adhesion forces have an important effect upon the fluid flow.\`In this study the planar flow casting process has been mode]ed using the VOF method for free surface tracking. The transient puddle formation from the present analysis shows good agreements with the previous experimental results. Furthermore, the variation of melt temperature and the corresponding cooling rate of the melt have been examined. The present results also show how the melt puddle can be farmed on the rotating substrate, how the melt flows within the puddle, and how the changes of the process variables affect the puddle formation and its corresponding fluid flow and heat transfer behavior.