• Journal of the Institute of Convergence Signal Processing
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• v.16 no.3
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• pp.102-107
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• 2015

Personal information leakage is one of the great recent issues, which can be caused by hacking or censorship when a messenger program is used between user groups in Android-based smartphones, In order to solve these problems, companies generally apply complex security procedures inside the messenger, but which degrade the efficiency of work. This paper proposes a method which can improve work efficiency and strengthen security by allowing only the clients that can access a particular AP, and implementing a closed messenger group. The proposed method is validated by implementing on the Android-based smartphones.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1708-1714
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• 2011

AT feeding system of the electric railway system is installed every about 10km at between the feeder and catenary in parallel and the mid-point of the transformer is connected to the rail The supply voltage of this system is doubled than rolling stock voltage. So the voltage drop is smaller than usual. And the other merit of this system is the decreasing inductive disturbance to the communication line because of the reduced current in rail which runs reversed in a point of view of rolling stock. Also, ATP(Auto Transformer Post) is installed to reduce the voltage drop and to mitigate the inductive disturbance, but still now the proper distance between the ATP and AT feeding system is not established which ranges from 2 to 10[km]. The stable result of simulation(which is set that the end of the line AT is installed) to the voltage drop and inductive disturbance can not analyzes the effect to the supply system due to the ATP. This paper analyzes the effect to the system depending on the location of ATP by forecasting the voltage drop and inductive disturbance.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.1-7
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• 2015

As energy consumption of building and the reduction of carbon dioxide emissions have been emphasized, phase change materials(PCM) have been introduced as building materials due to its high heat storage performance. Using shape-stabilizing technique, octadecane/xGnP shape-stabilized PCM(SSPCM) can prevent leakage and improve heat storage performance. The objectives of this study are to propose mix design method of concrete mixed with SSPCM and to evaluate mechanical behaviors of the concrete mixed with SSPCM manufactured according to the proposed mix design. Based on the previously reported material test result, the existing mix design of plain concrete(Concrete standard specification, 2009) is modified to consider reduction of strength in concrete due to the addition of SSPCM. To verify the proposed mix design, specimens are fabricated according to the proposed mix design and axial strength tests and three-point loading tests are performed. Test results show that compressive strengths of the tested specimens reach the designed strength even when two different mix ratios of SSPCM are used. From three-point loading tests, flexural stresses decrease as mix ratio of SSPCM increases.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1654-1663
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• 2015

Compared to LC resonance, LCL resonance has distinct advantages such as a large resonant capability, low voltage and current stresses of the power device, constant voltage or current output characteristics, and fault-tolerance capability. Thus, LCL resonant compensation is employed for a movable Inductive Contactless Power Transfer (ICPT) system with a multi-load in this paper, which achieves constant current output characteristics. Peculiarly, the primary side adopts a much larger compensation inductor than the primary leakage inductor to lower the reactive power, reduce the input current ripple, generate a large current in the primary side, and realize soft-switching. Furthermore, this paper proposes an approximate resonant point for large inductor-ratio LCL resonant compensation through fundamental wave analysis. In addition, the PWM control strategy is used for this system to achieve constant current output characteristics. Finally, an experimental platform is built, whose secondary E-Type coils can ride and move on a primary rail. Simulations and experiments are conducted to verify the effectiveness and accuracy of both the theory and the design method.

• Journal of the Korean Ceramic Society
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• v.33 no.6
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• pp.665-671
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• 1996

Ferroelectric Pb(Fe1/2Nb1/2)O3 thin films were successfully fabricated on ITO/Glass substrate by sol-gel proces-sing and characterized to determine the dielectric and electric properties. Viscosity of PEN sol measured to investigate rheological properties was 3.25 cP which was proper for coating. The sol also showed Newtonian behavior. RTA(Rapid Thermal Annealing) was used for the annealing of the thin film and 1200~1700$\AA$ thick PEN thin films were fabricated by repeating the intermediate and the final annealing. After the deposition of Pt as top electrode by vacuum evaporation dielectric and electric properties were measured. Dielectric properties of FFN thin film were enhanced by increasing the perovskite phase fraction with increasing the annealing temperature. Measured dielectric constant of 1700$\AA$ PFN thin film annealed at $650^{\circ}C$ was 890 at 1kHz Capacitatnce density and dielectric loss were 47 fF/${\mu}{\textrm}{m}$2 and 0.47 respectively. As a result of measuring Curie temperature PFN thin films had Curie point with a rang of 110~12$0^{\circ}C$ and showed broad dielectric peak at that point. Leakage current of the PFN thin films were increased with increasing the annealing tempera-ture.

