• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.7
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• pp.987-994
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• 2013

In this paper, a dual-band open-ended circular ring moNopole antenna for WLAN(Wireless Local Area Networks) applications. The proposed antenna is based on a planar moNopole design, and composed of open-ended one circular ring of radiating patches for dual-band operation. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that effect antenna characteristics. Using the obtained parameters, the proposed antenna is fabricated. The fabricated antenna is measured at the operating frequencies(2.4-2.484 GHz, 5.15-5.825 GHz), and the return loss coefficient, gain, and radiation patterns are determined.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.84-90
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• 2022

Hydraulic coupling systems play an important role in easily connecting or disconnecting pipes or hoses that transmit high-pressure fluids without hydraulic oil leakage in hydraulic power transmission equipment. A flat-face hydraulic quick coupler is a recently developed product that can reduce environmental pollution by minimizing hydraulic oil leakage during connection and disconnection. In this study, the influence of the shape of the inner ring of a 3/8" flat-face hydraulic quick coupler on its internal flow characteristics was analyzed and evaluated by numerical analysis based on computational fluid dynamics. The flow velocity distribution, temperature distribution, and optimal shape design of the inner ring were obtained by comparing the results of the flow characteristics, such as the pressure drop.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.305-311
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• 2012

For the optimization of the fundamental natural frequency of stiffened cylindrical shells, simulations were performed for cylindrical shells that were stiffened with between one and five ring stiffeners. ANSYS 11.0 was used to simulate the optimization for the natural frequency. The Subproblem Approximation Method was applied as the optimization method. The design function of the optimization was the geometry of the T-shaped ring stiffener, and the constraint function was the maximum additional volume, constrained to a 10% increase. The objective function of the optimization was chosen to maximize the fundamental natural frequency. The performance index for optimal design was defined as the ratio of the natural frequency to the volume of the unstiffened and stiffened shells. The optimal performance index was obtained for the shell stiffened with three rings.

• Journal of the Korean Institute of Gas
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• v.3 no.3 s.8
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• pp.58-64
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• 1999

This paper has been analyzed for the stress behavior problems of the ring knot membrane unit using the finite element method about the pitch design of the membrane unit, which is one of the most important parameters in manufacturing of the membrane type LNG storage tanks. The FEM results have been compared those of the existing pitch design length. The safety problem of the ring knot membrane model, which is considered in this study, does not come out any more no matter what the pitch length is used in the extra large LNG storage tanks. But in the case of the membrane for LNG tankers, it is advantageous to design the pitch short because of fatigue strength caused by repeated loadings. Looking at the deformation behaviors of the membrane corrugation, the deformation of the hight in the y direction occurs $15{\~}50\%$ more than that of the width in the z direction. It shows also that the deformation of the membrane with $-162^{\circ}C$ cryogenic temperature is not so great compared with the deformation by hydrostatic pressure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.19-22
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• 2003

In this study, the design of prestressed die for spur gear forging have been investigated. The stress concentration at notch of the die insert is very important in the design of die for the forging of spur gear such as non-axisymmetric geometry. In the previous study, the flexible tolerance method was used in order to search the optimal value of design variables considering the constrain conditions. In the design process, it was also involved the safety factor to the yield strength of each ring by considering allowable tensile or compressive hoop stress in each ring. Using this technique, the die deign for spur gear forging has been successfully performed without yielding of the die after shrink fitting and during forging.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.2
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• pp.406-417
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• 2014

This paper presents a numerical optimization method to improve the performance of the propeller with Turbo-Ring using real-coded genetic algorithm. In the presented method, Unimodal Normal Distribution Crossover (UNDX) and Minimal Generation Gap (MGG) model are used as crossover operator and generation-alternation model, respectively. Propeller characteristics are evaluated by a simple surface panel method "SQCM" in the optimization process. Blade sections of the original Turbo-Ring and propeller are replaced by the NACA66 a = 0.8 section. However, original chord, skew, rake and maximum blade thickness distributions in the radial direction are unchanged. Pitch and maximum camber distributions in the radial direction are selected as the design variables. Optimization is conducted to maximize the efficiency of the propeller with Turbo-Ring. The experimental result shows that the efficiency of the optimized propeller with Turbo-Ring is higher than that of the original propeller with Turbo-Ring.

• Tribology and Lubricants
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• v.27 no.5
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• pp.240-248
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• 2011

Mechanical face seal installed in primary heat transport pump used for heavy water reactor prevents leakage of working fluid using thin working fluid film between primary seal ring and mating ring. If the leakage of working fluid exceeds the allowable volume, serious accident can be happened by the trouble of primary heat transport pump. The thinner fluid film exists between primary seal ring and mating ring, the less working fluid leaks out. On the other hand, if the thickness of fluid film is not enough, the life of mechanical face seal will be reduced by friction and wear. Therefore appropriate design is necessary to maximize the performance and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to investigate the performance of mechanical face seals which have same deep straight groove and 11 different net coning values. As results, equilibrium clearance between primary seal ring and mating ring, leakage volume of working fluid, friction torque on sealing surface and stiffness of working fluid film were obtained. With increasing net coning value, equilibrium clearance and leakage volume increase, and friction torque and stiffness of fluid film decrease.

• Journal of Korean Society of Steel Construction
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• v.30 no.1
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• pp.25-35
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• 2018

Resisting strength of ring-stiffened cylindrical steel shell under uniform external pressure was evaluated by geometrically and materially nonlinear finite element method. The effects of shape and amplitude of geometric initial imperfection, radius to thickness ratio, and spacing of ring stiffeners on the resisting strength of ring-stiffened shell were analyzed. The resisting strength of ring-stiffened cylindrical shells made of SM490 obtained by FEA were compared with design strengths specified in Eurocode 3 and DNV-RP-C202. The shell buckling modes obtained from a linear elastic bifurcation FE analysis were introduced in the nonlinear FE analysis as initial geometric imperfections. The radius to thickness ratios of cylindrical shell in the range of 250 to 500 were considered.

• Journal of IKEEE
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• v.11 no.4
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• pp.235-238
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• 2007

The planar edge termination techniques of field-ring and deep junction field-ring were investigated and optimized using a two-dimensional device simulator TMA MEDICI. By trenching the field ring site which would be implanted, a better blocking capability can be obtained. The results show that the p-n junction with deep junction field-ring can accomplish near 30% increase of breakdown voltage in comparison with the conventional field-rings. The deep junctionfield-rings are easy to design and fabricate and consume same area but they are relatively sensitive to surface charge. Extensive device simulations as well as qualitative analyses confirm these conclusions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.371-375
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• 2000

In this paper a new conductivity modulated power transistor called the Lateral Insulated Gated Bipolar Transistor which included n+ ring and p-channel gate is presented. A new lateral IGBT structure is proposed to suppress latch-up and to improve turn off time by imploying n+ ring and p-channel gate and verified by MEDICI. The simulated I-V characteristics at $V_{G}$=15V show that the latch up occurs at $V_{A}$=18V and 6.9$\times$10$^{-5}$ A/${\mu}{\textrm}{m}$ for the proposed LIGBT while the conventional LIGBT latches at $V_{A}$=1.3V and 1.96${\mu}{\textrm}{m}$10$^{-5A}$${\mu}{\textrm}{m}$. It is shown that turn off characteristic of new LIGBT is 8 times than that of conventional LIGBT. And noble LIGBT is not n+ buffer layer because that It includes p channel gate and n+ ring. Therefore Mask for the buffer layer isn’t needed. The concentration of n+ ring is and the numbers of n+ ring and p channel gate are three for the optimal design.n.n.n.n.