• Journal of Drive and Control
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• v.12 no.4
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• pp.8-14
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• 2015

A quick-acting hydraulic fuse, which is mainly composed of a poppet, a seat, and a spring, must be designed to minimize the leaked oil volume during fuse operation on a line rupture. The optimal design parameters of a quick-acting hydraulic fuse were searched using the design of experiments method and the complex method. First, the $L_{50}(5^4)$ orthogonal array is used to find the robust minimum point among the 625 points of design variables. The search range can then be narrowed around the robust minimum point. Second, the $L_{25}(5^4)$ orthogonal array is used to obtain the variations of the design variables in the narrowed search range. The variations of design variables are used to set the structure of a polynomial equation representing the leakage oil volume of the quick-acting hydraulic fuse. The least squares method is then applied to obtain the coefficients of polynomial equation. Finally, the complex method is used to find the optimal design parameters where the objective function is described by the polynomial equation.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2202-2211
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• 2016

In certain applications, such as IPT-based EV charger (IPTEC), any variation in alignment and distance between pickup and charger primary leads to a change in leakage and magnetic impedance magnitudes. The power transmission capacity is not always at the maximum level because of these variations. This study proposes a new low-cost tracking method that achieves the Maximum Inductive Power Transmission Capacity (MIPTC). Furthermore, in the proposed method, the exchange of information between load and source is not required. For an application such as IPTEC, the load detected by the IPTEC varies continuously with time because of the change in state of the charge. This load variation causes a significant variation in IPT resonant circuit voltage gain. However, the optimized charging output voltage should be kept constant. From the analysis of the behavior of the IPT circuit at different working frequencies and load conditions, a MIPTC operation point that is independent of load condition can be identified. Finally, the experimental results of a developed prototype IPT circuit test show the performance of the proposed method.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.335-336
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• 2014

This paper investigates the design of coupled inductor for minimum inductor current ripple in rapid traction battery charger systems. Based on the general circuit model of coupled inductor together with the operating principles of dc-dc converter, the relationship between the ripple size of inductor current and the coupling factor is derived under the different duty ratio. The optimal coupling factor which corresponds to a minimum inductor ripple current becomes -1, i.e. a complete inverse coupling without leakage inductance, as the steady-state duty ratio operating point approaches 0.5. In an opposite manner, the optimal coupling factor value of zero, i.e. zero mutual inductance, is required when the steady-state duty ratio operating point approaches either zero or one. Coupled inductors having optimal coupling factor can minimize the ripple current of inductor and battery current resulting in a reliable and efficient operation of battery chargers.

• International Journal of Vascular Biomedical Engineering
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• v.1 no.2
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• pp.20-29
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• 2003

A new treatment for coronary artery occlusive disease is being developed in which a shunt or conduit is placed directly connecting the left ventricle with the diseased artery at a point distal to the obstruction. To aid in assessing and optimizing its benefit, a computational model of the cardiovascular system was developed and used to explore various design conditions. Simulation results indicate that in complete LAD occlusion, flow can be returned to approximately 65% of normal if the conduit resistance is equal for forward and reverse flow, increasing to 80% in the limit in which backflow resistance is infinite. Increases in flow rate produced by asymmetric flow resistance are considerably enhanced in the case of a partial LAD obstruction since the primary effect of resistance asymmetry is to prevent leakage back into the ventricle("steal") during diastole. Increased arterial compliance has little effect on net flow with a symmetric shunt, but leads to considerable augmentation when the resistance is asymmetric. These results suggest that an LV-LAD conduit will be beneficial when stenosis resistance(Rst) > 27 PRU if resistance is symmetric.

• Journal of Chest Surgery
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• v.37 no.12
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• pp.1029-1031
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• 2004

We had expierienced pulmonary lymphangioleiomyomatosis(LAM) with bilateral chylothorax and chylous ascites. A twenty-one-year-old lass with chief complaint of abdominal pain was admitted through the emergency room. She received emergent pelvicoscopic surgery for the rupture of the right corpus luteum. We aspirated 1000ml of the uncoagulated blood. The bleeding point was cautherized electrically. LAM was diagnosed with tissue from the retroperitoneum. Chylous ascites and bilateral chylothorax were occurred despite of various treatments. On thoracotomy, bullous changed lung and lymphatic leakage from visceral and parietal pleura were observed. She died of respiratory insufficiency and general weakness after 6 months from admission.